Originally Posted By: Ken2
Nothing can render the entire warranty void. If you do anything that causes damage to a part of your car, the car maker will not pay to repair that part.
You do not have to follow any of the recommendations. But, if a part fails, you might be on the spot to prove that it wasn't the result of anything you did or failed to do. Now it gets sticky, and you don't want the car maker stonewalling paying for the repair--you want your car back. All that said, if the transmission fluid is red, they won't know if you used an unapproved ATF (like Amsoil, Redline, many others). If the engine oil and filter come out reasonably clean, they likely won't question you. If the oil has to be chiseled out of the engine, and if the filter is a solid cylinder of coal...keep your checkbook handy.
ATF can be tested to see if the wrong stuff is used. Oil analysis will show if the additives match the OE fluid. At the same time, Flashpoint is unlikely to rise because there would be no fuel/oil dilution, so the flashpoint of OEM fluid could be tested against OEM fluid. Allison transmission added an extra step by having ATF that can be tested by light.