Haha, an almost 30 year old Toyota Minivan on Full Synthetic race oil.
Some of criticized me for running full synthetic everywhere on this van. I have Amsoil Signature Series ATF and Severe Gear 80W-90. I don’t drive easy on my vehicles, but another factor that plays a rather important role is the fluid capacity.
I think of it this way, Toyota engineered the vehicle to handle the specific use case that it was intended for. In 1992 the Federal speed limit was capped at 55 mph. Therefore, all the fluid capacity designs seemingly followed suit. The rear differential on this van is only 1.6 quarts! While Tacomas rear ends nowadays run in the neighborhood of 3 quarts. The 4-speed automatic transmission (Model: A46DE) has a paltry 6 quarts TOTAL capacity! Toyota 4Runners/Tacomas transmissions have approximately 12+ quarts! So to say the least, I am deficient with fluid capacity to handle heat.
I have since installed a transmission cooler with an electric fan. It has kept temperatures at bay. Running today with the readings I found of 270F on the engine oil, I measured 197F on the transmission pan. From what I gather this is relatively safe operating temperature for the ATF, especially since it’s full synthetic.
As for the differential, it read 235F today. Which is on the high side, but well within Amsoil Severe Gear’s capability to handle.
The odd part is that the engine oil is the last thing I thought would overheat because of capacity. It has a healthy 6 quart capacity for its 2.4 liter displacement. So it’s odd to me that it’s heating up to 270F.
I do this drive, 80+ mph, every afternoon going home. I live in the Southeast and anticipate 90+ degree F weather for July, August, and possibly part of September. I’m running 5,000 mile OCIs, but I’m considering cutting this one short and sending off the oil for analysis. Then replacing the Pennzoil Platinum High Mileage with Amsoil Signature Series 5W-30 and just run Amsoil in the hotter months. I do not plan on changing my driving habits, so I guess there’s little choice I have.
I would run Amsoil exclusively, but I just cannot afford it on 5,000 mile OCI. I don’t feel comfortable with extended OCIs, so I can see myself running half Amsoil Signature Series and then half Pennzoil Platinum High Mileage during the year.