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Do I need an oil cooler if towing with a 4 cyl. Highlander?

I recently purchased a new 2012 Toyota Highlander with the 4 cyl. engine. This model did not come with the tow package, and I tow an aluminum trailer with 2 Harleys on it each year approx. 3,000 miles. I’ve gotten several conflicting opinions and wanted to get a consensus if I should have an aftermarket oil cooler installed-

You don’t want an oil cooler but instead a transmission fluid cooler. This is a small radiator installed in series with the regular tranny fluid cooler. This prevents the transmission fluid from getting too hot when towing with the vehicle. And is one of the components included when ordering the vehicle with the towing package.


Yes you should. You can never have a to cool trans when towing. Also you should make sure you change the trans fluid about every 25-30000 miles. This means the fillter too and not a flush job. You should have got the tow package.

Your vehicle may have come with an auxiliary transmission oil cooler. Look through the bumper opening below the left headlight, this is where the factory aux. cooler is located.

What does your owners manual say? 2000 pounds is a lot for a 4 cyl Highlander.

You will find that what you really need is 6 cylinders…

A transmission fluid cooler is a great option even if you’re not towing. A look at the options list shows the auxiliary trans fluid cooler is part of the Tow Prep Package which do not have and will be pricy to get.

Personally, I’d leave the Toyota at home and ride the Harley.

OK- the weight is approx. 2400 lbs. so I’m within the specs.- What I’m seeing is I need a trans cooler, not a oil cooler?

I don’t have an aux. tranny cooler, but the tranny fluid is piped into the bottom of the radiator-

And there in the lies the problem.

When you tow with a vehicle the cooling system has to keep both the engine coolant AND the transmission fluid cooled. Without an auxilary transmission cooler the transmission can operate at a higher temperature when towing. This then breaks down the transmisson fluid, which then causes the transmission to run hotter, which then breaks down the transmission fluid, etc…

If you’re going tow with the vehicle, install an auxilary tranny cooler.


Yes, I would put one on before I towed anything. I actually avoioded towing with my Suburban because of the transmission problems that other Tahoe/Suburban owners were having.

The FACTORY towing package is BY FAR the best solution…You get everything you need properly designed and installed…

I agree that the factory package is the best option. However, adding it on now might get very pricy.
Toyota lists a Tow Package and also a Tow Prep Package. Other than the hitch, wiring, and so on they also show upgraded brakes, heavy duty alternator, heavy duty cooling system, aux. trans cooler, and a few other things.
The thought of walking into a dealer and asking for all of that stuff to be added on would make me cringe. Lord only knows what the price of an across the counter Toyota HD alternator is.

At a bare minimum, the vehicle should get a transmission fluid cooler. Those are a great idea even if no towing is done.

Guess I’m reading the wrong info. You DONOT appear to be operating within specs. Without the tow prep package, the tow weight is 1500 lbs and with it, it jumps to 3500 lbs. You are operating over on one end and near the limit on the other. Just as important is the combine vehicle weight of both tow and capacity. I bet you are over that as well when you tow with gear inside. Expect problems sometime regardless of what you do. But, I would tend to agree with everyone on full factory equipment as you have a unibody which has a more specialized hitch. You are towing on the edge.

Even with the v6, the standard tow is 2000 lbs. Your car needs help ! You may just find, that it’s LESS expensive to trade at a Toyota dealer now for 2012 V6 Highlander with package or a 4Runner which is made for it. They may even have some 2012 s on the lot. Or Toyota dealer always has year or two only off lease cars of all types. A used Pilot can give you 5 k tow and a Ridgeline the same if you don’t want to go truck.

CORRECTION: My Alumi Lite trailer weighs only 360 lbs., so with both bikes loaded, the total weight is 1600 lbs.- Two mechanics I spoke with told me not to sweat it as I only tow one trip (2400 miles) a year from (Florida to NY)- Just change the tranny fluid at 30,000- I see there is a combo tranny/oil cooler setup on the market as well- Any additional thoughts/advise appreciated.

Around here…many of the companies that sell or rent trailers can sell and install towing packages for almost any truck. This includes trans-cooler, trailer brake wiring, upgraded alternator, trailer hitch, load leveling trailer hitch, wiring system…Should be cheaper the dealer…but still not cheap.

But in this case the only thing I think you need is trans cooler, wiring and trailer brake system if the trailer has brakes.

Mike offers good minimal suggestions that you should consider. Just one trip is good but 2400 miles will tax the transmisdion. IMO, the motor is the least of your worries. Go for the cooler then. If it is awd, you have a definite handling advantage. If you don’t , drive carefully and be safe.

OK- the weight is approx. 2400 lbs. so I’m within the specs.- What I’m seeing is I need a trans cooler, not a oil cooler?

Think again, you’re actually grossly exceeding the rated trailer weight limit by 900 pounds per the owners manual.
Without the factory tow package, the 4 cylinder 2010 Highlander is rated to tow 1500 pounds.

FoDaddy- I corrected the total weight to 1600 lbs.- A mechanic at the Toyota dealership me not to worry about it- the trans. oil is already routed through the radiator… just do a trans. service at 30,000 miles- I’m towing once a year, flat terrain- The mechanic at U-Haul who installs after market coolers said the same thing- I realize everyone has an opinion!

We used to own a motorhome on a Ford chassis that had a transmission line through the lower radiator tank and it also had a small auxiliary radiator in the same circuit. I never checked but I suspect that the auxiliary radiator was downstream from the lower radiator tank trans fluid line. Otherwise the engine coolant would simply reheat the cooled trans fluid. If you are doing most of your towing in cold weather, that would lessen the need for an auxiliary trans cooler.