GM OLM observations

[HondaMan]

Let me add my observations from Texas:

(08 Silverado 5.3L J Vin Iron Block Non-Flex)

For the first 6k miles.... it would take days and weeks to drop off even a single % tick. I think I was at 6k miles and 40% OLM.

No introduce the colder weather here in Texas (nothing like you guys are seeing up North) ..... and suddenly one or two % points in a single day ...

What I was assuming is that there was a weighted penalty for the longer duration AND the cold start.

BUT what you guys are reporting is that even on new 100% OLM fills... the cold starts are penalized very heavily. Very interesting

I'd say that is good, very good.

As others stated... if the OLM after 2k miles says to change it... change it.... You'll get your full return on your motor oil from the OLM in the summer, when like mine, the OLM barely gone down to 40% with 6k miles.

I'm down to 20% btw... with 6.8k miles. I've dumped the oil three times now as I am following a specific break in plan, but after this last fill, I will use full syn. and simply follow the OLM.

 

[demarpaint]

Wow that's an eye opener for those of us who don't have an OLM. There are times when one or more of my fleet sees that kind of service. Some of us would say a 3000 mile OC even with dino is a waste, but based on the OLM readings I see here a 3000 mile OCI is to long for those conditions.

Frank D

 

[brianl703]

Originally Posted By: Drew99GT
Makes me wonder why they went with a 4 quart sump on an engine almost twice as big as the Ecotec.


You may or may not have seen the oil change interval formula, that takes into account sump size, fuel economy, horsepower, and displacement. It's been posted on here a few times.

I plugged the numbers from my 1988 Ford Mustang GT (5.0L V8 with 5 quart sump) and my 1996 Ford Contour (2.5L V6 with a 6 quart sump) and came up with intervals within a few hundred miles of each other. I think I posted the results of those calculations on here somewhere, too.

I also plugged the numbers from a 1993 Ford Escort (1.9L I4 with 4 quart sump) and came up with an interval within a few hundred miles of the other two.

As far as the OLM goes, my Saab 93 has an OLM and it definitely decrements slower during highway driving than it does for cold start short trip service.

 

[crinkles]

i wish aussie cars had an OLM... I'd love it. My trips are mostly 2 mile trips one way 4 times a day from cold. the minimum temps here are generally between 10 and 20 deg C though so it is not in freezing conditions. I have settled on a 5,000 mile / 7,500 km OCI but I can't be sure.

 

[HTSS_TR]

Your owner manual may have shorter OCI for severe driving conditions, you may have to change your oil and filter based on time rather mileage.

 

[Nyquist]

I just changed the oil in my fiance's Cobalt with the 2.2L Ecotec. There was still 70% on the OLM, but with the extreme cold we've had lately, there was a ton of moisture on the oil cap since she likes to leave it idle a lot. I don't know if mine is a bit off or not, but I'll trust my instincts more than the OLM.

 

[RoGuE]

In my Malibu 2.2L Ecotec, I changed the oil February 26,2008 and it is only at 37% now. I am using Pennzoil Platinum 5w-30. Our climate varies a lot. 2 days ago the high was in the mid 70s, today the high was about 36. This past summer was VERY hot and humid, with many days over 100. I will probably be changing it out around January. I would love to get a UOA, but I can't really afford it, or justify it right now (although I did get a kit in case I changed my mind)

Edit: I forgot to mention the the current oil fill has 3627 miles on it since I changed it. I don't drive very much, I drive relatively short trips which is 4 miles each way to work, stopping at about 2 stoplights each way, and sitting in traffic. Takes me about 15 minutes to go that 4 miles). And commuting to college 5 days a week is about 7 miles each way on curvy, hilly roads and takes about 9 minutes each way.

 

[HTSS_TR]

Originally Posted By: Drew99GT
... My mom drives about 4 miles to work everyday, and to the grocery store and to run errands several times a week. The shopping center/grocery store is about .5 miles away. Every cold start on this interval has been below 20 degrees, with most being on average 10 degrees.


For this kind of driving conditions, I would use the thinnest dino and change according to OLM.

 

[GMBoy]

Originally Posted By: zulu
Dunno. GM has always had somewhat undersized sumps compared to the rest of the world.

Heck, my Silverado only holds 6 quarts. 1 extra quart over the Ecotec, and more than double the displacement. Go figure...


I'm not sure about that now as times are changing. I had a 2001 Olds Aurora with the 4.0V8 that held nearly 7qts, my 2008 Cadillac CTS holds just over 6qts. But, yeah the older V8's are smaller. My 94 Corvette holds 4.5, same with my 87 Buick Grand National.

 

[Benzadmiral]

Over the 16 months I've had my Buick, I tend to drive the same paths at the same time of day and at the same speeds, five days a week. With that boring but consistent scenario, the OLM has consistently reported oil life dropping by approximately 12 - 13 % a month (for example, I'm a little over two months and 1950 miles into the current oil change, and the OLM reads 73 %).

 

[3putter]

Undersized GM sumps ??

My Buick Lucerne with the Northstar V8 has a 7.5 quart sump.

 

[zulu]

That makes sense that the Northstar sump is so big. GM set the max mileage between OCIs at 12,500. I wondered why they made such a huge interval, but now I see.

Most all of GMs older 4 cyl were only 4 quarts. Lots of the V6s are still under 5 quarts. I guess there are exceptions, but it seems that the engineers who calibrated the OLM definately took that into consideration.

 

[3putter]

Good observation. My OLM took me out to 12,000 this last OCI. Lot's of hwy miles.