The invention discloses a high-pressure oil passage by-pass 
economizer of a diesel-powered car, comprising a circuit 
control switch, a high-pressure oil passage by-pass one-way valve, an oil return cylinder, an air cylinder and an 
electromagnetic valve. The circuit 
control switch and the 
electromagnetic valve that is connected with an 
air compressor can automatically select an air 
throttle or set a speed and even set whether the 
electromagnetic valve operate or not under a 
throttle normally closed condition; the electromagnetic valve is connected with the air cylinder to drive the oil return cylinder connected to the air cylinder; two to six the 
high pressure oil passage by-pass one-way valves corresponding to 
skew notches on a push rod are arranged on one side of an oil cylinder sleeve at intervals; the 
high pressure oil passage by-pass one-way valves are serially connected between a 
high pressure oil 
pipe and an oil 
injector via a three-way high pressure oil 
pipe connector; when the push rod is pushed to eject a stepped spool, the high pressure diesel is released through a stepped hole to the oil cylinder and flows back to the 
oil tank, indirectly blocking 
oil supply to a deactivation cylinder of an engine; when the push rod in the oil return cylinder returns back, then the stepped spool is restored, the oil return is turned off, and the 
oil supply to the engine of the car is recovered. The invention has advantages of low cost, high degree of 
automation, safety, reliability, significant oil economization effect and the like, and is specially suitable for diesel-powered cars.