Switch to Synthetic AT Fluid for Towing?

[Brent R]

Has anyone switched to synthetic automatic transmission fluid to reduce heat and wear while towing?

We will soon be towing an Escape 21 with our 2011 4Runner, and although the SUV has a factory AT fluid cooler, I'm still concerned about heat buildup, especially in summer weather on steep grades.

I'm also concerned about wear on components because the trailer will weigh about 4300 pounds, ready to camp, pretty close to the 4Runner's rated tow capacity of 5000 pounds. That might give the transmission quite a workout, even if I stay out of overdrive and shift manually to prevent the AT from "searching" for gears.

I look forward to hearing about anyone's experience while towing with any vehicle using synthetic AT fluid. Thanks!

[J.R.]

I would ask the engineers at the factory, NOT the dealership or its mechanics. I don't trust them. Example: A mechanic for a local dealer told me to use nothing but 30W oil in my engine, then at 50,000 miles switch to 40W. The engine was engineered to use only 5W-30 for the entire life. So ask this question: Who knows best? The mechanic or the people who designed and engineered the product?

[Roy in TO]

Trick question there J.R.

The answer could have multiple variables. Your oil example might give a spec for North America where some of us have a much colder winters than Texas and a multigrade oil is easier to safely spec out in an national level.

The local mechanic may have seen the end results of the designers and engineers. For example my Ranger has a Rear ABS valve that continues to fail. Ford stopped making replacements and the remanufactured ones will only hold up to a sole hard braking maneuver. After replacing 3 RABS valves at $175 a pop in parts alone my mechanic suggests I just leave it and drive the truck with standard brakes knowing that the rear ABS does not work. (front brakes are non ABS)

OTOH I would trust the designer and engineers when it comes to tow limits.

[SilverGhost]

I would stick with the recommended fluid unless there is a large following of Toyota owners that had found a weak spot and a better fluid. There are some good and bad additives that help with heat transfer, also. If you plan on trips to or through hot areas like Phoenix in summer, then an additional ATF cooler would be a safety margin. Just a note - the factory cooler actually WARMS the cold ATF up to lower emissions and raise MPG, when the car is cold. I would suggest a cooler with a thermostat.

Best advise is to keep doing what you do for the hills (out of OD, prevent hunting). But the biggest heat buildup in a auto transmission is the shear forces on the oil inside the torque converter. If you can keep the lock up clutch engaged more of the time it help a lot. I would research when the lockup clutch is active (in OD and/or direct) and try to keep the trans there. Some older OD automatics only locked up in OD, but most newer ones lock up almost all the time. And all have different strategies when the temperature gets too high.

Jason

[NEWFISHER]

Working for GM for 20 years, this is my opinion. Manufacturers don't live in the mountains of the Northwest. The recommendations for Ohio, Detroit etc are much different than Texas, Florida, NewMexico, California etc.
Toyota automatics are pretty bullit proof in the trucks and 4runners and if towing within the recommended range, generally do not have issues. HEAT is the biggest killer of automatics,having the factory cooler is good and adding a second air to oil would be better.
Synthetic are great when you use them after the component is just past its break in period. I have seen complications switching to syn fluids on high mile components. I have seen syn fluids used just after break in on components that have been torn down with 300,000 and look new. I run syn fluids in everything I own except the older flat tappet engines in my classics. They have syn trans , powersteering and rear diff fluids. The newer rigs all run Mobile 1 including the motorcycles.
Stop by your local engine rebuilder, transmission shop and rear diff grear guy and ask to look at cores that were known to run synthetics, ask how many miles were on them then make your descision.

[Laura & Rick]

Brent, I believe that your 4Runner uses WS (World Standard) transmission fluid. If so, it's better to stay with WS than go to another type of fluid.

[sokhapkin]

I invested to scangauge II device and monitor the TF (transmission fluid) temperature. That's the best way rather than guess.

The TF temperature on my 2001 Mercury Grand Marquis with factory TF radiator stays in 175-185F range. 185 is reached if I turn off overdrive(!) when towing. With overdrive on the temperature rarely reach 180. Go figure... Usual advice is "turn overdrive off when towing"...

[MC1]

In our TV, an Infiniti G35, synthetic tranny fluid is factory standard (Jatco transmission). I also changed the rear end fluid to Synthetic and have used Mobil 1 10w/30 oil in the engine. All have worked great for 12 years now.

Note: Generally speaking synthetic is a better product than dino and as long as you can get the OK from an authority on your vehicle it is a good thing, especially when towing.

[J.R.]

Perhaps I should have mentioned that this mechanic makes those recommendations for customers world-wide including Alaska, the desert southwest and Texas. There is not a single oil weight for all conditions and I too use only Mobile 1 with more than a half million miles of driving without any problems.

Originally Posted by Roy in TO

Trick question there J.R.

The answer could have multiple variables. Your oil example might give a spec for North America where some of us have a much colder winters than Texas and a multigrade oil is easier to safely spec out in an national level.

The local mechanic may have seen the end results of the designers and engineers. For example my Ranger has a Rear ABS valve that continues to fail. Ford stopped making replacements and the remanufactured ones will only hold up to a sole hard braking maneuver. After replacing 3 RABS valves at $175 a pop in parts alone my mechanic suggests I just leave it and drive the truck with standard brakes knowing that the rear ABS does not work. (front brakes are non ABS)

OTOH I would trust the designer and engineers when it comes to tow limits.

[Darwin Maring]

Purchase a Costco Extended Warranty for the tow vehicle and use the factory recommended fluid and then don't worry about it. The Costco Warranty is Golden.

[thombiz]

I'm not sure if the '11 4Runner has WS (World Standard) transmission fluid or not, but I'm just about positive it does. The WS transmission fluid Toyota uses is a synthetic. I had an 2001 Tundra which had standard transmission fluid in it until the first flush when I put it Mobil 1 synthetic transmission fluid. Every flush thereafter was with Mobil 1. I towed a '97 Airstream Excella 25 about 150,000 miles with that truck and never had a tranny problem. When I sold it at 189,000 miles the tranny still shifted and operated like new.

[Bob Miller]

A little late for the OP but, if you are depending on the oil cooler that's on the radiator tank, you will never get transmission temps below what's in the bottom of the radiator tank, usually close to engine temp.

On Toyota automatic transmissions used in mini-motorhomes, it was always recommended that an extra oil cooler be added in front of the radiator. In 1987-88 A43D equipped Cab & Chassis, one was factory installed.