Oil Service and Inspection Lights, trust them?

[solanog]

Supposedly when the Oil change indicator light lights up you should change your oil, o.k.
My question is how bad is the oil at this point, does this light comes on after certain kilometers or after certain time (weeks, months)? What really makes it light up?
My father's X5 had an oil change about 3500miles ago and now the oil light is on. It was reseted when the change was done. Isn't to short time? It is using Mobil 1 0w 40 supposedly LL01 which is what the car needs according to the manual. It's a 3.0diesel X5.

[dannyb]

I think it goes by km/miles ... I just reset it and continue on with life.

[Teh Prof]

I ignore the lights and change oil every 3K miles.

[dvmotorsports]

Originally Posted by solanog

Supposedly when the Oil change indicator light lights up you should change your oil, o.k.
My question is how bad is the oil at this point, does this light comes on after certain kilometers or after certain time (weeks, months)? What really makes it light up?
My father's X5 had an oil change about 3500miles ago and now the oil light is on. It was reseted when the change was done. Isn't to short time? It is using Mobil 1 0w 40 supposedly LL01 which is what the car needs according to the manual. It's a 3.0diesel X5.

I'm thinking that the oil light was on originally. The new light I would believe is the inspection light. How many miles? I have never seen an oil light come back on that fast. It's usually 12,000K miles (21,xxx km) up to 20,000 miles (36,xxx km). "M" cars may be different.

[solanog]

Originally Posted by dvmotorsports

I'm thinking that the oil light was on originally. The new light I would believe is the inspection light. How many miles? I have never seen an oil light come back on that fast. It's usually 12,000K miles (21,xxx km) up to 20,000 miles (36,xxx km). "M" cars may be different.

This one is a regular X5 with the sport package. The light was reseted at the Oil change that was at 55 000 km it came back again at around 61 000km. I seems like to soon since I've read that oil changes are recommended at around 7500miles.
Does this lights have to do something with how the car is driven or do they have some sort of sensor for the oil and can analyse the oil wear and tear? Does diesels need more frequent oil changes?

[AlpineSixAndSeven]

yes it does... yes and diesel's do need more oil changes.... i sugest like teh prof. said every 3k. and reset the lights when needed......

[AlpineSixAndSeven]

here are the "Technical details of the service reminder lights."

Mileage is estimated based on the following formula:

e= a(1+t+r)

e=Estimated mileage
a=Actual mileage traveled
t=1 if engine temperature is below operating temperature, else t=0
r=.5 if engine is above 4500 RPM, else r=0

Example: If you traveled 5 miles with a cold engine running at 5000 RPM, the SII computer would actually "estimate" 12.5 miles traveled:

Solving for e:

a=5 (the actual miles traveled)
t=1 (because the engine was cold)
r=.5 (the engine was exceeding 4500 RPM)
e=5 X (1+1+.5)=12.5 estimated miles (from a trip of only 5 miles)

Once the computer reaches a certain count value (about 7,500 miles for Oilservice and 15,000 miles for inspection, varies from years/models), it will illuminate one of the service lights (oilservice or inspection).

[Teh Prof]

I have driven 17,000 miles on one set of oil service lights before it told me to get my oil changed. I can't imagine how gunky things would get if I actually cared about them.

[AlpineSixAndSeven]

... 740 it down to 1 green light...... sad $80 in oil again.....

[solanog]

Thanks for that formula. Now this confuses things more since this car is diesel so redline is around 4500 rpm, it takes very little for the car to reach more than cold engine temperature since I live in the tropics (Costa Rica). So estimated mileage should be close to actual mileage. Maybe since we have many hills (where we live we have far from flat geography) maybe we demand more from the engine than in other places.

[dannyb]

Just check your oil on a weekly basis and change it when its needed.