I would NEVER use mercon V fluid in my c4, not unless it has been rebuilt, as mixing the fluids is a big concern as well. Here's a simple chart, from a manufacturer that shows what Mercon V is compatable with http://www.valvoline.com/pdf/MERCON_V.pdf as you can see it is completely backward compatable, with the exception of type F fluid. and here is the type f.... for type f ONLY scenarios http://www.valvoline.com/pdf/Automatic_Transmission_Type_FA.pdf Type F among other things, has a stronger resistance to foaming, and has a more agressive detergent package, in an oil base that has more adhesion properties than the Mercon V fluid... what that means to you? it better sticks and lubricates the transmissions designed for it, as well as provides proper heat transfer rates via your transmission cooler, and keeps the debris and clutch dust from building up inside the transmission. This nonsense of using Mercon V in an old C4, leave it to the mustang guys who don't mind rebuilding their trans every couple of years.
I rebuilt my c4 five years ago, I have since used Dexron II because here nobody sell Type F, but i need a better oil for my c4 and my power steering, I can find DII DIII and Mercon V only
I had my transmission rebuilt 3 Years age. Although it is not a daily driver. The guy that built it for me said to use mercon v. He builds transmissions for Drag cars, pulling truck, rock crawlers etc. He guarented it as long as I own the car. I have never had a problem with it over heating the transmission. So i guess it would work.
