The big oil temperature swindle?

[julian64]

Just an interesting aside for M cars for anyone interested.

There doesn't seem to be any oil temperature gauge on the E39 M5, despite the fact that there is one instead of the mpg gauge on the dashboard.

It is, in fact a contrived con, or swindle as it were.

Its also an interesting exercise to ask BMW dealers this exact question. I had great fun the other day asking for a new oil temperature sender, because the dealers, even their technical staff don't seem to know where it is.

Some will offer you a new oil level sender, some will offer you a new engine temperature sender and some will offer you an oil pressure sender, swearing blind that its well know BMW misnamed it in the parts manual.

The reality, after a blinking load of reseach seems to be even stranger still.

[humpbackmaniac]

Actual oil temp can be found in the hidden menu on the nav unit. I could tell you how this can be found but its a need to know basis...........

[julian64]

That oil temperature and the dashboard one are identical, and both go wrong together.

Does that oil temp or 'OELTEMP' work on non M cars. I suspect it would as the level sensor is the same on M cars and just about every other BMW

[pat_y]

hmm, interesting, had a trawl through the ETK list for E39 M5, you are correct there is no oil temp sensor for this car. Only pressure and level.
There seems to be 2 types of oil temp sensors, early type was fitted to:
E34 M5 3.4
E34 M5 3.8
E36 M3 (3 litre)
E30 320is
(strangley the E30 M3 is not mentioned)

Later oil temp sensor was fitted to:
E36 M3 Evo
Z3 M series.

But this might be my own stupidity but i cannot find and oil temp sensor for the E46 M3 either?
(edit: just noticed your other post, might explain the lack of oil temp sensors on later M cars)

Edited by pat_y on Friday 12th March 09:47

[julian64]

There isn't an oil temp sensor. I believe its a BMW con. I used to think the oil level sensor had a temperature sensor in it in the cars with an oil temp display on the dashboard, but it simply doesn't exist.

Its the big oil temperature swindle by BMW. Effectively a gauge which is contrived to make the M cars look more M car .

As far as I can tell they use a pretty rough calculation using the oil level and the engine manifold temperature, water temperature if you will, to calculate a predicted oil temperature and then display it on the oil temperature gauge.

I'm hoping someone will come along and tell me I'm completely wrong, because if I'm right, I'm not very impressed.

[rassi]

So, you are saying that the oil temp gauge is just a "made up" one because there is not an oil temp sensor? In the secret menu, my temperatures for water coolant and for engine oil are quite different, with water normally around 79-80 degrees and the oil a good 10 degrees higher.

I would be very surprised if the oil temperature was just a "calculated" one, based on water temperature, etc!

[julian64]

Thats why I'm surprised.

I think the oil temperature is calculated from the water temperature and the oil level.

They adjust the delay in oil temperature behind the water temperature based on the amount of oil in the crankcase. The more oil, the more of a delay they estimate the oil will be behind the water.

And thats what they present on the dial to you.

I am hoping that someone will come and explain where I'm wrong but the more I look at the circuit diagram, the TIS, and investigate my car the more confident I'm becoming of what I say.

If I'm right, the oil temperture in an M BMW is a complete fabrication to pander to people who like the idea of an oil temperature gauge but without giving any meaningful information.

Or if I was being cynical, the oil temperature gauge is not there to give any meaningful information. It was contrived as a way of taking the MPG out of an M car to stop the owners seeing the mpg as a negative.

[waremark]

Isn't this a bit like the men on the moon conspiracy theory - that it would be easier to do the real thing than to make it up? Surely an oil temp sensor cannot cost much?

[TheEnd]

julian64 said:

Or if I was being cynical, the oil temperature gauge is not there to give any meaningful information. It was contrived as a way of taking the MPG out of an M car to stop the owners seeing the mpg as a negative.

That could be a good reason, although it has made a rod for their own back as i see many people worrying about oil temps when driven hard, when it was just maybe an afterthought to display the gauge to the driver.
I'll look into the wiring, and see what i can find

[TheEnd]

Looking at the M3 evo, everything comes in on pin44, and it's called "oil level switch, thermal"

the 3 wires are power, signal and ground...

[Koing]

SOOOOOO you guys are telling me the oil temp gauge in my E46 M3 is completely fabricated then??!!

Whats the deal with the MPG speak then? I can see it by the nav computer or on the dash when I flick to it. I'm completely lost.

So when can I gave it some beans then? Then the amber lights are out? I had been also 'waiting' until my oil temp got to 75C, which in light of this thread seems completely BS!

Koing

[RockyRoad]

Does it matter if the figure is derived from other sensors and accurate to within 5-6% of the actual oil temp?

I'm sure they gave it plenty of runs on the test bed to come up with the formula using alternative parameters.

[Spartikus]

Is this early April Fools?

[julian64]

Just a bump in case anyone with super knowledge can prove this is rubbish.

[john_p]

Lol, this is quite amusing. Unless the oil level sensor does it somehow ? It has three wires, but no idea how it's wired up electronically

http://m3forum.net/m3forum/showthread.php?t=256859
seems to back up your assertion

Edited by john_p on Tuesday 16th March 16:15

[julian64]

john_p said:

Lol, this is quite amusing. Unless the oil level sensor does it somehow ? It has three cables, but no idea how it's wired up electronically.


http://m3forum.net/m3forum/showthread.php?t=256859
seems to back up your assertion

The three cables are earth, 5V, and the level of the oil.

I took my old oil level sensor apart and there is no thermocouple or any other mechanism to detect temperature in it.

[E30M3SE]

E30M3's have a separate oil temp switch part # 12611309193.

That same part number is also listed for E34 M5 3.6 & 3.8 and E36 M3

[hoppo4.2]

has any one tested how accurat the gauge is?

stand to reason that if it says 100 degrees the temp of the sump/area around the level sender should be close to this. i no a bit is lost etc but a test with on of those lazer themp things should give us an idea.

personaly if the gauge is accurate (ish like all gauges) im not fussed how it finds it out.

[blondini]

Google 'As on the M5 engine, a thermal sender is employed to monitor both oil level and
temperature' http://www.google.co.uk/search?hl=en&source=hp...