Oil life monitor on Buick Rendezvous...

I have had oil analysis done on Mobil 1 drained out of our Olds when the monitor said 20% left, and the oil analysis people indicated that the oil still had plenty of useful life in it.

IMO, GM's oil life monitor system is pretty sophisticated as it takes into account start up cycles, engine rpms, engine loading, etc. All of these are real factors which effect oil's useful life. GM's system assumes standard motor oil, so by using synthetic you are buying yourself significant extra safety margin.

I now run Mobil-1 in our GM vehicles until the oil life monitor gets down to around 15% useful life remaining and then I go ahead and change it. This interval can end up being as short as around 4500 miles if the use is mostly around town driving or almost 10,000 miles if long cross country highway trips are involved. This procedure is still very much overkill and I could be running the oil longer on synthetic ... but I have not been able to bring myself to do so.

If you really want to be sure, spend $25 on a professional oil analysis of your situation.

is the place I have used.

John

Outstanding information on thier website...thanks for sharing Eightupman

I think you will find individual differences from one GM to another.

On mine, for each start-up, if I go less than three miles, then it counts that up toward a 3000-mile oil change. If I go more than three miles, then it counts that up toward a 7500-mile oil change. Then the oil life is calculated from that and displayed on the dash in terms of percentage remaining. Since I nearly always go many more miles than three, mine nearly always counts toward 7500 miles. However, since my driving is a mixture of easy and hard, I always have the oil change at 5000 miles.

---Bob Gross---

** To email a reply, please remove everything up to and including the underscore in my email reply header.

What do you base your suggestion on? Do you have any data? I doubt it. It sounds like you are simply repeating a decades old rule of thumb. In the real world oil life varies dramatically as a function of engine design, driving conditions, etc.

John

Here's the story directly from the horse's mouth:

questionable.

No, when was that?

Yes, the system changes from one GM to another. Mine is quite different.

---Bob Gross---

I think it was on a memo they put out. They were having oil consuption=20 problems with them. I think synthetic was keeping the piston rings from=20 breaking in so if you kept it in longer the oil would wear out enough to=20 allow the rings to start seating themselves. If you look it up I think=20 the oil change interval for C5 Vettes is 10k miles. So long as your=20 using the recommended synthetic oil that is. Personally I would run=20 conventional for the first 500 and 2500 miles for break in then switch=20 to synthetic.

The GM link referenced above says nothing about differences from division to division. I can imagine that the tuning of the system variables could well be different for different powertrains and/or vehicle types as each situation is different in it's oil wear out characteristics, but I doubt that GM's oil life monitor would be engineered differently by brand designator. I would bet big money that a Chevy Venture minivan would have the same oil life monitor system as does it's sister vehicle the Pontiac Montana. It has been many decades since the individual divisions of GM even had their own engineering staffs (though Cadillac is sort of getting one back now).

GM is doing a very good thing by giving a much more rational indication of when to change a vehicle's oil than can ever be achieved with simple minded distance/time recommendations.

John

Well, what works for me with Mobil1 is 10,000 km between changes. Seems the "oil life" monitor pretty much agrees. For me thats about a

50-50 mix of city/highway driving

Regards, Al.

"John Horner" wrote

Sorry, I disagree.....GM isn't trying to do anything good other then attempt to lull buyers into believing that their vehicles are "low maintenance" vehicles. Which will work fine for the lease type of buyer who basically blows off the car after 3 years. Any car will make it to 3 years and 60K klms with little or no maintenance. It's after that that the real problems with lack of maintenance start to show up. But does GM or the customer that unloaded the car after the lease was up care? No, why should they? They are no longer financially responsible for the car.

The more "rational" approach is to use a distance/time schedule. I see the results of "extended" oil change intervals every day.

Ian