Accuracy of oil life predictor

[danylo]

Hi,

I have a 2005 Buick Allure CXL and was wondering how the oil life predictor works on the dashboard. Is it just a counter (of kms) or does it use something else for prediction?

I noticed on my last oil change I was 1k km over when my mechanic said I was supposed to get an oil change (and they put a sticker for 5000 km so 6000 km since my last oil change) but according to the dashboard I still had 60% oil life left.

Thanks for the help!

 

[InfiniteImp]

My experience with this has been interesting. I have a 2010 LaCrosse. For the first 3 years, the oil life indicator told me I could do about 16,000Km until an oil change was needed. So, at 5,000Km I was showing an oil life remaining of 65%. For simplicity's sake I decided to get it changed every 10,000Km (oil life indicator said I had 30-35% remaining at that point). I got the oil changed at the dealership and they had nothing negative to say regarding my mileage.

What's more interesting is what happened when the car was 3 years old. Suddenly the oil life dropped by a half! So, at the 5,000Km point, I was showing about 30% oil life remaining. At about 9,000Km I got the warning on the display to get the oil changed.

So, based on this my conclusion is this. The oil life indicator is a money-saving or a revenue-generating function for the dealership. There are dealers who give promotions like "Free oil changes for the first 3 years of your car ownership". It looks like the car, when new, can easily do about 15,000Km between oil changes so the dealer wouldn't have to do too many in the first 3 years. Then, after 3 years, suddenly the frequency of oil changes seems to double. Why? More income for the dealers is my guess.

Some might argue that as the engine gets older it needs more frequent oil changes. I see validity in that but not at the rate it happened. It would make sense if that oil life number dropped gradually but to suddenly be cut in half?? That seems to be a pre-programmed algorithm in the car's computer.

In short, most people will tell you to get it done every 5,000Km. That's what I'm doing now. Does the car really need it done that frequently? I don't know. Based on my experience I'd say no.

 

[Mad*Max]

my experience is different, my 2010 is 4.5 years old with 76000 km and the OLM behaves the same since I bought it, it is still lethargically making its way to zero over a span of 20000 km - I however change mine at 50% as my belief is that conventional oil will not provide protection for that long, especially the way that I drive

My experience with this has been interesting. I have a 2010 LaCrosse. For the first 3 years, the oil life indicator told me I could do about 16,000Km until an oil change was needed. So, at 5,000Km I was showing an oil life remaining of 65%. For simplicity's sake I decided to get it changed every 10,000Km (oil life indicator said I had 30-35% remaining at that point). I got the oil changed at the dealership and they had nothing negative to say regarding my mileage.

What's more interesting is what happened when the car was 3 years old. Suddenly the oil life dropped by a half! So, at the 5,000Km point, I was showing about 30% oil life remaining. At about 9,000Km I got the warning on the display to get the oil changed.

So, based on this my conclusion is this. The oil life indicator is a money-saving or a revenue-generating function for the dealership. There are dealers who give promotions like "Free oil changes for the first 3 years of your car ownership". It looks like the car, when new, can easily do about 15,000Km between oil changes so the dealer wouldn't have to do too many in the first 3 years. Then, after 3 years, suddenly the frequency of oil changes seems to double. Why? More income for the dealers is my guess.

Some might argue that as the engine gets older it needs more frequent oil changes. I see validity in that but not at the rate it happened. It would make sense if that oil life number dropped gradually but to suddenly be cut in half?? That seems to be a pre-programmed algorithm in the car's computer.

In short, most people will tell you to get it done every 5,000Km. That's what I'm doing now. Does the car really need it done that frequently? I don't know. Based on my experience I'd say no.

 

[BIG ROCCO]

The OLM counts engine revolutions, then factors input from many sensors to adjust for things like throttle position, engine vacuum, engine RPM, engine load, trip length, and coolant temp. I don't know what the "revolutions to empty" # is but let's pick 1 billion as an arbitrary #. So, the engine can turn 1 billion times before the oil needs to be changed...but that is under the most ideal conditions, which might just be at idle with engine running continuously. Every revolution that takes place with the coolant below normal operating temp might count as 10 or 20 or 100 revolutions. Every revolution with the throttle angle more than 20% might count as 5 revolutions, more than 50% might be 12 revolutions, wide open throttle might 44 revolutions. This is how the OLM was explained by a GM powertrain engineer on the Cadillac Forums I used to frequent - also look here:

http://www.cadillacforums.com/cadillac-tech.html#oillife

 

[Benzadmiral]

The OLM is sophisticated enough that it reports differently for different engines. My '03 Park Avenue would count down more slowly when I was on a highway trip, faster in the regular 70% city driving I do. For me, 5000 miles/6 months was a good oil change point to remember; but I would have 40% of the oil's life left at that point -- so only about 10% drop per month. It certainly didn't change as the car aged -- I drove the PA from about 50K miles to 110K, and the OLM worked the same.

In contrast, the OLM in my '11 Regal (NA 2.4 engine) seems to drop at 1 point for every 60 miles, 15% a month, no matter what the outside temp is, no matter what my mix of highway driving is. Last May, right after an oil change, I ran 2000 miles round trip to Amarillo, TX, 98% highway. The OLM dropped about the same as if I'd spent those 2000 miles over 2 months, driving to work and running errands. Not to denigrate the OLM: I think it's set up for different engines. That in the PA was the old-school, low-revving 3.8 V6; the Regal contains a different animal, one prone to fuel dilution and possible deposits. So changing at 4000-4500 miles, 5 months' driving for me, seems sensible.