4.8is Rev LED indicators - based on what?
 

So we all realize that revving up an engine with cold oil is not a good thing. Kind of like trying to stay lubricated with honey = bad. The rev indicators try and warn us of this on the M cars, 4.6is, and 4.8is. But what are they based on? As far as I can tell, it looks like they are based off of water temperature which really isn't the best thing right? It should really be based on the oil temperature in my opinion. I was really hoping that these wouldn't just be idiot lights and would have some meaning behind them, but so far I've been kind of disappointed. Even when the oil temp is below 120deg F or so they all go out.

I don't know about you, but I wouldn't rev up any engine of mine until the oil is up to temp - say 160deg F or higher. Maybe I'm being too paranoid or the oil temp sender is slow to respond? Anyone else have this exp?

i follow the light up gauges 80% of the time.. but also like you, even after all the lights dissapear, and im like okay its fine to floor it, ill look at the oil temp gauge and be like "hmm maybe i should wait for that to go up too" so i know where ur comin from

When I took delivery of my 4.8is, the dealer told me it was based on water temp, so I guess that's it.

For sure, when it is -14 degC outside, the LED lights go out long before the oil temp gauge starts moving at all. I don't rev it much past 3500 until I see some movement on the oil temp gauge.

John

water temp, man that's strange that they would do that. I tend to wait until the second mark before getting on it as that should be around 165deg F.

my 4.6 is at operating temperature (water wise) long before my LEDs start dropping off

I agree, I always wait for the oil temp guage to get about a 1/4 of the way (exactly in between the 120 and the 210) before I start to give it any gas, usually keep it below 2500rpm until this occurs

I just confirmed again tonight that the LED's drop completely out as soon as the water temp comes up to operating range. Sometimes my oil temp is still at or just slightly above 120degF. This sucks! Another idiot gauge and I thought there was some engineering behind it. Sigh.

Well, I think the term idiot gauge sums it up.
There are many ways that BMW could have imposed a "limit" on engine revs when cold - i.e. electronic rev limiter etc.
You have to look at why BMW whould have put the lights there at all - it's because some people will rev a car hard when cold and damage the engine.....and then take it back to BMW to fix under warrenty.
So, whilst measuring water temp is not a good indication of the whole engine temperature- its stops (or at least shows) the idiots that they are doing something they shouldn't be!

I wonder if this is a difference between the 4.6 and 4.8 just the first two leds drop off once my oil temp is half way through the first 1/4 (prob 130 or so) and respectivly go down from there...I wonder if the 4.6 is oil temp based

Does the last one go out when the oil temp is all the way up or is it sometime before that?