Which thermostat to get?

[rubbersoul]

I need a new thermostat and saw that Bav Auto offers three different ones: 71 C, 75 C, or 80 C.

I live in Michigan and drive my car in three seasons. I was thinking 75 but don't know if it will affect my heat during cooler days in the fall and early spring.

Thanks

[g323]

i used the 80 in California. Theoretically you get the best gas mileage if it's hotter because your car leaves the warm up cycle quickest, also by running slightly hotter your combustion system is more efficient and you get more power unnoticeablly . Also, your oil will also heat up faster leading to less wear on parts should you gun it before it reaches opperating tempreture. Since your in cold country I would say 80 without doubt.

[kdanielson]

I prefer the 71C thermostat but I get stuck in traffic during my commute sometimes. It gives me a little cushion before it gets too hot.

The temp of the thermostat doesn't make a difference on how fast the engine warms up, only on when it starts letting water to the radiator and 71C is warm enough for heat in 30*F weather.

ken

[epmedia]

80 is good if your engine is not all wore out. Otherwise go with the cooler ones.

If you are unsure, go with the 75?

Robert

[g323]

I prefer the 71C thermostat but I get stuck in traffic during my commute sometimes. It gives me a little cushion before it gets too hot.

The temp of the thermostat doesn't make a difference on how fast the engine warms up, only on when it starts letting water to the radiator and 71C is warm enough for heat in 30*F weather.

ken

Ken,
Wouldn't it make a difference in how fast the engine warms up by allowing it not to start to cool itself off until it reaches 80c instead of 71 or 75c?

I thought that at the designated temperature(80 75 or 71) the coolant in the engine starts to flow into the radiator and from the radiator into the engine to cool off the engine.

[TheBestCow]

I was wondering the same thing, but for Birmingham. The last time I had that discussion on here a 75 degree seemed like a good middle of the road. Not sure about Michigan since you actually get winter up there.

[epmedia]

I think the 80c is stock. The only time I think it should be a lower temp thermostat, is if the engine is wearing out. When an engine is new, it's tight - higher temp to expand the metals for designed clearances. When the engine is loose, a lower temp thermostat will expand the metals less.

Example: back in the '80s marine engines ran on a 165F. thermostat, and the engines were built with larger clearances on the metals (between the cyls and crank), compared to 180/210f for automotive engines. These are approx figures, it's been awhile!

Robert

[TheBestCow]

Dumb question: how would you define the engine wearing out? Losing pressure at the cylinders, or...?

[epmedia]

Dumb question: how would you define the engine wearing out? Losing pressure at the cylinders, or...?

Pressure loss from the cyls could be valve seats, irrelevant for this topic, otherwise the piston rings:

I'd say 200k miles for the mid range thermostat on a well maintaned, good running e21.

1) When you change the spark plugs, is there any oil fouling on them?

2) Does your engine burn much oil - ie: blue smoke (oil leaks are irrelevant)?

3) Does your engine oil smell like oil, or fuel, or both?

Robert

[mxl556]

75 is the best IMO.

[younggune21]

if you dont mind the slightly longer time to get heat in your cab then go with the 80 your car should still run at the same temperature when warm as a 71 or 75 but the 80 will let your engine warm up more before it starts to allow coolant to flow, which in the winter will lower the coolant temp more rapidly, so a higher initial temperature will result in a slightly higher temp when the thermostat does open, but the operating temperature figureing you have a sound cooling system will be the same

[kdanielson]

The temp on the thermostat is the temp it tries to keep your engine at. A 71C thermostat will cycle open and closed to keep the engine at 71C if the cooling system is fully functional. All three thermostats will heat the engine to 71C at the same rate, the others just keep closed longer before cycling. By 71C the engine is well out of warm up mode.

ken

[younggune21]

your engine operating temp should be around 190-210 depending on what they are designed to operate on, i have never seen a cooling system function well enough to have the thermostat cycle open and closed once the vehicle is warmed up, the thermostats only purpose is to isolate the block during warm up to get to operating temperature quicker

[AE101]

The temp on the thermostat is the temp it tries to keep your engine at. A 71C thermostat will cycle open and closed to keep the engine at 71C if the cooling system is fully functional. All three thermostats will heat the engine to 71C at the same rate, the others just keep closed longer before cycling. By 71C the engine is well out of warm up mode.

ken

exactly.

I'm in eastern canada, I'm running the 71*C thermo, with the 82*C aux fan switch. No worries.

[EgoTrippingOut]

yea, the 80*C is stock. Unless you have some sort of reason to change it, I'd stick with the 80.

[BaronOfIpanema]

your engine operating temp should be around 190-210 depending on what they are designed to operate on, i have never seen a cooling system function well enough to have the thermostat cycle open and closed once the vehicle is warmed up, the thermostats only purpose is to isolate the block during warm up to get to operating temperature quicker

It seems 71 C = 159 F and 80 C = 176 F. According to your numbers the 80 C thermostat should be just fine for most, a? I did notice that mine (71 if I recall) did run pretty cool during the shoulder seasons. Maybe I'll replace it with stock next time I get in there.

[rubbersoul]

Well, I ended up ordering the stock 80C. It's what I am taking out and never seemed to have a problem with it when it was operating properly. Thanks guys for the input though. I never would of thought of the things you guys brought up.

[unicorn]

This is a deserving social media thread. Thanks for this forum.

[winmag4582001]

Here's my experience with thermostats. They regulate the initial opening of water flow. That's it.
When I replaced the thermostat in my 2010 Ford, factory was 195 degree, replaced it with a 180 degree. Normal operating temp of 202 degrees didn't change. Weather it opens at 150 or 200 would not make a difference at operation since that is controlled by the size of your radiator and flow amount of your water pump.
A new radiator, water pump or antifreeze would have a greater impact on operating temps. Just my experience....