Oil Life % vs. Reality

fleishman · #1 (**permalink**) 09-21-07, 03:20 PM

Hello everyone,

I typically change my 97 SLS's oil when the % meter gets down to less than 10%, mostly because I don't want to reset it and forget to change the oil and if I don't reset it the chime bugs the heck out of me..

I have never kept track of how many miles in-between oil changes. The oil is always rather dirty and in need of changing.

How does that meter calculate the % left? Oil temp + miles + average speed + anything else?

So heres my question:

If I am adding about a quart every 1000 miles, and I don't happen to mention it to the car, how accurate is that oil life % if I have been mixing in fresh oil?

Let me know how often you folks change your oil.. Thanks!

JimD · #2 (**permalink**) 09-21-07, 07:00 PM

Quote:

Originally Posted by fleishman

....
I have never kept track of how many miles in-between oil changes.

I do and my average oil change interval is 6,670 miles. '98 Seville at 159K miles.

Quote:

How does that meter calculate the % left? Oil temp + miles + average speed + anything else?

All those plus more. The OLM system developed by GM was exhaustively tested and verified by oil analysis for each engine that uses it. The system is so unique (and trustworthy) it earned a patent. There is a built in safety factor of 100% - even if you do not have to add fresh oil several times between changes.

**Ranger** · #3 (**permalink**) 09-21-07, 07:39 PM

Jim pretty much said it all. It uses more things to calculate than I can remember. Engine temp, RPM, ambient temp, throttle position (load) and much much more. Bottom line is that it knows if it is summer or winter, if you are a grandma or a hot rodder, if it is a to the corner store trip or an interstate road trip, if it is city drive or highway driven. Trust it. It is smarter than you (we) are.

submariner409 · #4 (**permalink**) 09-21-07, 08:13 PM

I believe the OLM and find that it keeps pretty good track of how I drive in any given month. BUT, as one who grew up on "Kendall, the 2,000 mile oil" (the 2-fingered fist logo), it tries my soul to go past 6 months or so on the same oil. Sooooo, to be honest, I change oil and filter nowhere near as often as in the past, but whenever I get antsy. That works out to every 8-10 months. And, by appearance, the oil doesn't need changing then, mileage notwithstanding..........Modern engines and lubricants are incredible........

**Ranger** · #5 (**permalink**) 09-21-07, 09:48 PM

Old habits die hard Submariner. We graduated from the same school. Took a long time to convince me.

AJxtcman · #6 (**permalink**) 09-22-07, 05:42 PM

Look over here at this.
http://www.cadillacforums.com/forums...ml#post1225099 (Oil Life Monitor -- How Does It Know?)

wydopnthrtl · #7 (**permalink**) 09-25-07, 11:00 AM

Excellent reads.

I use full synthetic Mobil 1 and spray nitrous a few times a year. Otherwise we put about 20k easy miles on the car per year. (at 71k now)

I'm anal about noises and such and one thing I've clearly noticed is that when I get into the 50%-40% & below area the motor will make more noises when fully warmed. It'll do this as well after a long road trip. I'm not sure what's going on with the oil but I've switched to 10w-30 mobil 1 and change it at about the 50% mark which keeps the motor as quiet as can be. (keep in mind.. I'm just anal about things like piston slap and such. 99.9% of people would never pay the attention to it that I do)

Rich

fleishman · #8 (**permalink**) 09-25-07, 12:27 PM

Ok, great info everyone, but the GM OLS, as far as I see, does not know about the fresh oil poured in every 1000 miles and is basing the oil life on the original 7 quarts and its life expectancy. Unless the pcm is taking things like viscosity, flow rates and density into account I dont see how it could adapt to know that over the approx. 7000 miles between changes, that I have put 7 quarts of oil in already..

What are your oppinions about using a synthetic oil on a car that has always run non-synthetic, like the high milage plus oils? If my year was not designed for synthetic and how durrable it is, then wouldnt the OLS be off?

**Ranger** · #9 (**permalink**) 09-25-07, 01:00 PM

No, the OLM does not know that you have added a fresh qt. every 1000 miles. That is just added insurance.

You can use synthetic or high mileage oil if you want. Won't be a problem. Remember, there is about a 100% safety margin built in to it.

submariner409 · #10 (**permalink**) 09-25-07, 04:08 PM

Engines are not specifically designed for base petroleum vs. synthetic petroleum oils. The manufacturers recommend synthetics when there is chance of extended hard driving and high performance use. As in Corvette, Ferrari, and Lamborghini, to name-drop a few. (Synthetics are generally petroleum oil stocks which have "had their DNA altered" by extensive processing.) You could build a '49 Ford flathead and run it forever on synthetics.

Tommy Deville · #11 (**permalink**) 09-26-07, 07:28 PM

excellent read, I fall into that severe driving short trip range, I get between 3 to 4k out of my oil b4 it tells me 2 change it.
When I did more Highway drivving & longer trips I would get about 6 to 7,500k between oil changes.
No matter how much driving I do or don't do I always wind up putting 1 to 2 quoarts of oil inbetween changes