Help with thermostat please

[mistertonylee]

So I'm just wondering. I have an m20 325e from 1984. It apparently has the lowest them oe thermostat as the temp stays well below half. I'd like to know what temp the closed loop operation of the engine starts/stops while it's warming up if anyone knows. Basically, do I need to install a 180 degree thermostat instead of this one to save some gas?

Thanks, Tony

[Sagaris]

Your engine will run most efficiently with the hottest (numerically highest) thermostat available. I would run the stock thermostat, I take no responsibility for the longevity of your engine and related parts if you choose to be frisky and run something hotter than the stock thermostat, but engines run more efficiently when they run hotter, if the block, head, ring, and piston material could handle extreme heat , there would be no need for a cooling system. Unfortunately such ideal materials do not exist at the moment.

[mistertonylee]

Thanks for the reply. 180 deg. is stock. But for some of the hotter climates (I'm in NC, bought the car in SC) BMW put in a lower temp one, I think 160. That's what I have and it seems really low. I'm just wondering about the fuel mapping at those temperatures.

[jlevie]

The DME does increase fuel deliver as the engine temperature drops, so if you are interested in fuel economy and have a 75C thermostat replace it with an 80C thermostat.

[nando]

Your engine will run most efficiently with the hottest (numerically highest) thermostat available. I would run the stock thermostat, I take no responsibility for the longevity of your engine and related parts if you choose to be frisky and run something hotter than the stock thermostat, but engines run more efficiently when they run hotter, if the block, head, ring, and piston material could handle extreme heat , there would be no need for a cooling system. Unfortunately such ideal materials do not exist at the moment.

a 5c increase in temp is not "extreme"

[mistertonylee]

Excellent! Thanks to everyone for their replies. I just didn't want to change it out if there was no benefit.

Tony

[Sagaris]

a 5c increase in temp is not "extreme"

Of course it isn't, I was stating the fact that the only reason a car needs a cooling system is because the materials that the engine is composed of cannot handle the heat without it, but, that if such materials existed, then engines would not use cooling systems due to the improved efficiency that can be had from operating at higher temperatures. However, I am not aware of the highest temp. thermostat that a parts store may offer, and a high mileage car with a weak head gasket or other weak components may fail under the added heat which is why I posted the quick disclaimer.

[mistertonylee]

Update: I just installed the 180 degree thermostat. The temp now goes to halfway up the dial. Also, I did a test drive on some of the mountain roads around here at 1/2 to 3/4 throttle most of the time and a bit of highway driving around 75 mph, and averaged 24 mpg according to the obc. Before on the same roads, I averaged about 21, so a significant increase in my book. I'm looking at 36 mpg highway now if the obc is remotely accurate.