180 Thermostat Results (With Towing Data)

Jon A · June 28, 2015

I decided to take advantage of the hottest day of the year so far and collect some data to evaluate the cooling system to see if I was in urgent need of any other upgrades (separate Engine Air-Oil Cooler, bigger Transmission Cooler, bigger radiator itself, etc). Besides, the cab of my GMC is the coldest place I can find! Since there seems to be much misunderstanding of the effect a cooler thermostat might have (as well as the entire cooling system in general) on the boards, I figured I'd post up the results so people can see for themselves.

Cooling mods are a 180 degree thermostat from Lingenfelter and the fans set to come on more aggressively in the tune, otherwise the cooling system is stock. I do not have the NHT radiator. I have 34" tires with the stock 3.42 gears (for now) with the 6-Speed and 6.2. Here is how I have the fans programmed:

Compared with stock:

With the new thermostat and fan settings, in most driving conditions both engine oil and coolant run around 30 degrees cooler than they did stock. The stock thermostat had 207 stamped on the bottom and a 207 degree opening temperature matches prior data (coolant temps 208-212 even in cold weather) so roughly 30 degrees makes sense. The transmission temp in easy driving remains the same due to its separate thermostat. But easy driving doesn't mean much. What matters is how the cooling system does in really harsh conditions (which is also where many say the thermostat will make no difference).

So, I loaded her up:

Headed up Snoqualmie pass (20 miles to the top from the scales) on a toasty day:

Snoqualmie Pass isn't the highest or steepest pass in the country, but it's substantial. Towing that much weight in temps this hot up it isn't something I would have wanted to try in most prior 1/2 tons (and many older 3/4 tons) so I felt it would be an instructive test.

The results were pretty impressive in my opinion. I was a bit surprised actually.

For the first 10-15 miles where there is quite a bit of elevation gain, the coolant temps ran around 195 and the engine oil held around 215. The fans were running mostly well below 50% speed. Even this portion of the test, while not the toughest, is still tougher than you'd encounter on about 99% of the roads in the country.

The last 5 miles or so, where it gets really steep and the truck had to downshit into 3rd gear, the temps climbed up a bit more but seemed pretty stable at the top as the fans had ramped up. I think if the pass would have continued temps may have gone up a couple more degrees but probably not much. The fans weren't even at full speed yet. The max temps were:

Engine Coolant: 208

Engine Oil: 234

Transmission Fluid: 207

With the stock setup, I would expect temps 20-30 degrees higher at least.

Here's a screen shot of the data at the very top:

I thought that was pretty impressive. These things have vastly better cooling systems than the trucks of old. Keeping the engine below 210 degrees with only a $30 mod on such a pull--without the NHT radiator!--is really impressive. I was most worried about the engine oil temp as I had seen it go up really fast during WOT runs on the street with the stock setup, but I guess the cooler works pretty well when you actually have an open thermostat (a 180 degree thermostat will be fully open somewhere between 200 and 210 degrees) so coolant is flowing accross it. I'm running fully synthetic Redline and I don't get worried about it until about 300 so I have tons of breathing room. The transmission coolers are obviously more than adequate for towing on the highway.

And the 6.2 rocks.... Even in the very steepest part it easily maintained 65 MPH (had the cruise control set) chugging along in 3rd gear at 3400 RPM. That's with 34" tires and the stock gears. With 4.10s it probably could have held 4th.

One note--Lingenfelter has changed the design of the gasket on the thermostat as some were getting pinched by the spring (but mine works just fine) in case you're wondering why you can't order them right now. They should have the new design available soon.

Edited June 28, 2015 by Jon A

TJay74 · June 28, 2015

Good to see, pretty much the same results I have seen over the years as well. The lower stat opening also will help with intake air temps, it will also help with detonation as well. I put on all of my previous cars, need to order one for the truck and get it done this season as well.

Also make sure that the code P0128 is turned off in the tune, otherwise once it gets cold out it will trip the check gauges light. If the ECM does not see 167°+ with in so many key cycles it trips that code and kills the gauges as the ECM thinks the stat is stuck open.

bdbake01 · June 29, 2015

In for the info, but THIS is how you do it folks. Nice, nice work. Good data, good constraints, good analysis, and thx for sharing.

Jennabear · June 29, 2015

Lower temps are robbing you of your HP. The higher the temp of the oil, the more power the engine will make.

07Softail · June 29, 2015

Lower temps are robbing you of your HP. The higher the temp of the oil, the more power the engine will make.

Plus the Aluminium Heads and Block are shedding heat that is needed for an efficient engine.

RT

Jon A · June 29, 2015

The lower stat opening also will help with intake air temps, it will also help with detonation as well. I put on all of my previous cars, need to order one for the truck and get it done this season as well.

Yes, that's definitely noticeable. My AIT's usually run about 2 degrees or so higher than ambient when cruising on the highway but when things warm up and the fans increase speed this goes up noticeably. On this run it only climbed to about 10 degrees over ambient at the very top; if the radiator is 30 degrees warmer when that happens it's much worse.

Also make sure that the code P0128 is turned off in the tune, otherwise once it gets cold out it will trip the check gauges light. If the ECM does not see 167°+ with in so many key cycles it trips that code and kills the gauges as the ECM thinks the stat is stuck open.

That's a good point and something people should watch for, but it should only be a possible issue with the 160 or 170 degree thermostat (which are also available). With the 180 (unless it's leaking) you're fine. In general I don't recommend going colder than 180 to people with trucks as they're typically what is driven in the winter time. Corvettes and Camaros not so much...

Lower temps are robbing you of your HP. The higher the temp of the oil, the more power the engine will make.

I think maybe you looked at the wrong numbers? The oil heated up to 234, which is higher than normal operation. I'd be willing to bet if the coolant and oil were 20-30 degrees hotter, the higher coolant temps would subtract a lot more power than the thinner oil might add. 0W-20 is pretty darn thin even when cold, at 234 it's very thin. In fact, if I towed like this really often I'd run a thicker oil for better protection even if it did cost a couple HP--maybe not quite 15W-50 racing oil, but certainly thicker than 0W-20.

Plus the Aluminium Heads and Block are shedding heat that is needed for an efficient engine.

When towing up a hill like that in hot weather, a small advantage in mileage is not what you're typically worried about. You want to make it to the top without any flashing warning lights or steam billowing out from anywhere. In normal driving I have noticed no difference in mileage. The tiny theoretical advantage warmer engine temps may offer are largely (maybe completely?) offset by being able to run more timing.

nando87 · June 29, 2015

This is a great write up!

I have a BIG problem with heat on my 5.3 w/ 3.42 gears when towing, I've even had my truck tell me to pull over and run the truck at idle due to My Oil Tempe being to high!!

This happened about 3/4 up a very long hill pulling about 8-9k going 65mph, there was a lot of traffic and no where to pull over so I couldn't run the truck at idle I just had to back it down to about 55mph and hope for the best.

Due to my heat problem I don't want a tune in fear that something might blow and then I'm screwed even though I know the fan change will help drastically!

BUT I'm very interested in the thermostat change!!!

Do you think by just changing the thermostat will show decent results?

nando87 · June 29, 2015

Also, I'm running 33x12.50 MT tires, AFE intake and exhaust.

TJay74 · June 29, 2015

As said oil temps will be fine, you want oil up to temp to burn off moisture but not so high that is causes the oil to degrade. Higher temps all around have a negative impact on power production and will also help cause detonation.

Manufactures run the 187° factory stat for fuel mileage reasons only, they want the engines to run hotter to burn off as much of the hydrocarbons as possible, makes for less work that the catalytic process has to handle.

I would rather see the lower IAT temps, less detonation while running 91/93 octane and lower coolant temps personally.

redwngr · June 29, 2015

Do you have a screen shot of the run with the same load up the same grade with the stock set-up?

Edited June 29, 2015 by redwngr

[email protected] · June 29, 2015

This is a great write up!

I have a BIG problem with heat on my 5.3 w/ 3.42 gears when towing, I've even had my truck tell me to pull over and run the truck at idle due to My Oil Tempe being to high!!

This happened about 3/4 up a very long hill pulling about 8-9k going 65mph, there was a lot of traffic and no where to pull over so I couldn't run the truck at idle I just had to back it down to about 55mph and hope for the best.

Due to my heat problem I don't want a tune in fear that something might blow and then I'm screwed even though I know the fan change will help drastically!

BUT I'm very interested in the thermostat change!!!

Do you think by just changing the thermostat will show decent results?

Yikes. No doubt you have heating up issues. That's a lot of speed for the weight up a hill with bigger heavier tires.

Sent from my SM-N900W8 using Tapatalk

nando87 · June 30, 2015

Yikes. No doubt you have heating up issues. That's a lot of speed for the weight up a hill with bigger heavier tires.

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Yea, it heats up very fast and doesn't cool down very fast either.

My tranny is around 250 to when towing up hill

gone_fishing · June 30, 2015

Thanks for the information Jon A. Do you think you could collect this same data but when not towing? I would be curious to see your temps after fully warmed up during normal driving conditions.

I wonder if Lingenfelter could figure out how to replace the OEM transmission thermostat? If the transmission cooler is regulated by a thermostat, one that opens at a lower temp would probably aid in keeping transmission oil temps lower when towing.

Also I was curious what program you are using to collect this data? Looks like some sort of Windows application.

Spurshot · June 30, 2015

Fernando,

You have several things you can do to help with the temps. Adding/changing Fans and/or Fan programming. increased radiator capability. Increased or add oil cooler capability. Add or increase Transmission cooler.

I recall another trick one or two of the old Bonneville racers would do to their tow vehicles for the trips to Utah speed week. Put a couple jerry cans of water in the bed, run a hose over the roof to the engine compartment, wire a small water pump to a switch and make a temporary spray bar in front of the radiator. This dramatically cools everything, if the issue is only for extreme corner cases such as especially on steep hills on extremely hot weather, towing an unusually heavy load.

nando87 · June 30, 2015

Fernando, You have several things you can do to help with the temps. Adding/changing Fans and/or Fan programming. increased radiator capability. Increased or add oil cooler capability. Add or increase Transmission cooler. I recall another trick one or two of the old Bonneville racers would do to their tow vehicles for the trips to Utah speed week. Put a couple jerry cans of water in the bed, run a hose over the roof to the engine compartment, wire a small water pump to a switch and make a temporary spray bar in front of the radiator. This dramatically cools everything, if the issue is only for extreme corner cases such as especially on steep hills on extremely hot weather, towing an unusually heavy load.

I think I'm going to get a tune, get the fans going asap and put a mild tune on so I don't risk the motor to much.