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Wild one

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@danielmid , I guess I forgot to consider the thermostat goes from fully closed to fully open across a RANGE of temperature. So, say you've been on a highway stretch for an hour, unloaded, and the engine temp is steady at 210 F, the thermostat may still be semi-constricted, thus still in the equation and keeping your temps up. You'd have to know at what temperatures the thermostat (1) starts to open and (2) becomes fully open at.

Huh. It would be interesting to get an old thermostat and run a little experiment on it to see what those two temperatures are. But also completely useless. I'm also just realizing now that water boils at 212 F. That explains why they like to get engine oil up to at least 212 F, to boil off any water that might have made it around the piston rings and built up in the crankcase.
Water only boils at 212 at sea level,the higher you go up in elevation,the lower the boiling point becomes.I've ran lots of vehicles with a 160 thermostat,and have never had any water condensation in the oil when i drain it,so i question that theory of needing oil temps of 212 or higher to boil off the water.Water will evaporate even when it's frozen solid,case in point look at an ice cube in your freezor after it's been there for awhile.I like oil temps of 200 alot more then i like oil temps of 220 or higher,the hotter the oil the thinner the oil film protecting moving parts. Just my 02 of observing engines and more importantly blown up engines (i've had more then my share of blown up engines,lol) over the years. Rod bearings in particular don't like thin oil films as the cushion factor is less
 
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Daniel Ortiz

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@Wild one , I looked it up, and I live at 154 ft above sea level. And that's since I moved from my last house that was at 114 ft! Google says I still get to deal with 212 F unfortunately. Anyway, as you say, that's just the theoretical starting point. There are a lot of other factors at play, but it does show one of the big starting factors.

I like that we can start to see the trade-offs the engineers have to wrestle with when they set these design points. Hotter oil = less water over time, but thinner oil. Cooler oil = more water over time, but better protection. I guess that's a good reason to not go for looong oil change intervals if you're running it at cooler operating temperatures, or if you rarely get up to operating temps at all, such as many short drives.
 

blackbetty14

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