Eric the Car guy has an interesting post on this. Essentially, he says that synthetic oil can find leaks due to the fact that it flows better than conventional. To answer your question, no, it won't harm your engine, but it might find leaks that conventional will not. If conventional is working for ...

I am posting this to help anyone else who struggles with a P0171 or P0174 lean condition code. My car is a 2003 S40. My symptoms included: 1) CEL code p0171 and p0174 2) Stall at acceleration after a stop and also stall after letting off the accelerator at low speeds 3) Hesitation at wide open throt...