I have a transmission service now due. My car is a '90 Majestic that just turned 100K miles, the last trans service was 30-40k miles ago and I am seriously considering swapping to Mobil 1 synthetic. Any thought on changing to synthetic at 100K miles? To be sure synthetic may have been used in the past.

Thank you all,
Roger

 

Hi Roger,

Mobil 1 ATF is reportedly good in the ZF 4HP24 transmission, but it would be my second choice behind Redline Oil D4 ATF, which is also fully-synthetic. The reason is that the fluids originally specified were Dexron II or Dexron III, which had a viscosity index of 190. The vi of Mobil 1 ATF is 176, while the vi of Redline Oil D4 ATF is 198.

For years I ran Dexron VI ("six") in our '93 with the same transmission as in your car, not realizing that due to the lower vi of Dexron VI (just 145), the torque converter was never fully locking up. When I changed to Redline Oil D4 ATF, the difference was night and day. Gearshifts were just as smooth, but now acceleration was more "hooked up," we had real engine braking while descending hills, and the difference between Normal and Sport modes was now amazing, with the transmission holding lower gears coming out of curves to much greater effect.

The only issue is that you can't buy Redline Oil D4 at Walmart or most local auto parts stores, but if you order it from Summit Racing, shipping is free on orders over $99, and two 5-quart jugs of D4 will come close to that. Just add a small tool like a Titan non-marring lug nut socket for your Jag and you're there.

Cheers,

Don

 

Thanks Don, I will keep your recomendation in mind.

 

I commented on the wrong thread. Never mind.