SamWind

Just bought 1999 Chevy Express 1500 conversion van with 68,000 miles.


I'm switching engine oil to Royal Purple HPS and would like to also use Royal Purple ATF in the transmission. Royal Purple website says its ATF is compatible with Dexron III F, G or H. My manual recommends Dexron III but has no letters (like F, G or H). GM dealers now use Dexron VI, which is backward compatible with Dexron III, but Royal Purple website says its ATF is NOT compatible with Dexron VI. So my question is whether there is any way to tell whether my previous owner(s) ever used Dexron VI, ie, whether there is any Dexron VI in my transmission. My transmission fluid is as pink and clear as the day it left the factory. If I can't use the Royal Purple ATF I'm switching to Mobil's synthetic ATF, which my Chevy dealer says will not be a problem,


TIA


Sam

greenfire

Do they mean not compatible with fluid that may still be in your system or not compatible with cars that require it?


If its the later then I say your fine...

SamWind

Royal Purple says mixing causes no problems, but you should not mix the RP HPS with Dexron VI while the car is still under warranty because the HPS has wear reducing elements which the government does not like, because of the potential to damage the catalytic converter. This potential is very low, in my opinion, because the only way the oil can get into the catalytic converter in the first place is by blowing past the rings, and if that is going on what happens to the catalytic converter is probably the least of your worries.


There are a few places on the internet that warn of leaks following switching to Royal Purple, but I'm going to do it anyway, because I'm looking for better mpg. I have a 1999 Express 1500 conversion van with only 68,000 miles that runs and shifts fine and has no leaks. If I learn that I shouldn't have done that I'll post that on here.

greenfire

I can't see how transmission fluid would damage your catalytic converter, unless I'm missing something here.

SamWind

Brain fart on my part. It's the RP engine lubricant that has the substances that MIGHT damage the cat comverter. The RP AT fluid's drawback is that it's use will void the warranty in cars that require Dexton VI or the more recent Mercons. RP says it won't hurt anything but point out the void warranty problem.