GM Owners: GM Oil Life System -vs- Self Directed Mileage for OCI ?

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Nov 23, 2004
River Falls, WI
I own two new motors, both of which contain the GM Oil Life system.

Those of you guys that own a GM vehicle with the OLM system, do you rely on it to tell you when to change your oil, or simply pick a mileage .....i.e. 3K, 5K, 7.5K, 10K etc.
If you have some way to view the actual percentage of oil life remaining, it can be useful to see how severe the computer thinks the service is by noting how many miles it takes to drop 1%..and you can use that information to pick your OCI if you think the computer's calculated OCI is too long.

If you just have the light which goes on when it reaches 0%, that's not so useful.
I dont use it because I have no way of knowing what % my oil life is at in my camaro. So, I do a 3k Oil change because I drive 6mi round trip each day to school and back, maybe Ill go on a 10-15mi jaunt if I get a chance. My oil life monitor tends to kick the light on around 5500-6000mi under these conditions which is insane! The range of my monitor is 3000-7500. So I really wonder what on earth I would need to do to make it come on sooner. In my opinon the light is a worst case scenario light.
All it costs is one LED and a couple minute circuit board traces in actual materials.

The rest is programmed into the ECM; so to get the "true cost" one has to spread an engineer's salary out over all the cars covered. I'd rather have them working on something like that instead of more plastic junk tacked on to pontiac fenders.
I change it at 6 mos. Have never had the OLM come on in either of two vehicles. This is the best approach using dino IMO. If you use full syn you should probably go one year.
come on guys, Use the OLM. run the best syn you can find, go by the light. the GM OLM was calibrated for dino. so if you use the light and use syn, you know you would have plenty of life left without UOA.
I'm going to go into this a bit because my new Honda has an OLM similar (I guess) to GMs. It calculates engine factors such as load, revolutions, temps, etc. as well as miles driven and makes assumptions as to oil life expectancy. I read somewhere where it also "penalizes" you for things like short trip driving, thereby reducing the percentage of oil life expectancy.

Most owners of this vehicle (Ridgeline) who have had it long enough to go through a service due notice say that the notice comes on when the oil is at 15%. This seems to occur anywhere between 5,000 and 7,000 miles, depending on driving habits. This contraption is suppose to be so accurate that all service is tied into the monitoring system, even tire rotation notices.

In fact, there is no OCI specified in the manual. It says change oil only when the OLM tells you to or, if you do not drive enough miles for the notice to ever come on, change oil once a year, whichever comes first. There are some notes if I recall about dusty or other "severe" conditions but I'm not certain if those notes applied to the oil (I'm not where I can get my hands on the manual right now).

There are some things the OLM can not know that would impact on OCIs besides "severe" conditions. For example, how does it know if you are using synthetic which should last longer than the dino the OLM is calibrated for? How does it know if you are topping off which will rejuvenate the oil somewhat? Ditto if you are using a product like LC20.

But those factors aside, it seems to me that changing oil (under most normal driving conditions) by this sophisticated software is the best way to go for both protection and conservation, not to mention the money that will be saved as (usually) the OLM extends OCIs beyond the point most people traditionally have gone.

The other option of X number of miles and/or X number of months is old, old thinking and totally arbitrary. I'm not saying that experience should not come into play here as I use to change oil every 5,000 miles no matter what and never had a problem in 40 years of driving cars. But engines have changed and oil has changed, technology has changed, everything has changed! And usually for the better.

I am sold on the OLM concept and I intend to follow it religiously unless I suspect a problem. I know for a fact I'm not as smart about these engines as the Honda engineers that designed and built them so I'll do what they tell me until someone can prove they are wrong.

Having said all this, since this is my first OLM equipped vehicle, I will do periodic UOAs over the years just to be sure this thing is always calibrated and working properly and telling me the truth about my oil and engine.
I actually go longer than my OLM tells me. My oil life monitor in my 98 Corvette is set up based on a 10k interval, which is what the 97-00 Corvettes had, but in 2001 they changed it to 15k.

So the 97-00 OLM is too conservative. You could really reset it at 0 and go another 50%.

Good points, I have an Odyessy van with the OLM. I think you have a little more trust in it than I do.

I would feel a lot better if Honda, GM, and the other OLM's released the "intellgence" built into these system so we could determine just how sophisticated it is. Predicably, however, they don't say much other than "trust us". That's fine, but remember this is a car company, and ultimately they want your car to wear out so you buy another one. This is also a company that offers a rather stingy 36k engine warranty (I believe they did change this for 06 of course).

I too will be running syn and getting UOA's done to see if I can stretch to the full OLM recommendation for my wife's rather brutal short-trip, traffic-clogged driving. At the first sign of oil being iffy I will revert to shorter changes.

Call me crazy, but 6k+ on ruthless short trip, high-idle time driving still gives me the willies.
I have a 2005 Pontiac G6 with 5000 miles. So far I've changed the oil twice with the monitor showing 70% and 63% left. I'm not going to trust the OLM. I have been using Havoline 5-30 with an STP filter. If I go to Mobile 1, and for whatever reason want to go back to Havoline, Can I do that? Switch from synthetic back to regular oil?
Merlin64 - You are correct about the warranty. The 2006 Ridgeline came out well before their other new models (I bought mine in May) and all they had was their traditional 36K bumper to bumper warranty. However, I received a new warranty book the other day that extends the powertrain warranty to 60K to coincide with the other 2006 models. So, that was very nice to hear. The new warranty is not bumper to bumper of course but covers all components of the powertrain.

If you want to learn a bit more about background and thinking that went into the OLM's development you can start here: GM OLM

Scary - I think it is always a good idea to stick with one kind of oil, even one brand if you can. But I do not think switching back and forth between dino and synthetic will do damage.

[ November 14, 2005, 01:17 PM: Message edited by: 59 Vetteman ]
We have seen several examples of where the OLM does seem to work. Someone had a "Soccer Mom" cousin who drove mostly short trips in town and whose OLM indicated very short OCIs. We have seen examples of the OLM indicating a long OCI for a 5.3L engine that had mostly highway miles (this is the engine that had 12K using Havoline dino with great results).

There are several good threads about the OLM and the science behind it. I have a 5.3L Tahoe and have changed the oil between 4-6K miles since new, but I am going to let it run for at least 9-10K miles this OCI. I just put M1EP 10W30 in the Tahoe and I am going to extend the OCI. I drive mostly highway so I expect the OLM to give me a long OCI. I might do one shorter OCI (7K) for this first switch to M1EP, but then I am going to extend and get a Dyson UOA. I will post the results.

I think the OLM is useful and I am going to try using it. It is difficult to break the habit of 5K OCIs.
Both my Saturn SL1 and Silverado have the OLM but I haven't relied on them YET.

My recent UOA on my Saturn has me convinced to go out at least to 5k on it this time (which is a big step for someone who WAS a 3k person!)

Pennzoil Platinum (with LC) is in it now, and if the UOA looks good on it at 5k, then I will probably take it out per the OLM the next time. The truck gets about 2 oil changes a year with the miles it gets so I really don't worry about that one.

I do wish that my vehicles had the display that told me the remaining life on the oil like some of the newer ones do.
I use the OLM on both of my GM vehicles. On my 2000 Monte, it typically gives me 5 - 6k miles. I'm not sure about the '05 Terazza yet, but expect 7 - 8k miles. Given I use M1, I'm perfectly comfortable with these intervals.
I agree with using the OLM but as a 3K OCI person for the past 30 years, I am struggling ...

I have just rolled over 6K on this oil Dino Castrol GTX with an AC-Delco filter....pressure is good, motor is quite, level is full, with just a slight carmel color, 2 0z of ARx maintenance, new motor with 12000 K on a 4.8L 04' Tahoe.

All is well, but again I am struggling to be patient and see how it goes...I am 90% highway 40 miles each way to work....very little the motor reaches temperature and cruise at a steady 65....
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