GM Oil Life Monitor

Joined
Jul 21, 2008
Messages
328
Location
Pennsylvania
My grandmother has a '98 Buick Century 3.1 V6. I changed the oil in it a year ago(Pennzoil YB and Pure One) and haven't touched it since other than checking the oil level. I only change the oil once a year because the car only goes to the supermarket on Fridays and church on Sundays. The car is lucky if it sees 1k per year. She called me yesterday and told me that the "Change Oil Soon" light had come on. Could it be that all the short trips are being hard on the oil and that is why the light has suddenly come on? I've heard that the lights have a habit of coming on early. Any help would be appreciated.
 
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If the trips to church and the supermarket are only a mile or so, then it's definitely possible. I've heard of the OLM coming on after 2k under severe service, so depending on the type of service, it isn't out of the question.
 
Joined
Feb 5, 2008
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texas
my wife used to have an OLM on her chevy (98)and it would vary a lot so I pretty much just stuck with the OCI's I was used to. If you are using a recommended oil, filter and air filter then you should be ok. I would still keep an eye on miles to see if here is a pattern.
 
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Washington St.
Did you reset her car's Oil Life Monitor each time you changed the oil? The reset method varies by car model...check her owner's manual.
 
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Apr 18, 2008
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Kentucky
I have a 2008 Silverado pickup with the OLM that tells the percentage of oil life remaining. I have changed the oil 3 times since I bought the truck in April of 2008 and the OLM still says 33% oil life left. I am just going to let it run to see how far it goes until it gets to about 10%. I don't guess I have to say that I have absolutely no trust in it whatsoever, but that is just me.
 

Bill in Utah

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Nov 11, 2002
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Yes the OLM is very accurate. My Aunt has a Impala with the V6 and hers has gone off in about 2,500 miles and 8 months. She drives it so little and now that she takes the bus everywhere, I'm trying to get her to sell me the car for my soon to be 16 year old Daughter. Every UOA seems to show the OLM to be very good. I'd trust one without question. I wish every engine had one. Take care, bill
 
Joined
May 27, 2003
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1,565
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Elkridge, MD
I've been following it in my '06 Monte Carlo. So far it's instructed me to change the oil at 6,789, 7,109, 8,203, and 7,463 mile intervals. I also jumped the gun on the 6,789-mile interval, changing it at 8% remaining when on the others I let it go to about 5%, and on the 8,203 mile interval I let it go to 1%. I collected a sample for a UOA a while back but never sent it in. From all I've heard, I'm not worried about it in the least. I use M1 or M1 EP (only because it was on sale) and M1 filters, FWIW.
 
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Aug 15, 2006
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Central Washington
Im going to go by the OLM on my grandparents 2001 Pontiac Montana. They put 4000 on this change so far and it appears to be setting them up for a 5000-5500 interval. I have Pennzoil HM 5W30 and a oversize WIX-made ACDelco PF52 in it,.
 
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Aug 8, 2008
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Cali
 Originally Posted By: FrankN4
I have a 2008 Silverado pickup with the OLM that tells the percentage of oil life remaining. I have changed the oil 3 times since I bought the truck in April of 2008 and the OLM still says 33% oil life left. I am just going to let it run to see how far it goes until it gets to about 10%. I don't guess I have to say that I have absolutely no trust in it whatsoever, but that is just me.
I have an 08 Malibu LTZ and don't go by the OLM either
 
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Apr 4, 2009
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Southeastern, PA
I have an '06 Chevy Impala. I reset the OLM after I change the oil, but I tend to change the oil every 3500-4000 miles regardless of what the OLM indicates. Usually the OLM says 30% life remaining when I change the oil at 3500-4000 miles. The OLM supposedly uses a very good algorithm to determine oil life, but I am not sure it is absolutely trustworthy. I may just request a free kit from Blackstone and pay for a UOA the next time I drop the oil. Then I will know if I should just go by the OLM and save myself time and money on oil changes. The car is no longer under warranty, and GM says that even while under warranty the OLM is fine to use. My most recent Onstar report shows my current oil life at 74% and my next maintenance due at 43,600 miles. The oil was last changed at 37,500 miles and I am now at 39,400. I plan on changing the oil at 41,000 miles, which will be a 3,500 mile OCI. The OLM, if the warning comes on at 43,600 would be a 6,000 mile OCI. I guess that is not too bad. I use conventional Mobil Clean 5000 5W30 oil and an AC Delco filter. $15 total at Walmart :)
 
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Joined
Jun 5, 2008
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Location
Lancaster, PA
Are GM oil life monitors calibrated for the type of oil they recommend in the manual? For example. My TransAm has an OLM (just the dash dummy light) and the manual recommends just regular dino oil. So that means if I use synthetic, the OLM isn't accurate anymore and I should go by UOA's. Right?
 
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Sep 25, 2006
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 Originally Posted By: MiniTransAm
Are GM oil life monitors calibrated for the type of oil they recommend in the manual? For example. My TransAm has an OLM (just the dash dummy light) and the manual recommends just regular dino oil. So that means if I use synthetic, the OLM isn't accurate anymore and I should go by UOA's. Right?
Most people feel if your vehicle was "calibrated" for dino oil - then synthetic will give you just a little extra margin of protection. Personally I tend to agree. I myself go by the OLM on my Chevy SUV. I've tried various oils, and I think my vehicle runs just as good if not better on dino. Nothing scientific here - just butt dino results! :) I'm not saying you are wrong - if you want to run it a little longer than the OLM states AND you have the UOA to back it up (this assumes the vehicle is not under any type of warranty)then I don't see a problem with it. To other posters who are skeptical about the accuracy of the OLM - many people have done UOAs and found the OLM to be RIGHT ON THE MONEY! Plus I know various people who have over 150K miles on their GM engine - using the OLM. Some at trailvoy.com go as much as 12K miles OCI (remember the I6 engine in Trailblazers holds 7 quarts of oil). The only engine failures we've seen are caused by neglect - as in running the engine 3 - 6 quarts low on oil! People mistakenly believe that the OLM monitors their oil level so they don't bother checking it. That just isn't true!
 
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Joined
Jul 7, 2008
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CA
 Originally Posted By: MiniTransAm
Are GM oil life monitors calibrated for the type of oil they recommend in the manual? For example. My TransAm has an OLM (just the dash dummy light) and the manual recommends just regular dino oil. So that means if I use synthetic, the OLM isn't accurate anymore and I should go by UOA's. Right?
Yes. They're calibrated for the factory fill. If you go synthetic you must get a UOA with TBN to find an accurate OCI.
 
Joined
Sep 26, 2007
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Midwest
I'd have to say that in general the OLM is very accurate. On my 03 Buick it used to come on about every 3,500mi with a mix of city/hwy 40/60% respectively. Now that I'm doing 98% of my driving in highway miles, it doesn't come on for at least 5500mi. I'm at 6200 for this oil change and it has yet to come on.
 
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May 28, 2007
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earth
I wish my car had one. I feel that australian cars are going to be along time behind the US just as OBD-II isn't compulsory here (Toyota format on my camry is not obd-II but OEM specific) If I had one, that would be great, I'd run M1 to 0% life remaining.
 
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Nov 17, 2002
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fyi Oil Life Monitor -- How Does It Know? How long will oil last in an engine? What reduces the oil’s effectiveness? When should it be changed? Lubrication engineers perform a number of tests to answer these kinds of questions. Vehicles are operated under prescribed conditions, and periodically a sample of the oil is taken into the laboratory for analysis. When the condition of the oil is no longer satisfactory, the mileage is noted. From controlled testing like this, engineers in the past have determined two sets of mileage numbers, one number for normal driving and the other for severe conditions. Severe conditions can mean that the vehicle is driven hot (for example, pulling a trailer up a mountain) or is driven such that the oil never warms completely (for example, trips less than 5 or 10 miles in a winter climate). It is then up to the owner to decide whether their own driving is normal or severe and to change the oil accordingly. Now, science and technology have found a way of taking the guesswork out of the picture. GM is installing an oil life monitor in an increasing number of new vehicles. Using a simple indicator lamp or readout on the instrument panel, this system notifies the driver when to change the oil. The February and March 2000 issues of TechLink explain how to reset these monitors. Here’s information on how an oil life monitor works. Additives Straight oil is not an ideal lubricant in an engine. A package of additives is needed to give the oil properties it does not naturally have or to enhance its natural properties. Some of the tasks accomplished by additives: - viscosity modifiers, to keep the oil the proper thickness over a wide range of operating temperatures - anti-oxidant, to keep the oil from thickening - corrosion inhibitors, to protect engine components - anti-wear - anti-foam - detergents, to suspend solid particles. What Makes Oil "Wear Out?" If you were to start out with a crankcase full of fresh, clean oil, and drove the vehicle for a period of time, eventually the oil would have to be changed. During this time, what can change fresh oil into "worn out" oil? First, dilution. When gasoline is burned in the combustion chamber, the by-products include a lot of water. Some of this water can find its way into the crankcase through piston ring blow-by. If the engine is cold, and if combustion is not perfectly complete, a small amount of acid is formed. It, too, can blow-by into the oil. You don’t need to be a top-notch scientist to realize that water and acid aren’t good things to pump through the lubrication system of the engine. If an engine is run long enough for the engine oil to warm, the water and acids will evaporate and not accumulate. But, during very short trips in cold weather, water and acids can enter the engine oil and cause the oil to "wear out." Second, the degradation of the oil and its additives. We mentioned earlier that a number of additives are put into oil to improve its performance. If these additives are degraded or decomposed, the oil is no longer capable of doing all of its jobs properly. Oil with degraded additives can become thick and dark. Additives become degraded by exposure to extreme heat. There are two places a lot of heat can reach the oil. One is near the combustion chamber. Oil at the top piston ring is exposed to very high temperature. And some bearing surfaces can also put a lot of heat into the oil at high operating temperatures. So, degradation of additives from high temperature operation is the second factor that can cause oil to "wear out." How Can Operating Conditions be Used to Predict Oil Life? Using carefully controlled laboratory tests, it’s possible for lubrication engineers to measure how long it takes to dilute engine oil during cold operation. And it’s possible to measure how long it takes for high temperature to degrade the additives. We usually think of measuring time in hours and minutes, but for an engine, the amount of revolutions it has run is also a good measure. So for the purposes of oil life, time is measured in engine revolutions. Engineers like to talk in terms of models. A model is a way to describe something mathematically. It’s possible to create an oil life model that very carefully matches the results of analyzing the oil in a laboratory. The oil life monitor, then, is based on a model. A computer chip in the Powertrain Control Module is loaded with a certain number of engine revolution counts. The count for each engine/vehicle combination is determined by testing. As the engine runs, each revolution is subtracted from the remaining count in the oil life monitor. When the count reaches zero, the instrument panel light comes on. But, here’s the clever part. When the various input sensors detect that the engine is running under either cold or hot conditions, it subtracts extra counts (penalties) for each engine revolution. So, the conditions that cause the oil to "wear out" make the counter run down faster. When the oil is changed, it’s necessary to reset the oil life monitor (see the February and March 2000 issues of TechLink) and the countdown begins again. 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. - Shirley Schwartz contributed to this article
 
Joined
Oct 12, 2005
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Da Swamp
My OLM was at 33% remaining when I had the oil swapped Friday at 6 months/4800 miles, and I drive about 75% city. If the monitor is as accurate as many here are saying, I could have gone another 2400 miles, almost 9 months total, before zeroing out and requiring a change.
 
Joined
May 1, 2006
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New Brunswick, Canada
I'd love to know where this thought that if you use synthetic oil you can run longer OCI's came from. To my knowledge only 2 brands have ever claimed this. The engine doesn't realize you spending more money on your oil and automatically start burning cleaner to save you money. Synthetic oils don't suffer from thermal break down as easily in most cases but additive package still gets contaminated at the same rate. Where synthetics can excel is in artic temperatures flow rates & thermal breakdown in desert temps. Trying to get longer drain intervals out of you oil, will, in the end, cause increased engine wear, so in the end you're not saving anything. If your intentions were to not get the most out of your vehicle, then you wouldn't spend the difference on a better oil in the first place. Follow the manufactures guidelines for date & mileage. A so far as GM's OLM I find it's set a little long for my tastes.
 
Joined
Dec 10, 2002
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USA
The OLM is great technology. I would run full syn and run the OLM down to 0%. As documented, most OLM vehicles are designed to run on dino except the vette and most cadys. So if you run the OLM to 0% at 9000 miles oci and have full syn. I wouldn't sweat it at all.
 
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