I've heard quite a bit about oil coolers. How they're supposed to make your oil last longer, protect better, etc. I have some concerns, which I hope can be addressed. This goes for transmission coolers as well as engine oil coolers.

First, wouldn't cooling the oil too much cause the water to not get boiled out? Seems to me you should get it to at least boiling point (212F) to boil the condensation out. Same goes for fuel dilution. Dont you want to get it good and hot to boil off the excess fuel, should there be any?

Next, is additives. I've heard that certain anti-wear additives dont work until a certain temperature. Wouldn't cooling the oil too much cause the additives to not function correctly?

Maybe I'm just paranoid, and the oil coolers dont cool it enough to make a difference. Am I on to something here?

 

Actually, a sustained oil temperature of 180F is sufficient to evaporate moisture. Most engines dont need an additional cooler unless towing, etc. GM includes an engine oil cooler in tow packages. The automatic transmission on the other hand is much more temperature sensitive and, generally, the cooler the better.

Jim

 

First, oil coolers are usually used with auto trannies, and in most cases they are used because of towing/heavy load. Someone posted that for trannies, the optimal oil temperature is 170F, and overcooling will slightly degrade the performance of the tranny, but otherwise do no harm. However, overheating can quickly destroy a tranny, so it's safer to err on the cooler side. I don't remember the exact numbers,
(probably around 220 - 250F) but if your tranny oil gets hot enough, you better take a break.

As for engine oil coolers -- engines usually have a dedicated cooling system that removes excess heat, and engine oil is I think a lot more resistant to heat. As for low temperatures; locally, the engine oil can be a lot hotter than what you could measure with a gauge. Imagine a thin film of oil on the cylinder wall -- it's usually a lot hotter than the oil in the crank case.

 

Yeah you can over cool and engine and a little bit the same on a tranny.

The engine really wants to run 180 to something like 200 depending o n the engine. The guys who put in 160 thermostats and a big honking oil cooler and who just do normal driving especially in cold weather will find that they get more water condensation and contamination. Running at 180+ "burns off" many of the contaminants in oil. If you leave the contamination in, over the long haul you will decrease the life of your engine. It takes a long time usually for the damage to be apparent, that is why some people think cooler is better on engines, they don't know til too late.

As for trannys, a tranny shop guy and several magazine articles said that the main problem is overheating, but you can over cool too. Overheating will always cause damage over time. I think there is some chart going around that says every 10degrees over 240 cuts tranny fluid life by half. So you do want to stay under say 200 or so. I like 180 or less my self. My 94 F250 E4OD 4x4 runs somewhere around 150 to 180 with no trailer on hot suimmer days after a few hours of freeway speed.

BUT, if you run too cold, let's say you don't tow and you drive in freezing conditions, your atf may never or take a really long time to get to operating temps. I haven't heard of outright damage from this, but the tranny doesn't shift as efficiently and you will loose gas mileage due to delayed shifts. My truck delays shifts something like 500 RPM until the temp gets up a bit. My tranny on near freezing days may never get past 110-130 on long drives without a tow. It will take several miles at freeway speed before my tranny shifts at it's normal warm shift points. This is true of my 4 most recent vehicles, 3 of which I still own.

If you do get a cooler, the tranny shop advised me to get the size just bigger than your greatest expected combined weight. For example if my truck GVWR is 9,000(I forget) and my trailer GVWR is also 9,000, then I should get a cooler that adds on to my stock capacity for a total somewhere around 20,000#s at most. Don't go for the 40,000# cooler. It is at best a waste of money and might cause lost mileage, and with our trucks every bit counts. In extreme cold may it can cause damage, but like I said, haven't seen any serious discussion of that possibility.

The tranny shop I used once due to my stupidity with my truck said the factroy aux cooler on my model was sufficient for my trailer load. I tend to think he is right most of the time but I have seen spikes of 220 once in a great while under heavy heat load, long dirves with headwind. With my truck I might go up one size or add a small extra aux cooler, but that means 2 more fittings that could leak or fail.

Just my opinion based upon paying 3 good shops too much money for my mistakes over the past 30 years.

Jim Henderson

 

what is available for coolers on the 5 speed man. trans.? These use atf and can get hot towing.

 

Never seen coolers for manuals, and I'm not sure if manual trannies have the openings for oil lines to add an aftermarket cooler. If you think your manual is overheating (which I kinda doubt) you can use a regular motor oil (preferably synthetic with lots of moly), you just need to find the right weight for your tranny. I'd start with 10W30, and go up/down based on feel and noise.

 

JIM, How is this idea, what do you think? Your ideas and experience all make perfect sense. I was thinking, if you are running a oil or trans cooler, in freezing temperatures, why not partially block the radiator, or fins in the cooler, with cardboard, or similar device? This would block the flow of frigid wind chill temps, allowing the fluids to warm up more in these conditions? When towing, or warm weather arrives, the airflow blockage can quickly be removed. Just a thought.... ED

 

If one is really concerned about over cooling, why not run a valve with a bypass hose. You could bypass the cooler when not needed, and use it when needed.
Dan

 

Manual trannies do not heat up the oil very much because there is no torque converter, the main source of heat in an automatic.

Jim

 

Keep in mind I am not a pro or anything like that. I just like to tinker and have driven in 120+ and down into the low teens. Based on that experience and what I have read and heard from paid professionals, most of us don't need an engine oil cooler, but many of us could use a properly sized ATF cooler.

That said, ever notice the louvers on the grill of some of the big trucks? Some use kind of a bra. Same idea for cold weather. Cut off the airflow some. Some other people use a cutoff valve. I worry about too many extra connections, because ATF and oil finds leaks and more connections give it more chances.

I did once run a 160 thermostat in a riceburner and nearly froze to death in a snow storm. We put some blocks infront of the heater but a lot of cooling air gets thru underneath I think.

Use good oil rated for your temperature and change regularly. That probably does more for most of us than going to a cooler. Use an engine oil cooler only if you really need one, like cops and taxis which idle a lot. Also some others use the coolers for towing.

I have a 94 F250 460 that I use to tow. The oil is syn and the water temps have never gotten much past half way even in 105+ heat thru a forest fire uphill towing my 8,000# trailer. Ther tranny could use an occasional cooling hand tho.

Good Luck,

Jim Henderson

 

Jim, I agree (your post #10) What a horrific memory, it must be for you. I'm talking about almost freezing to death, in a rice burner during a freezing blizzard. Terrible!! Glad you lived to tell us about it! If I lived in frigid, zero degree winter conditions, I would do what I used to do as a young man in northeast Ohio. That is, insulating your heater hoses, including top and bottom radiator hoses. I never covered the radiator, but on zero degree days, my pickup would provide me with warm, toasty heat. This helped, not only with the comfort in the cab, but provided proper warmth for melting snow and ice off of the windshield when the defrosters were on. Lastly, for towing in the summer. I've read where transmission pans, that have cooling tubes / fins provide excellent added cooling, as well as a faster cool off when the truck is shut off. This is when all vehicles experience the "heat soak" where engine and transmission temperatures (especially fluids) rise significantly for 10-12 minutes before the normal cool down cycle starts. ED

 

Good advice all. I just posted the thread about Frantz filters as I am thinking about adding a cooler o my '05 Escape for my camping trips when I'll be hauling some load. Otherwise I drive mixed commuting driving.

I'm wonderig about whether to add a trans oil cooler like the stock add-on towing package (that did not come on mine) along with a secondary filter. Same for the engine oil, so I'm wondering about a dual actiuon cooler and secondary filters for both engine and ATF.

I am also adding an air induction kit, a Gibson catback and and SCT Xcalibrator tuner. Do those add-ons suggest needing the coolers and extra filters? I live in the San Francisco area, so it rarely gets below freezing in winter.

 

In general you want an engine to be nice and hot. Hot is good. Cold is bad. Some say " heat destorys your engine", but thats simply flawed thinking. Heat is a biproduct of friction and combustion, to a point, the hotter the better. You want the oil to be hot so it lubes the motor nicely. Eventually youll start warping heads and blowing gaskets out and it will cause disastor. But make sure you run a minuum 180F thermostat, also I would think covering the radiaotr wouldnt do anything since the hot coolant in the engine is isolated from the radiator until the thermosat opens.

 

Methinks a lot better option would be a thermostat for the oil cooler that opens up at a given temperature and routes the ATF through an external cooler.

 

Perma Cool makes a thermostst: http://www.perma-cool.com/Catalog/Cat_page14.html