2 things;

I just read that once you put synthetic oil in your car, you can never switch back to regular? Is this true? And why...

What would happen if a quart of different oil was added to oil in the engine? (Synthetic+Regular or vice versa)

Thanks.

 

You can switch back and forth between regular and synthetic. There is no harm in mixing regular with synthetic.... that's actually what those oils called "Part Synthetic" or "Synthetic Blends" are... a mix of regular and synthetic oil.

For example:

 

Once you run synthetic is recommended to stick with synthetic. AMSOIL all duh way!

Has anyone used the ATF from AMSOIL in a G35?