GM Mech. says "OLM not accurate"

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Smokescreen

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I brought our fleet truck in as it had a 'check engine' light on the display. Turns out the oil pressure sending unit is malfunctioning and threw a code. The 2012 Silverado only has 60K km or 37500 miles on it, meticulously maintained by the dealership and oil changed according to OLM. The dealership has never commented on our oil change regiment up to today.

Upon speaking with the GM Mech as I brought it in, he said that he is old school and doesn't listen to the OLM as it only takes into account outside temps and some MAF data. I let him know that it takes into account a bunch more data like engine speed, load etc and that it really is quite accurate,...he really didn't know anything about that. They have lots of those OPSU in inventory so it must be a flaky item. We are going to continue to use the OLM though.

I asked if it could be attributed to AFM cylinder deactivation, he said he didn't think so.

What are your thoughts on AFM shortening the OLM measurements? They must have accounted for that..right?
 
I'm sure they have. a few years back someone posted a link to an overview on the development of the GM OLM system - from someone involved in the development.
 
My OLM has been very accurate under a lot of different and severe conditions (lots of short trips, lots of towing, etc) for my 2012 5.3L. However, my only worry in the back of my mind questions whether there are other details not being captured by a UOA that might cause a problem later in life, like 100k+ miles.
 
The OLM has no clock.
It doesn't know what quality of oil/filter you are using.
The condition [wear] of the engine is not taken into account.

I still think it's a great system and I run my OLM down to negative 30 as UOA tell me it's okay to do so.
 
Originally Posted By: WobblyElvis

The condition [wear] of the engine is not taken into account.

I still think it's a great system and I run my OLM down to negative 30 as UOA tell me it's okay to do so.


Please note that the GM OLM setup is simply using data that they had been logging for years. Since it tracks so many parameters of the duty cycle to the detail of injector pulse width it does indeed factor in a lot that could be called compensation for wear.

It even accounts for stationary operation in our fleet PTO's!

OBDII systems have been compensating for engine wear for a long time...
 
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While it is fine being old school with some things, GM's OLM has been calibrated with many different variables to determine how long the oil will last in the engine. One mechanic or a team of scientists? The new OLM isn't just a timer.
 
OK, I have no problem with the OLM, I think its great. Just wondering considering they recalibrated for the direct infection engines...but I guess AFM has been around for over 5 years now so it should still be good.
 
If I had a car with an OLM I don't think I would use it. I'd probably still go by miles such as "7,500 or 10,000"
 
Originally Posted By: Nick1994
If I had a car with an OLM I don't think I would use it. I'd probably still go by miles such as "7,500 or 10,000"


Why use an arbitrary value with no data backing up when you would have a data based OLM?
 
A mechanic once told me to dump a quart of ATF in the gas tank to clean injectors. His theory was ATF is full of detergent.
laugh.gif
 
Originally Posted By: dishdude
A mechanic once told me to dump a quart of ATF in the gas tank to clean injectors. His theory was ATF is full of detergent.
laugh.gif


Find another mechanic
smile.gif
 
Originally Posted By: Nate1979
Originally Posted By: Nick1994
If I had a car with an OLM I don't think I would use it. I'd probably still go by miles such as "7,500 or 10,000"


Why use an arbitrary value with no data backing up when you would have a data based OLM?
Because I do UOA's
 
Very few dealer techs know anything about oil and the more seasoned they are, the less they know about oil.
A couple of years ago, I had a co-worker take his Ford car into the dealership because it had engine problems. When my co-worker stopped into the dealership that night, the most seasoned tech of them all asked if he used Valvoline in his engine. My co-worker said that he did indeed use Valvoline. The tech then berated him for using Valvoline because he claimed that Valvoline was the worst oil on the market and it caused sludge.
All that would make you think that the tech was super intelligent until you found all all the facts about all this. First, the co-worker had an oil change sticker on his windshield that said that his last oil change was done at a Valvoline quickie-lube place. (All the "tech" had to do was to look at his maintenance sticker to see that Valvoline was in the engine) Second, my co-worker seldom changes his oil and all the sludge in his engine was because he neglects most all maintenance on his car.
However, it sure made my co-worker hate Valvoline and he now admires his Ford tech more than ever.
 
The OLM in my Cruze (and all other 2011-mid 2013 Cruzes) is well-known to be an optimist. I change the oil at 7500 miles since that's when UOA's indicated that the off-the-shelf full syn oils I use need to be changed.

Our Honda's OLM is spot-on, and we run it down to the flashing wrench at 15%. IIRC a 10,000+ mile oil change was sort of scary the first time, but UOA's proved it could go even longer!
 
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Originally Posted By: sciphi
The OLM in my Cruze (and all other 2011-mid 2013 Cruzes) is well-known to be an optimist. I change the oil at 7500 miles since that's when UOA's indicated that the off-the-shelf full syn oils I use need to be changed.

Our Honda's OLM is spot-on, and we run it down to the flashing wrench at 15%. IIRC a 10,000+ mile oil change was sort of scary the first time, but UOA's proved it could go even longer!


yes, it is very platform specific. Just as Honda has it's VCM foibles that seem addressed by more frequent servicing, so too does GM have a few things going on with its smaller more modern engines. These small high output motors require close monitoring for optimal engine life.

But the V8's are spot on and yield extremely long engine life in our fleet use in a very tough duty cycle.
 
One thing the OLM cannot account for... atmospheric particulate matter... you know... dirt. When operating in very dusty conditions like the gravel roads that I have to go up an down for several miles, each way, to and from the house, daily. Especially in the fall like now, when a lot of semi trucks using the same gravel roads to haul harvest to the grain storage. I use the OLM on my 2013 as an additional tool to decide when to change oil, but no the only marker to go by. I guess I am in the middle. I don't fall into either side... that the OLM is as trustworthy as the sun coming up each day or that the OLM is unreliable. It is just another piece of information. But there are conditions where the OLM is not as accurate as some might contend.

Unfortunately, the OEM's have a lot of weaknesses in many of their design features when it comes to their pickups actually being used for more than grocery getters and taking kids to soccer games.
 
I don't trust the OLM (not to say I'm right or wrong, just my hard-headed opinion). The wife's Equinox had to be recalibrated because it was letting oil go too long. I change it anytime after 3,000 miles (2.4 D.I. engine). My pickup truck goes 3,500 + miles. Oil + new filter is cheap insurance. I'm an old timer so I couldn't even think about going 10K miles on an oil change. Too many variables like fuel dilution, dirt, etc. I use Shell conventional oil I get at the Costco.
 
Originally Posted By: Smokescreen
LOL

I brought our fleet truck in as it had a 'check engine' light on the display. Turns out the oil pressure sending unit is malfunctioning and threw a code. The 2012 Silverado only has 60K km or 37500 miles on it, meticulously maintained by the dealership and oil changed according to OLM. The dealership has never commented on our oil change regiment up to today.

Upon speaking with the GM Mech as I brought it in, he said that he is old school and doesn't listen to the OLM as it only takes into account outside temps and some MAF data. I let him know that it takes into account a bunch more data like engine speed, load etc and that it really is quite accurate,...he really didn't know anything about that. They have lots of those OPSU in inventory so it must be a flaky item. We are going to continue to use the OLM though.

I asked if it could be attributed to AFM cylinder deactivation, he said he didn't think so.

What are your thoughts on AFM shortening the OLM measurements? They must have accounted for that..right?
Garbage in garbage out. Who really knows except GM and it takes a lawsuit to get any truth out of them.
 
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