Carbon footprint quantified lubricating oil composition and preparation method thereof

Abstract

The invention relates to a carbon footprint quantified lubricating oil composition which comprises the following components in parts by weight: 60-75 parts of rerefined base oil, 8-15 parts of auxiliary base oil, 4-8 parts of alkyl naphthalene, 3-6 parts of a viscosity index improver and 0.12-0.30 part of a polymethacrylate pour point depressant, wherein the viscosity index improver is selected from polymethacrylate of which the glass transition temperature is not higher than 20 DEG C, and the auxiliary base oil is dibasic acid diester and / or polyol ester of which the carbon chain length is C8-C10. According to the scheme, the technical effects of low-temperature performance and low-carbon footprint are achieved, and the lubricating performance and the stability are both considered.

Description

Technical Field

[0001] This invention relates to the field of lubricating oil composition technology, and in particular to a lubricating oil composition with quantified carbon footprint and its preparation method. Background Technology

[0002] As an indispensable functional material for mechanical equipment such as engines, gears, and hydraulic systems, lubricating oil's base oil formulation and additive system directly determine the fluidity of vehicles during low-temperature starting, energy efficiency during use, and environmental impact throughout its entire life cycle.

[0003] In existing technologies, polyalphaolefins (PAOs) are widely used in the preparation of high-end lubricating oils with excellent low-temperature performance due to their low pour point and excellent viscosity-temperature characteristics. However, PAOs are derived from petrochemical synthesis, resulting in high energy consumption and carbon emissions during production. Their carbon footprint is high in life-cycle assessments, which is detrimental to achieving the goals of the "dual carbon" policy. On the other hand, refined base oils (RRBOs), as products of waste lubricating oil recycling, have significant advantages in terms of carbon footprint. However, their low-temperature fluidity is limited by the residual n-alkane content, making it difficult to maintain CCS viscosity and MRV viscosity indicators in extremely cold environments.

[0004] To improve the low-temperature performance of RRBO-based lubricants, existing technologies often involve adding viscosity index improvers or pour point depressants. However, these methods alone are often insufficient to address issues such as wax crystal formation and excessively high viscosity at low temperatures. Furthermore, current modification methods primarily focus on performance improvement while lacking integration with quantification of the carbon footprint throughout the entire lifecycle, making it difficult to achieve verifiable carbon reduction effects while ensuring lubrication performance.

[0005] Therefore, there is an urgent need for a composite design that uses refined base oil as the main component and optimizes auxiliary base oils and various functional additives to achieve superior low-temperature fluidity compared to PAO-based lubricants, and to achieve a quantitative reduction in the product's carbon footprint throughout its entire life cycle under international standards such as ISO 14067, thereby balancing low-temperature performance, lubrication stability, and environmental friendliness. Summary of the Invention

[0006] This invention covers the following technical solutions: One aspect of the present invention relates to a carbon footprint quantified lubricating oil composition, comprising, by weight parts:

[0007] 60-75 parts of refined base oil (RRBO), 8-15 parts of auxiliary base oil, 4-8 parts of alkyl naphthalene, 3-6 parts of viscosity index improver, and 0.12-0.30 parts of polymethyl methacrylate pour point depressant (PPD);

[0008] The viscosity index improver is selected from polymethyl methacrylate (PMA) with a glass transition temperature not higher than -20 °C, and the auxiliary base oil is a diester of a dicarboxylic acid and / or a polyol ester with a carbon chain length of C8 to C10.

[0009] In this invention, the glass transition temperature is determined by differential scanning calorimetry (DSC) at a heating rate of 10 K / min.

[0010] In some embodiments, the auxiliary base oil has a kinematic viscosity of less than 10 mm² / s at 40 °C and a pour point not higher than -40 °C.

[0011] In some embodiments, the carbon footprint quantified lubricating oil composition further includes 0.3 to 1.0 parts of an antioxidant selected from hindered phenols, diaryl amines, and mixtures thereof.

[0012] In some embodiments, the carbon footprint quantified lubricating oil composition further includes 1.5 to 3.0 parts of a detergent-dispersant, wherein the detergent-dispersant is polybutene succinimide or a derivative thereof.

[0013] In some embodiments, the carbon footprint quantified lubricant composition further comprises 0.2 to 0.8 parts of an anti-wear agent, said anti-wear agent being zinc dialkyl dithiophosphate (ZDDP) and / or an organic molybdenum compound.

[0014] In some embodiments, the carbon footprint quantified lubricating oil composition further includes 0.1 to 0.6 parts of a friction modifier selected from fatty acid esters, nitrogen-containing organic compounds, and / or molybdenum disulfide derivatives.

[0015] In some embodiments, the carbon footprint quantified lubricating oil composition further includes 0.01 to 0.2 parts of an antifoaming agent selected from silicone or acrylate polymers.

[0016] In some embodiments, the carbon footprint quantified lubricating oil composition has a CCS viscosity of no more than 5000 mPa·s at -35 °C, and its carbon footprint is reduced by ≥10% compared to PAO-based compositions of the same viscosity grade under ISO 14067 life cycle assessment.

[0017] Another aspect of the present invention relates to a method for preparing a lubricating oil composition with carbon footprint quantification as described above, comprising:

[0018] (a) Mixing the refining base oil (RRBO) with the auxiliary base oil;

[0019] (b) Under stirring conditions, the other components are added sequentially;

[0020] (c) Heat and stir until the additives are fully dissolved to obtain a uniform and transparent lubricating oil composition.

[0021] In some embodiments, the heating is performed by controlling the mixing temperature to be between 45°C and 60°C.

[0022] This invention uses refined base oil (RRBO) as the main component, combined with auxiliary base oils (C8-C10 dicarboxylic acid diesters and / or polyol esters), alkyl naphthalenes, low glass transition temperature viscosity index improvers (PMA), and polymethyl methacrylate pour point depressants (PPD) to construct a composite lubricating oil system. Through the synergistic effect of the above-mentioned specific components, the following overall technical effects are achieved:

[0023] 1. Significantly improved low-temperature fluidity

[0024] While RRBO offers advantages in carbon footprint, it suffers from insufficient low-temperature fluidity. This invention addresses this issue by using auxiliary esters to reduce system viscosity and improve lubricating film formation; alkyl naphthalenes to enhance polar solubility and weaken the wax crystal network; low-Tg PMA to provide excellent low-temperature viscosity-temperature characteristics; and PPD to inhibit wax precipitation from n-alkanes. This results in CCS (-35 °C), MRV (-40 °C), and pour point performance all superior to PAO-based lubricants of the same viscosity grade.

[0025] 2. Reduce carbon footprint throughout the entire life cycle

[0026] Using RRBO as the main base oil reduces the high energy consumption and carbon emissions associated with crude oil refining and PAO synthesis. While ensuring performance, it is supplemented with low-dose, high-efficiency additives, avoiding additional carbon emissions. According to ISO 14067 life cycle assessment, under the cradle-to-grave boundary, its carbon footprint is reduced by at least 10% compared to PAO-based lubricants of the same grade.

[0027] 3. Balancing lubrication performance and stability

[0028] Alkyl naphthalenes enhance the solubility and compatibility stability of additives in RRBO, preventing precipitation; esters and low-Tg PMA synergistically improve high-temperature viscosity retention and shear resistance; at the same time, the combination of conventional antioxidants, detergents, dispersants and anti-wear agents ensures antioxidant, anti-wear and detergency properties, thereby maintaining excellent overall lubrication performance while improving low-temperature performance. Attached Figure Description

[0029] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 The figures show the DSC curves of different samples during the cooling process. As can be seen from the figures, C0 shows a significant exothermic peak at approximately -18.5 °C; the exothermic peak of sample C1 shifts to the right to approximately -20.2 °C, indicating that the low-temperature crystallization behavior is delayed; the exothermic peak of sample C2 shifts slightly to the right to approximately -19.0 °C, with limited improvement; E1 shows a broader and stronger exothermic peak at -23.8 °C, and its crystallization temperature is significantly lower than that of the control group, indicating that the crystallization initiation is further delayed. Detailed Implementation

[0031] Reference will now be made to detailed embodiments of the present invention, one or more of which are described below. Each example is provided for explanation and not for limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the invention without departing from its scope or spirit. For example, features described or illustrated as part of one embodiment may be used in another embodiment to produce further embodiments.

[0032] Unless otherwise stated, all terms used to disclose this invention (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Further guidance is provided below for a better understanding of the teachings of this invention. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0033] In this invention, unless otherwise stated, scientific and technical terms used herein have the meanings commonly understood by those skilled in the art.

[0034] The terms “containing,” “comprising,” and “including” as used in this invention are synonyms and are inclusive or open-ended, not excluding additional, uncited members, elements, or method steps.

[0035] In this invention, the numerical range represented by endpoints includes all numerical values ​​and fractions contained within that range, as well as the endpoints mentioned.

[0036] As used in this invention, the term "about" or "approximately" means within 20%, preferably within 10%, and more preferably within 5%, of a given value or range. It also includes specific numbers, such as about 20 including 20.

[0037] Furthermore, in describing representative embodiments of the invention, this specification may present the methods and / or processes of the invention as a specific sequence of steps. However, the method or process should not be limited to the specific order of the steps described herein, to the extent that the method or process does not depend on the specific order of the steps presented herein. As will be understood by those skilled in the art, other sequences of steps are also possible. Therefore, the specific order of steps presented in the specification should not be construed as a limitation of the claims. Additionally, the claims relating to the methods and / or processes of the invention should not be limited to the execution of their steps in the order they are written, and those skilled in the art will readily recognize that the sequence can be changed while still remaining within the spirit and scope of the invention.

[0038] This invention relates to concentration values, which include fluctuations within a certain range. For example, fluctuations are allowed within a corresponding precision range. For instance, 2% can fluctuate within ±0.1%. For larger values ​​or values ​​that do not require overly precise control, even greater fluctuations are permitted.

[0039] As used in this invention, unless otherwise stated, the singular forms of the articles “a,” “an,” and “the” include plural referents.

[0040] In this invention, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity of 2 or more.

[0041] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0042] The embodiments of the present invention will be described in detail below with reference to examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this invention, or follow experimental manuals or conventional conditions in the art, or other experimental methods known in the art, or follow the conditions recommended by the manufacturer.

[0043] In the specific embodiments described below, the measurement parameters involving raw material components may have slight deviations within the weighing accuracy range unless otherwise specified. Temperature and time parameters are subject to acceptable deviations due to instrument testing accuracy or operational precision.

[0044] Example 1 (a balanced approach that emphasizes simultaneous control of CCS and carbon footprint) Formula composition (by weight): Refined base oil (RRBO, API Group II regenerated chips): 70 parts Co-based base oil (C8 diacid diester): 10 parts Alkylnaphthalene: 5 parts Viscosity index improver (low Tg PMA, Tg = -25 °C, determined by DSC): 4 parts Pour point depressant (PMA type PPD): 0.2 parts Antioxidant (hindered phenol + diarylamine compound): 0.5 parts Detergent dispersant (polybutene succinimide): 2.0 parts Anti-wear agent (ZDDP): 0.5 parts Friction modifier (organo-molybdenum MoDTC): 0.2 parts Defoamer (silicone-based): 0.05 parts

[0045] Preparation method: Mix RRBO with auxiliary base oil at 50 °C, then add alkyl naphthalene, PMA, PPD and various functional additives in sequence, and stir until transparent and homogeneous.

[0046] Performance testing methods: Test methods

[0047] 1. Cold Start Simulated Viscosity (CCS) Test

[0048] The test was conducted according to the ASTM D5293 standard method. The samples were placed in a constant temperature bath and equilibrated at -35 °C for 30 minutes. The apparent viscosity was then measured using a cold-start simulator (CCS viscometer), in mPa·s. Each sample was tested in at least two parallel trials. If the relative deviation of the parallel results exceeded 5%, the test was repeated. The final result was the average value.

[0049] 2. Low-Temperature Pump Viscosity (MRV) Test

[0050] The test was conducted according to the ASTM D4684 standard method. The specimens were cooled according to the standard cooling curve and held at -40°C for 16 hours. The apparent viscosity and yield stress were determined using a miniature rotational viscometer (MRV). Results are expressed in mPa·s, and the presence or absence of yield stress in the samples was recorded.

[0051] 3. Pour point test The tests were conducted according to the ASTM D5949 standard method. The flow termination temperature was determined using an automatic pour point apparatus via optical detection under programmed cooling. Results are expressed in Celsius (°C).

[0052] 4. Product Carbon Footprint (PCF) / Life Cycle Assessment (LCA) The tests were conducted in accordance with ISO 14040 / 14044 and ISO 14067 standards.

[0053] The functional unit is set to "lubrication function to complete one specified oil change cycle";

[0054] The system boundary is cradle-to-grave, including raw material acquisition, blending and production, packaging, transportation, use, and end-of-life treatment;

[0055] Data sources include primary data from factory measurements and background data provided by ecoinvent, GaBi, or the China Carbon Emission Factor Database;

[0056] The calculation involves allocation (mass method, energy method, or economic method) and sensitivity and uncertainty analysis.

[0057] The final results are expressed in kg CO2e and compared with PAO-based lubricating oil compositions of the same viscosity grade to ensure that the functional units are consistent with the system boundary and the calculated carbon footprint reduction is no less than 10%.

[0058] The test methods used in the following embodiments are the same as those in this embodiment.

[0059] Test results: CCS (-35 °C): 4800 mPa·s MRV (-40 °C): 14,200 mPa·s Pour point: -48 °C

[0060] Compared to PAO-based oils of the same grade, the ISO 14067 lifecycle carbon footprint is reduced by approximately 12%.

[0061] Example 2 (High proportion of esters, optimal low-temperature performance, and greatest improvement in carbon footprint) Formula composition (parts by weight): Refined base oil (RRBO, API Group III regenerated chips): 65 parts Co-based base oil (C10 polyol ester): 12 parts Alkylnaphthalene: 6 parts Viscosity index improver (low Tg PMA, Tg = -22 °C): 5 parts Pour point depressant (comb copolymer PPD): 0.25 parts Antioxidant (diarylamine): 0.8 parts Detergent dispersant (boronized polybutene succinimide): 2.5 parts Anti-wear agent (organic molybdenum compound): 0.3 parts Friction modifier (fatty acid esters): 0.3 parts Defoamer (acrylate polymer): 0.1 parts Test results: CCS (-35 °C): 4600 mPa·s MRV (-40 °C): 13,800 mPa·s Pour point: -50 °C

[0062] ISO 14067 states that the carbon footprint is reduced by 15%, mainly due to RRBO replacing PAO.

[0063] Example 3 (RRBO has the highest proportion, highlighting the low-carbon advantage, and the low-temperature performance still meets the SAE J300 requirements) Formula composition (parts by weight): Refined Base Oil (RRBO): 75 parts Co-based base oil (a mixture of C8–C10 dicarboxylic acid diester and POE): 8 parts Alkylnaphthalene: 4 parts Viscosity index improver (low Tg PMA, Tg = -20 °C): 3 parts Pour point depressant (PMA type PPD): 0.15 parts Antioxidant (hindered phenol): 0.6 parts Detergent dispersant (polybutene succinimide): 1.8 parts Anti-wear agent (ZDDP): 0.6 parts Friction modifier (organic nitrogen compound): 0.2 parts Defoamer: 0.05 parts

[0064] Test results: CCS (-35 °C): 4950 mPa·s MRV (-40 °C): 14,800 mPa·s Pour point: -46 °C The ISO 14067 life cycle assessment results show that the carbon footprint is reduced by ≥10% compared to PAO-based lubricants of equal viscosity.

[0065] Experimental Example: Effects of auxiliary esters and alkyl naphthalenes on low-temperature flowability and lubrication properties Example 1 (containing 10 parts of auxiliary ester + 5 parts of alkyl naphthalene) was used as the experimental group (E1). Control groups C0 (without ester and AN), C1 (containing only auxiliary ester), and C2 (containing only AN) were set up. The amounts of RRBO+VII+PPD+functional additives were kept consistent across groups, with the only difference being the presence or absence of ester and AN. All samples were stirred at 50°C–55°C until transparent and homogeneous, and were prepared using the same raw materials and processes. Sample numbers were randomized, and the formulations were tested blindly by the testing personnel.

[0066] 1. Testing Method: 1) Low temperature fluidity: CCS, MRV, and pour point are tested in the same way as in Example 1, and viscosity and VI at 40 / 100 °C (ASTM D445 / D2270).

[0067] 2) Lubrication performance and stability: HTHS (150 °C, ASTM D4683), oxidation stability (RPVOT, ASTM D2272), anti-wear performance (four-ball wear ASTM D4172, 40 kg, 75 °C, 1200 rpm, 60 min), shear stability (ASTM D6278).

[0068] 3) Carbon footprint assessment: Same as Example 1.

[0069] 4) Mechanism characterization: DSC crystallization exothermic peak (cooling rate 10 K / min); WAT: ASTM D5773; PPD response curve: MRV was measured at the same PPD brand and dose (-40 °C). Rheological yield stress: determined by rheometer (-40 °C, shear rate scan) in conjunction with ASTM D4684.

[0070] 2. Test Results

[0071] sample auxiliary esters (parts) AN (portions) CCS -35 °C (mPa·s) MRV -40 °C (mPa·s) Pour point (°C) HTHS (mPa·s) RPVOT (min) Four-ball wear scars (mm) Shear retention rate (%) PCF relative to PAO C0 0 0 5300 16,200 -42 3.25 160 0.62 84 -8% C1 10 0 5050 15,250 -46 3.28 168 0.58 86 -9% C2 0 5 5250 16,000 -43 3.27 165 0.59 85 -9% E1 10 5 4800 14,200 -48 3.30 175 0.55 88 -12%

[0072] Mechanistic characterization data

[0073] sample DSC exothermic peak (°C) WAT (°C) Yield stress τy (Pa) D4684 Yield Stress Determination C0 -18.5 -15 105 have C1 -20.2 -18 82 have C2 -19.0 -16 95 have E1 -23.8 -21 40 none

[0074] PPD response curve (MRV -40 °C, mPa·s)

[0075] PPD addition amount C1 (esters only) C2 (AN only) E1 (ester+AN) 0% 15250 16000 14200 0.1% 14900 15700 13500 0.2% 14750 15500 12800 0.3% 14600 15400 12200

[0076] 3. Results Analysis 1) Low-temperature fluidity The reference sample C0 has a CCS of 5300 mPa·s and an MRV of 16200 mPa·s, which is insufficient to meet the low-temperature requirements of SAE J300 for 0W grade. C1 (ester only) shows some improvement: CCS decreases to 5050 mPa·s, MRV decreases to 15250 mPa·s, and the pour point drops to -46 °C. This indicates that low-viscosity esters can directly dilute viscosity and lower glass transition temperature. C2 (AN only) shows limited improvement: CCS and MRV are almost close to C0, with only a slight decrease in pour point to -43 °C, indicating that alkyl naphthalene alone does not contribute much to low-temperature fluidity.

[0077] E1 (ester + AN) showed significantly improved low-temperature performance: CCS decreased to 4800 mPa·s, MRV decreased to 14200 mPa·s, and the pour point further decreased to -48 °C. This improvement was significantly greater than the simple superposition of C1 and C2, indicating a synergistic effect between the ester and AN.

[0078] 2) Lubrication performance and stability All HTHS values ​​remained within the range of 3.25–3.30 mPa·s, and E1 did not show any weakening of the oil film at high temperatures. RPVOT showed an oxidation resistance time of 175 min for E1, higher than CO's 160 min, indicating that the combined use of ester and AN did not reduce system stability but instead delayed oxidation. In the four-ball wear test, the wear scar diameter of E1 was 0.55 mm, better than CO's 0.62 mm, indicating improved anti-wear performance. Regarding shear retention, E1 reached 88%, significantly better than CO's 84%. These experimental results demonstrate that the improved low-temperature performance did not come at the expense of lubrication performance and stability.

[0079] 3) Carbon footprint Based on the ISO 14067 life cycle assessment, the PCF of E1 is reduced by approximately 12% compared to PAO-based compositions of the same viscosity grade, meeting the requirement of "≥10%".

[0080] 4) Mechanism characterization The DSC exothermic peak of E1 and WAT are significantly shifted to the right by 3°C to 5°C, indicating that the wax crystals are finer and the network has disappeared. Figure 1 The yield stress decreased from 105 Pa for C0 to 40 Pa for E1, and D4684 showed no yield stress, proving that the wax crystal network was completely destroyed. The PPD response curves showed that, at the same dosage, the MRV decrease slope of E1 was much greater than that of C1 / C2, proving that the PPD effect was amplified in the "ester + AN" system.

[0081] 4. Conclusion Experimental results show that auxiliary esters, when used alone, can improve the low-temperature performance of RRBO-based lubricants, while alkyl naphthalenes, when used alone, contribute little to low-temperature fluidity. Notably, when both are used simultaneously, not only are CCS, MRV, and pour point significantly better than the groups added alone, but the improvement exceeds the simple sum of their individual effects, demonstrating a significant synergistic effect between the auxiliary esters and alkyl naphthalenes. This synergistic effect enables RRBO-based lubricants to achieve fluidity at -35 °C and -40 °C that reaches or exceeds that of PAO-based lubricants, while maintaining excellent oxidation resistance, anti-wear properties, and shear stability, and achieving a significant reduction in carbon footprint.

[0082] From a mechanistic perspective, RRBO contains a significant amount of n-alkanes and trace amounts of residual wax, which readily form a crystalline network at low temperatures, leading to a sharp increase in viscosity. When low-viscosity esters are added alone, their low glass transition temperature and strong molecular polarity dilute the system viscosity and partially dissolve wax molecules, thus lowering the crystallization initiation temperature (the exothermic peak of DSC and the WAT shift to the right), but the crystalline network is not completely destroyed. When alkylnaphthalenes are added alone, their aromatic structure improves the system's solubility parameters and disperses some wax crystals, but because the overall viscosity is not significantly reduced, the improvement in MRV and CCS is limited. Only when esters and alkylnaphthalenes are present simultaneously do their effects amplify each other: esters lower the base oil viscosity and crystallization barrier, making wax crystals more easily interfered with and dispersed by alkylnaphthalenes; alkylnaphthalenes improve the dissolution environment of additives and ester molecules, enhancing the crystallization-modifying effect of PPD. The overall results show that the E1 sample exhibits a significant rightward shift of the crystallization peak in DSC / WAT, a yield stress less than half that of the control, and no yielding phenomenon in MRV. Simultaneously, the slope of the PPD response curve is significantly increased, far exceeding the additive effect of either component acting alone. These mechanistic data collectively indicate that the effects of the auxiliary ester and alkyl naphthalene in RRBO are not simply additive, but rather form a non-obvious synergistic mechanism, thereby significantly improving low-temperature fluidity while ensuring lubrication stability.

[0083] In summary, the present invention achieves the technical effect of balancing low-temperature performance and low carbon footprint, while also taking into account lubrication performance and stability.

[0084] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A carbon footprint-quantified lubricating oil composition, comprising, by weight: The mixture contains 60-75 parts of refined base oil, 8-15 parts of auxiliary base oil, 4-8 parts of alkyl naphthalene, 3-6 parts of viscosity index improver, and 0.12-0.30 parts of polymethyl methacrylate pour point depressant. The viscosity index improver is selected from polymethyl methacrylate with a glass transition temperature not higher than -20 °C, and the auxiliary base oil is a diester of a dicarboxylic acid and / or a polyol ester with a carbon chain length of C8 to C10.

2. The carbon footprint quantified lubricating oil composition according to claim 1, wherein the auxiliary base oil has a kinematic viscosity of less than 10 mm² / s at 40°C and a pour point not higher than -40°C.

3. The carbon footprint quantified lubricating oil composition according to claim 1, further comprising 0.3 to 1.0 parts of an antioxidant selected from hindered phenols, diaryl amines, and mixtures thereof.

4. The carbon footprint quantified lubricating oil composition according to claim 1, further comprising 1.5 to 3.0 parts of a detergent-dispersant, said detergent-dispersant being polybutene succinimide or a derivative thereof.

5. The carbon footprint quantified lubricating oil composition according to claim 1, further comprising 0.2 to 0.8 parts of an anti-wear agent, said anti-wear agent being zinc dialkyl dithiophosphate and / or an organic molybdenum compound.

6. The carbon footprint quantified lubricating oil composition according to claim 1, further comprising 0.1 to 0.6 parts of a friction modifier selected from fatty acid esters, nitrogen-containing organic compounds and / or molybdenum disulfide derivatives.

7. The carbon footprint quantified lubricating oil composition according to claim 1, further comprising 0.01 to 0.2 parts of an antifoaming agent selected from silicone or acrylate polymers.

8. The carbon footprint quantified lubricating oil composition according to any one of claims 1 to 7, wherein the CCS viscosity at -35 °C is not greater than 5000 mPa·s, and the carbon footprint is reduced by ≥10% compared with a PAO-based composition of the same viscosity grade under ISO 14067 life cycle assessment.

9. A method for preparing the carbon footprint quantified lubricating oil composition according to any one of claims 1 to 8, comprising: (a) Mixing the refined base oil with the auxiliary base oil; (b) Under stirring conditions, the other components are added sequentially; (c) Heat and stir until the additives are fully dissolved to obtain a uniform and transparent lubricating oil composition.

10. The method according to claim 9, wherein the heating is performed by controlling the mixing temperature to be 45°C to 60°C.

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