Tahoe OLM question

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Falcon_LS

Falcon_LS

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A buddy of mine has a '07 Tahoe Z71 and covers about 30,000 km (18,750 miles) of driving per year. Having read a lot about the GM OLM here, I've forwarded the links to him and he's convinced that he should be resetting it at each oil change and following its advice on when to change the oil.

We changed the oil in March, using Motorcraft Syn Blend 10w30 and an AC PF48 filter. The OLM was reset and the oil now has 25,000 km (15,625 miles) on it. According to the OLM, oil life is at 12%.

I'm kind of worried having ran 25,000 km on a synthetic blend, and I'm pushing for an oil change. He just wants to keep driving until the "Change Oil Soon" warning comes up. Question is, should an exception be made or should he just keep driving on it until the OLM deems its time for a change? This is getting scary. Thanks!
 
Well, there is a UOA on this site of a guy with a Silverado truck that ran his OLM to 0%, and that was 12,650 miles on pre-DS Havoline 5w30.

Wear was okay, and TBN was 1.6, so technically, the oil 'survived', but that's about it. In a warm climate, with mostly long-distance driving, I could see an OLM going very, very far.

GM put a lot of work and research into it's OLM, so your buddies engine will be just fine. But if you do a UOA of the oil, it will be right at the end of it's life.
 
He actually has quite a commute, and works 6 days a week. So his weekly mileage is 1,500 km (938 miles). Would using cruise control very regularly have an affect on the OLM?
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If he's driving long distances at a very steady highway speed, that's the easiest you can be on an oil, so yes, it would make the OLM 'count down' very slowly.
 
Most of the commuting miles are hollow miles. No fuel enrichment ..little filter loading. You're into other fatigue factors that most of us never allow to come to bear. He's operating under ideal conditions.

He's got a one year limit to the OLM's indicated %.
 
Keep in mind that the OEM recommendation w/o the OLM is an averaged/managed fudge factor. It's the limits of how they can express the conditions that one will encounter over (for example) 7500/6months. You would probably have no trouble doing 3m/3k for a delivery vehicle ..yet the vehicle may process as much or more fuel (do more work) than a 7500 mile vehicle over 6 months.

It's mainly perception. It's like filter life. It's mainly dictated by how many cold starts it sees. That's why the upper mileage end can be quite long. The intermediate miles ..those between cold starts are pretty much empty as far as it's concerned. Any alleged metal particles it's seeing ..at least in terms of measured wear ..are pretty much not being produced to near the level that they were in cold start (20 minutes) ..and they may or may not even be filtered to begin with.
 
Gary, you're a smart guy and I usually agree with almost everything you say. This, however, doesn't fix a nervous breakdown.
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This is a perfect example of why I do not trust OLM's. I am no expert but it sounds like there is something wrong with your OLM.
 
I can see GM's OLM going that long under *ideal* conditions with a 6.1 quart capacity. If you're worried about it just put in a higher quality oil made for extended drains like EP.
 
Not that I'm aware of. The only situation where it could be a problem would be if there was some air filtration/air plumbing leak ..an internal coolant leak ..or some fuel issue like leaking injectors. Outside of the coolant leak I would think that this would be factored in. These items can and do cause elevated wear, but it's unlikely that they'll really shorten the life of the engine. The OLM is determining the suitability of the oil. There will be hundreds of thousands of units that can and will have the same plumbing leaks ..and will be equally ignorant of them.

It's just calculating the limits of the oil to protect the engine.

If you think about it, I'd say that an air filtration leak is only read in the oil on the secondary level. The primary damaged material gets blown out the exhaust.
 
Originally Posted By: webfors
Right, the OLM assumes everything is in working order, to summarize Gary
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An assumption is only as good as the facts backing it. To my mind there are many more good facts behind the decisions of the GM OLM than the blind OCI. The 3/5/7.5/10/25k OCI ALSO blithely assumes that your 3.1's LIM hasn't washed out.
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Hi,
calvin1 - You said this;
"An assumption is only as good as the facts backing it. To my mind there are many more good facts behind the decisions of the GM OLM than the blind OCI. The 3/5/7.5/10/25k OCI ALSO blithely assumes that your 3.1's LIM hasn't washed out."

Well said - IME such an instrument is one of the best ever installed on a motor vehicle. The more sophisticated of these devices will enable a greater use WW of a very valuable resource - oil! It encourages far less pollution too!!!
 
Originally Posted By: Gary Allan
Most of the commuting miles are hollow miles. No fuel enrichment ..little filter loading. You're into other fatigue factors that most of us never allow to come to bear. He's operating under ideal conditions.

He's got a one year limit to the OLM's indicated %.


Agree 100%

Plus he gets to be in a nice warm weather which pre-warms the oil.

Perfect conditions for motor operation. The only thing there would be the dust/dirt so air filter would be VERY important.

So like Gary said, OLM or 1 year whichever comes first.
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Bill
 
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Yes. The OLM is equally as ignorant of physical conditions as the 3k/3m ...as M1's EP 15k figure ..as Amsoil's ONE YEAR deal.

It's really a blissful state (imagine tweet-tweet sounds in the background)
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My Gm OLM's were accurate in that with city driving it would hit 15% at about 5500 miles. When I would drive to Florida and back on vacation (4000 miles mostly freeway) it would drop about 20%. I once drove from Key West to Akron non stop (except gas) and in 1400 miles it dropped 8%. But since most of my driving was stop n go I would do a 5000-6000 OCI.
 
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