Interesting discussion boys. I would consider the major problem with most vehicles towing today is the "cooling" of trans fluid through the radiator. Worked hard engines will over heat a radiator as will a worked hard torque converter. One cooler two jobs?

In my Y62 Patrol the A/T does not run through the radiator but has a separate cooler sitting in front of the radiator and aircon rad. To enable quick warm up of A/T ,the fluid is pumped through a plate heater.

I change the full synthetic fluid every 10k. The ATM of van is 2700 (sometimes more) and fluid darkens a little which is usual but certainly still serviceable.

Every other Patrol I have owned I have bypassed the radiator and fitted a large cooler. I have always fitted a temperature gauge to the A/T oil pan too but have not had to worry with this model.

hi
The internal cooler in the radiator is not big enough , it brings the trans oil upto operating temp then keeps it there. It will never transmit enough heat to cause overheating of the engine even thou its a very efficient fluid to fluid type . Its to small .
Many makers when towbar was specified offered an additional cooler . IT was run in series with the rad internal cooler. The factory add on coolers were mostly to small also .

It does not help when using a factory style in rad cooler that engines must be run at 100-105 cel . The trans will then have no choice but to run at a high level also .

Yep a heat exchanger, liquid to air, or liquid to liquid, must have temperature differential or else it won't work. Simple !

hi
Operating temp of engine is +/- 95 deg cel so this only gives u 5 deg to play with . From experience u will get that rise from a loaded 8x 5 trailer .
Fit for purpose NOT.

Synthetic engine oils definition has been watered down . If its 100% manmade its synthetic not the imposters /fake wanna bees . Try both types there is a big difference . The difference was argued in court Mobil vs Castrol . Unfortunately Castrol won . This was not a benefit to consumers it was to benefit Castrol`s bank balance . The customer lost that day .

Engineered oil will last way longer than mineral easily . But in a racing environment is still contaminated easily . The excessive heat also degrades just not as fast as mineral . Oil still needs to be changed regularly .

A radiator in a passenger car will not overheat with cooler in front of it .

I think the conspiracy is when dealers etc charge big money to fit them . A little like oil seperaters . I can fit a good cooler for $300 . But the prices I have seen by franchise companies is atrocious!! What Ive found on some models ? Just an extra pipe across the front is used to cool hydraulic fluid . My WRX Subaru does that for power steering .