I recently visited my brother in another state, and we took a little day trip in his 2009 BMW 328i. I did the driving, and I noticed the temp gauge was marked in degrees Fahrenheit and that the running temp was 240° (just below the 250° mid-point on the gauge).

Presuming the gauge was accurate, I wondered why 240° is okay for that engine and not okay for the Rover V8 in our trucks.

Your thoughts, please?

 

Engine design, most iron V8s run between 195 and 220 and aluminum V8's are pretty much the same. For our V8's overheat is 244F.

Disco owners worry more because our cooling system is a bit marginal so when we start to overheat things get hot fast

 

Its not ok for the BMW either. They don't give two ****s about engine longevity as long as it makes it out of the warranty period. In fact, BMW engineers take the view that the engine/car is ready for retirement once it reaches 100k. At that temperature the oil is very thin and even a minor cooling system excursion results in a blown engine. Guys on the BMW forums are starting to figure it out as they approach high mileage and are getting pissed. BMW runs them that hot to maximize fuel economy and emissions by intentionally thinning out the oil, but no one wants their race car at that temperature. People will say "the engine was designed for it" . By the same dumbass engineers that put the bypass thermostat in the D2, the plastic crossover pipe at the rear of the heads on a RR, timing chains at the back of an audi, and the disasterous timing chain tensioners on the BMW 4.4. Just because they are engineers does not make them infallible, and their motivations are much different than yours.

 

It's probably not actually at 240 - might just be a nice round number for the gauge (or a translation from a nice round number in degrees Celsius). Hook a scan tool to it and it'll probably be between 200 and 220.

 

All cars I have owned run around 200 Fahrenheit Hondas Subarus dodge ford etc dammm even hot water boilers big and small the high limit is 180 - 200 max you don’t want to run any liquid past 200. Boiling will kill things fast. Heat kills

 

@mln01 The gauge on the F30 BMWs (The 2009 328i is an F30) shows oil temp, not coolant temp. Under normal driving conditions it should run between 230 & 250. (I have owned four BMWs) It is annoying they run them that high since SAE rates oil viscosity at 212 degrees, but, that's what BMW intended.

 

Was reading an SAE paper yesterday on timing chain wear compared vs three oil types, mineral, semi-syn, and full syn. Full syn had half the wear rate of the other two, and we know mineral and semi-syn do not have the same temperature resistance as the full syn. Full syn only on those DOHC engines guys.

 

Found this - For a dual-purpose car, engine oil needs to be at least 220 degrees F to burn off all the deposits and accumulated water vapor. For every pound of fuel burned in an engine, the combustion process also generates a pound of water! If engine sump temperatures rarely exceed 212 degrees (water's boiling point), the water will mix with sulfur (another combustion byproduct) and create acids that can eventually damage bearings. As for ultimate power potential, the general consensus among most racers is that hot oil and cool water make more power in most engines. Cold engine oil causes excessive frictional drag on the bearings and cylinder walls. A quality conventional motor oil will tolerate oil sump temperatures up to 250 degrees, but starts breaking down over 275 degrees. The traditional approach is to try to hold oil temperatures between 230 and 260 degrees. Even on a short-duration, drag-only combo where oil is frequently changed, you would not want to routinely see oil temps under 200 degrees.

 

My 2018 Range Rover (supercharged V6) would cruise on the highway at an average temp of 240 but would oscillate between 225 and 260, totally within spec ¯\_(ツ)_/¯ Just different motors, different designs. Pretty wild.

 

My dad had an F30 that I drove a few times. Ashamed to say I never realized it was oil temp… I thought it was coolant temp as well this whole time. 240 degrees oil temp is about right for a modern car with full synthetic oil. Probably similar to what Discos run really.

I feel dumb. Every time I would tell him “your car runs really hot!” Haha