That's a myth! There is no problem mixing brands, API service categories, or synthetic and mineral base stocks.

A few years ago while reading the accident reports in the back of Flying magazine, I came across an inflight engine failure. Inspection of the engine revealed that an oil passage was clogged with PFTE ("teflon"). The clogging occurred at the intersection of two passages, gun drilled normal to each other. Fluid currents had caused the PFTE to pile up in the corner finally restricting the passage to the point where a bearing seized due to lack of adequate oil flow.

I made some inquiries, but was unable to find any FAA directives on the use of PFTE.

PFTE is a stringy solid. The strings are too small to be trapped by the filter, but they can clog small passages. Bottom line is that PFTE is pure snake oil as an engine oil additive and should be avoided!!!

As far as what oil to use in your car - look at your owners manual! Buy the required API spec or the latest iteration (currently SL for spark igntion engines) in a viscosity range that is suitable for the range of temperatures that your car will see on cold starts for the period the oil will be in the engine. Brand name is unimportant other than your faith that the brand is actually blended to meet the API spec. I am relatively confident that name brand oils are properly blended, and that probably applies to house brands too, so the issue comes down to price.

Duke