Testing GM's Oil Life Monitor

[Scott P]

The wife's Envoy is a leased vehicle and according to the manual, I only need to change the oil when the OLM light turns on or after one year. Well, after 10 months and 10,000 miles the light still had not turned on. Since we will be driving to Houston in a few days (1,600 miles) while towing a small trailer, I thought an oil change was in order. I drained and sampled the 7 qts of Mobil 1 5W-30. I added LC at inconsistent intervals throughout the past few months. I've sent the sample off to Blackstone and am curious as to the result. Five qts of M1 SL and two quarts of pre-Katrina SM were added along with 4 ounces of LC. Maybe it will be another 10 or more months before the light comes on again. I guess I'll find out how good the OLM is. Any thoughts on how well the oil will fare?

 

[thooks]

I imagine the oil will be ok. I KNOW your fuel mileage will SUCK. Better be glad gas is $1+ cheaper. We had a Trailblazer EXT with the I-6 and the "change engine oil" light would come on about every 5,000 miles, even tho I'd change it at 3-3500k. I'll say since the engine bathes in 7 quarts of oil, you're ok. What year is this? I know the GMC's have a little more luxury items, but unless they've changed the monitoring system, I have a hard time believing the light has not come on. GM has measured the interval for a while by measuring RPM's.

 

[martyi]

Don't the GM OLMs have an oil life expectancy shown as a percentage? My Honda counts down the life of the oil based on percentages rather than an idiot light that comes on. When the oil life expectancy hits 15% a "service due" notice comes on. When it hits 0%, it says "service past due". I would think yours should work the same way.

 

[greenjp]

You're not really giving it a proper test, since you're using the LC. I have to assume that the OLM is designed with run of the mill dino oil in mind. jeff

 

[Triple_Se7en]

A better test would of been without the LC. I will never buy any 2-3 year-old GM vehicles because of this system/GM's asking to go by the idiot light. Anyone who plans on keeping their GM from birth until death should think twice before abiding by GM's wishes. Please! I don't need to hear replies about how well your GM is doing right now. Do that reply in 7-17 years if/when that vehicle gets old/beyond 300K. BTW... I am a multiple time GM purchaser. I ignore that system being a birth-to-death purchaser. As a matter of fact - with three "EXTENDED" oil changes thus far -- the light's never gone on.

 

[J. A. Rizzo]

With the LC added, your analysis results are pretty much useless. I wouldn't trust them at all for the purpose of judging the effectiveness of the Oil Life Monitor system. Furthermore, the LC may invalidate the effectiveness of the OLM for determining when to change your oil. You are adding factors to the equation that are not included in the OLM system. Why do you need the LC anyway? What is it gaining you? Especially in a leased vehicle, your oil maintenance practices are puzzling to me. TripleSe7en, why is the OLM so bad in your judgment? I know of maintenance-oblivious GM owners (1 truck, 3 different cars) who only change oil based on the OLM and regularly go 5000-10000 miles between changes and they have had zero lubrication-related issues on conventional motor oil in over 100k miles. I don't see why it's so bad. Looks to me like it works pretty darn well. Maintenance costs are reduced, the engines last just fine, less toxic stuff gets added to the environment, and owners know how to properly maintain their engine oil. Everything I read about it makes it sound like a well-engineered system with consideration for many factors that affect oil service life, and combined with the fact that I have never heard of anybody having oil-related engine problems while following the OLM, I can only conclude that the system is working well. Not many people keep their cars beyond 300k miles, and if they do, they've probably fixed so many other things that the replacement engine cost would have been a drop in the bucket. If there is a failure here, it may be that GM needs to set expectations about what to expect from your engine by following the OLM. You have presumed it will cause problems without any evidence of such, and I am assuming it won't cause any problems. You know my reasoning, and I'm interested in hearing yours. [ December 05, 2005, 05:03 PM: Message edited by: J. A. Rizzo ]

 

[yugrus]

"...the LC may invalidate the effectiveness of the OLM for determining when to change your oil." How come? The OLM does not do the oil analysis. It knows nothing about the oil you're using. It only has information on how the car has been driven.

 

[thooks]

J.A. Rizzo, As horribly over-priced as GM vehicles are, they SHOULD last without much maintenance. Their re-sale value sure doesn't.

 

[J. A. Rizzo]

Yugrus: "How come? The OLM does not do the oil analysis. It knows nothing about the oil you're using. It only has information on how the car has been driven." You are right and I agree. The LC invalidates the effectiveness of the OLM system because the engineers never accounted for LC being in the oil when they put together the parameters for the system. If LC actually does something to the oil, such as cleaning deposits from the engine, then those extra deposits in the oil were not accounted for when the OLM system was designed. No oil additives are required or recommended, and they weren't taken into account when the OLM was designed. If anything is added to the oil other than make-up oil, you are in uncharted territory with the OLM, and any oil analysis that is meant to judge the effectiveness of the OLM must abide by the parameters under which it was developed in order to be valid.

 

[yugrus]

J. A. Rizzo, thank you, I've got the point.

 

[Mighty HD]

I have 12,3xx on the GMC now, I reset it at the 4,000 mile oil change and it has not come on yet. I'm waiting to see how long it is before it comes on. Driving is short trips, and weekend drives, and 90% city driving. I'm a bit suprised with 8k+ on it.

 

[JohnnyG]

Please quote the year manufactured when discussing the GMOLM. My 2004 will come on every 12,500 mile without fail....and I have the oil analysis to prove that it is NOT doing any harm. It's posted here somewhere, no LC, no "synthetic", no makeup oil, no nothin' If you don't post year of manufacture, how else will we be able to tell if it's working?

 

[texasproud]

According to an ex-poster who was a GM engineer, the OLM runs on a sophisticated mathematical algorithm which takes into consideration, milage,cold starts, engine load, engine revolutions and probably some other things. It is calibrated for regular dino oil, and does not compensate for synthetic or oil additives.

 

[Mike_dup1]

From GM

quote:

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NOTE: Synthetic oil resists "wearing out" better than mineral oil, so the oil life monitor is set to account for this, but only on vehicles that are specified for synthetic oil from the factory -- the Corvette, for instance. Using synthetic oil in other vehicles is certainly not harmful, but the oil life monitor will continue to count down as though the engine contained mineral oil.

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GM cars that come with synthetic; Corvette GTO Several Cadillac models

 

[ekpolk]

Scott: Do you have the "% remaining" or the "change oil soon" light version of the OLM? Triple_Se7ve: The UOAs we've seen, and the articles published about the system would not seem to support your lack of faith in the system. On the other hand, since the OLM does not actually "examine" the oil itself in any way, it won't catch things like infamous GM coolant leaks killing the oil early. Do you have UOAs on your own vehicle showing oil exhaustion before the OLM calls for a change?

 

[Scott P]

I probably should have added the year and mileage in my original post. The truck is a 2004 with 21,400 vehicle miles.

 

[Cutehumor]

If some don't believe in the GM OLM, it doesn't hurt to go by it one time, use syn if your uncomfortable in the long interval, get a UOA. prepared to be converted

 

[Blue99]

Recently, the OLM came on at slightly over 8K miles, since the last reset, for my 2001 Sierra 4x4 with the 5.3L engine. I just reset it & will continue to stick with my separate, 4-5K OCI routine. For me, regardless of what the OLM indicates, 6K is the limit that I would run on GF-4/SM conventional oil. So, if I had the % remaining life feature, I’d consider changing the oil at the 30% OLM point. These GM V8's are strong engines, but have a tendency to generate combustion chamber deposits due to running at relatively low rpm's - 60 mph at 1500 rpm. Some of these components also makes it’s way into the crankcase via blowby gases. At 6K miles on conventional oil, I don’t expect an oil with a used up oxidative life to lubricate and carry a load of combustion insoluables.

 

[Blue99]

quote:

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...and I have the oil analysis to prove that it is NOT doing any harm.

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This UOA report? http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=3;t=002940;p=2 I think you failed to understand or ignored Terry Dyson’s comments. This oil sample showed high lead due to the corrosive effects of running an oil beyond the ability of the anti-oxidant additives to protect against the effects of fuel loading. The level of insoluables is a supporting factor. Suggest including a TBN and particle count next time a 12k OCI is posted to give a truer picture of the condition of the oil. The name of the game is not running a motor oil to the oil's physical limits - it's keeping a lubricating fluid, with fully functional additives, pumping thru the engine!

 

[Triple_Se7en]

No UOAs ekpolk! I've always been a premature oil changer. I'll typically run 3K dinos - 5K blends & a 7K Mobil-1 synthetic in the Colorado 4X4 with the OLM.