OLM confused???

[oldhp]

2012 Equinox 2.4 with fresh FRAM XG9018 oil filter, 5qts Mobil1 5w30. Drove to Florida and back, 2000 miles. OLM was at 100% at start and now shows 78%. Of those 2000 miles only 90'ish were in town driving at Florida for 5 days. I thought highway driving was easy on oil and OLM readings. Your thoughts.

 

[Warstud]

Sounds about right. For every 20% your getting 2000 miles of driving. So 0% would be 10,000 miles.

 

[cmhj]

Dont see a problem

 

[WobblyElvis]

I recently went for a 3,500 mile road trip. %98 highway. OLM on my Malibu went from 100 down to %52. You are doing fine. It doesn't know what oil or filter you are using. I take mine down to minus 50 then change oil and filter. UOA says there is still life left in the oil.

 

[ExMachina]

oldhp and WobblyElvis, Those GM OLMs put a penalty on high-rpm driving. Since you both sound like you're running GM 4-cylinder DI engines on the highway, and I'm assuming you were really moving fast, those 4 cylinders can hit the high-revs often. I got a look at the GM OLM algorithm the other day and noticed that it counts engine revs, and the penalties are severe for cold driving and/or high rpm driving. Of course the cold driving accounts for water getting into the oil, and the high speed driving accounts for blow-by getting higher and pressures-temperatures breaking apart the oil more. .... You get the least penalty for cruising at about 55 mph steady in top gear.

 

[CELICA_XX]

We had the same car (GMC Terrain) and if I remember correctly, it would subtract 1% per 61 miles regardless of how the car was driven.

All city stop & go driving with two hours of idling per day was the same as a road trip with 100% easy highway miles. It made no sense to me.

But that car was a piece of garbage and changing the oil was the least of my worries. After 70,000 miles and three transmissions... we were done with it.

 

[Merkava_4]

I don't see the problem either. . . change out the oil. . . how cheap can you get ?

 

[oldhp]

ExMachina, Didn't know that about counting engine revs, never thought of it that way. I just didn't think it would use 22% on only 2000'ish highway miles. Well now the poor thing will go back to short, short trips. I'll run it another 2 months and change it.

 

[ExMachina]

oldhp, the GM OLM algorithm is described in https://etda.libraries.psu.edu/paper/9507/5943
if you do want to read about it. It counts engine revolutions, then counts every revolution worse for oil life that is in a cold engine, or when that revolution is at high load and high rpm, like when towing a trailer up a hill for a while will be a penalty, and you're also putting a lot of revolutions per minute at once. So, yeah, easy cruising between say, 50 to 65 mph with few hills to make the torque loading (cylinder pressure) go up is the easiest on oil. Sort of complicated algorithm, and pretty accurate.

Notice the OLM doesn't know if you're using a better oil, like a fully synthetic over an oil that just barely passes the dexos1 performance specs (semi-synthetics). So if you're using a full syn, I'd guess the OLM is too conservative by around 25%.
If you're using the full syn Mobil1, then that OLM will get to zero% and you will technically have some life left in the oil. So zero% is good with Mobil1.

 

[CKN]

The OLM is smarter than most owners....

 

[bvance554]

Down to 78% in 2000 miles sounds normal to me. I'd change according to the OLM, and not a guy on a forum 'guessing' you could go further on his favorite brand of oil.

 

[Quattro Pete]

Originally Posted By: oldhp
2012 Equinox 2.4 with fresh FRAM XG9018 oil filter, 5qts Mobil1 5w30. Drove to Florida and back, 2000 miles. OLM was at 100% at start and now shows 78%. Of those 2000 miles only 90'ish were in town driving at Florida for 5 days. I thought highway driving was easy on oil and OLM readings. Your thoughts.

If you extrapolate linearly, that would give you about 9,000 mile OCI. The OLM does not know that you're running synthetic oil. It is calibrated for mineral, or maybe syn-blend oil at best (if it requires Dexos1 oil).

 

[Benzadmiral]

Originally Posted By: ExMachina
oldhp and WobblyElvis, Those GM OLMs put a penalty on high-rpm driving. Since you both sound like you're running GM 4-cylinder DI engines on the highway, and I'm assuming you were really moving fast, those 4 cylinders can hit the high-revs often. I got a look at the GM OLM algorithm the other day and noticed that it counts engine revs, and the penalties are severe for cold driving and/or high rpm driving. Of course the cold driving accounts for water getting into the oil, and the high speed driving accounts for blow-by getting higher and pressures-temperatures breaking apart the oil more. .... You get the least penalty for cruising at about 55 mph steady in top gear.

That explains my swift drop in the OLM for my Regal, which has the same engine. I thought I would see little drop on my 2000-mile highway trip to Amarillo last year, but it fell about the same as if I'd driven normally (70% city) for 2 months -- during which I'd usually drive, you guessed it, 2000 miles.

As Celica_XX put it, "We had the same car (GMC Terrain) and if I remember correctly, it would subtract 1% per 61 miles regardless of how the car was driven." That's pretty much what I see.

 

[WobblyElvis]

My Malibu is an 06 with a 2.2 engine. It's not DI, nor does it have variable valve timing. The OLM normally allows me to go from 5,500 miles in winter to about 8,500 of summer driving. I was very surprised that on the latest trip with almost constant 70mph cruise and only stopping for 10 minutes every 2 hours, the OLM was counting down to hit zero at about 7,500 miles. IMO constant highway driving would not wear the oil out that fast.

I recently had a recall performed on the car and perhaps they recalibrated the OLM. I usually change oil after running the OLM down to minus 50. UOA says the oil is fine.

 

[Greasymechtech]

http://autoweek.com/article/car-news/gm-reprogram-some-oil-life-monitors

As long as all recalls are done, run with it!