E92/328 operating temperature

[TwoE46s]

My wife recently brought to my attention that the op temperature on our E92 / 328 is running about 230-240 degrees.

Is this what the rest of you are seeing???

Regards

[markusmark]

I don't have an E9X yet, but my E46 is my 4th BMW. The temps you quoted are fine. I installed oil pressure and temp gages in my last car, a 1985 325e. The oil temps would run close to 200 degrees under most circumstances. And, that was with Mobil 1 15W-50 oil.

Most modern engines run at higher temps as a means of improving efficiency (fuel mileage). That's why manufacturers switched to synthetic oil years ago. No "organic" oil can withstand modern engine temps.

BTW, the 335i (with twin turbos) has a max oil temp of 300 degrees. The car reverts to "limp" mode when that temp is exceeded. This done to prevent damage to the engine. That engine is the same basic engine that's in your car!

[chrisross2345]

I have a 2007 328i and I run about the same. I have a few friends with the same car (older models) and they also say that it's standard.

[TwoE46s]

Thanks for the input. Anyone else please feel free to chime in on your observations with 328s. Unfortuneatly on E46s you don't get an actual temp reading, but just the "cold"-"medium"-"red/you're in trouble" readings, so it's hard to compare.

I have read a lot about the extremely high temps on the 335/535, but was not aware that it was getting to 300 degrees before it went into limp mode. Actually this is something that I will continue to pay attention to as I think about replacing the wagon and the 535 is at the top of that list. While at the same time I am not very comfortable with that high of operating temperature if for no other reason, there is no reason for it to be. Very concerning that BMW may have put themselves against the wall on this one - enhance the cooling in newer models and drop the temp to where it really should be, and they open themselves up a potential liability for a "recall" type fix on the current cars...............

Regards

[markusmark]

Actually, the higher the operating temperature the more efficient the engine. It's purely a matter physics.

[TwoE46s]

Originally Posted by markusmark

Actually, the higher the operating temperature the more efficient the engine. It's purely a matter physics.

I certainly understand that engines have "optimum" operating temps (most seem to in the low 200s, while my CaymanS runs at 175 all day, with 250 being in the red), but do not grasp that "higher" temps such as pushing 300 degrees is necessarily more efficient....... Higher heat is obiously harder on the engine components themselves, so I'd greatly appriecate your insight on the physics of this. Thanks!

[markusmark]

Originally Posted by TwoE46s

I certainly understand that engines have "optimum" operating temps (most seem to in the low 200s, while my CaymanS runs at 175 all day, with 250 being in the red), but do not grasp that "higher" temps such as pushing 300 degrees is necessarily more efficient....... Higher heat is obiously harder on the engine components themselves, so I'd greatly appriecate your insight on the physics of this. Thanks!

Let me explain the "higher temp = greater efficiency" theorem. Don't fall asleep, there will be test.

Every gallon of gasoline, regardless of octane, contains the same amount of energy - thermal energy. "Octane" is merely the gasoline's ability to resist pre-detonation, aka pinging and knocking. Pinging and knocking are symptoms of uncontrolled and uneven burning of the fuel/air mixture.

Engines that are designed to run at relatively low internal temperatures are incapable of extracting as much thermal energy from the gasoline as engines that are designed to run at higher internal temperatures. The latter group of engines is literally extracting more heat (thermal energy) from the gasoline than engines in the former group.

Viewed differently, lower internal temperature engines send a greater proportion the gasoline's thermal energy out through their exhaust systems that do engines that are design to run at higher internal temperatures. That is, they are less efficient.

How do engine designers "design" an engine to be more efficient? One way is to raise the compression ratio. Modern engines such as those in our BMW's have significantly greater compression ratios that engines of the 1980's and earlier. The 3L engine in my 330Ci has a compression ratio of 10.4:1. I remember growing up in the 1960's when cars typically had compression ratios in the area of 8.5:1. I think the Covettes of the era had a 9.2:1 compression ratio. Hot stuff!

Higher compression ratios have typically been mentally connected with "hot rods" and other high performance cars. But with advent of modern engine management electronix, high compression engines can use gasoline with a less than optimal octane rating without damage. Our engines have 2 (or is it 3) knock sensors. Basically, these are piezo-electric devices that respond to specific "noise" frequencies (pinging and knocking) by generating a small electrical signal. When one of the sensors "tells" the engine management computer that it "hears" a noise (pinging or knocking), the computer retards the spark, decreasing the chance of ping and/or knock.

HTH YMMV

[Johnson023]

Its a safety thing so people can see your car from the side when it is dark - Sedan has it built into the side of the headlight I believe which is much harder to get rid of!