oil life system

txg · January 24, 2002

I have a decent background in organic chemisry and I always find it interesting to read everyone's opinion on oil change intervals. Attached is a really good article about GM's oil life system, it seems to be fairly accurate.

Please post your opinions on why you do or do not use the system that is on the newer trucks.

As I said, understanding the chemistry of how carbon chains breakdown, I have always thought that the magic 3,000 mile interval was ridiculus and I plan on letting the Oil Life system tell me when to change my oil

Oil Life System

chevy4x4trucks · January 24, 2002

I do mine every 2500 miles and it's usually pretty close to when the indicator goes off. I do mainly city driving, and the bulk of my driving is to and from work which is 2.2 miles from my house and there's about 4 stop lights and 3 stop signs on the way there. After reading the article I feel more confident that I'm not really jumping the gun on it considering the weather conditions and my driving habits.

Good article though, it's good to know how the system actually works.

bassdog · January 24, 2002

Please post your opinions on why you do or do not use the system that is on the newer trucks.

I don't have a new style truck, and in turn have nothing but my own piece of mind to tell me when to change my oil.

I am one of those who change every 3000 miles due to short trips. I only drive about 20 miles a day...less than 3000 every 3 months.

If I had an on board computer to tell me it's ok, and GM backing that up, I might consider it...

bassdog

CityTruck · January 24, 2002

Hmmm. I planned on changing mine every 3K. I've always done this with every car/truck I've owned (except my wife's which seems to reach 3 months before 3K miles so it get's changed more often). I'm not sure what to think about this article. I actually recycle glass, plastic, cans, bottles, etc and try to do my part to protect the environment so my daughter will have a nice place to raise her kids and so on, but I'm buying a V8 truck too so I'm not a complete tree-hugger. I've always considered my religious addiction to changing the oil every 3k was just another way to "baby" my vehicle. I'm going to have a hard time giving that up. Plus, I generally use synthetic so I'm not depleting resources as such though I realize it's still a polution issue.

GreenRado · January 24, 2002

Interesting article. Makes me wonder why I change my Mobil1 so often now!

I had what was probably an earlier version of this system on my '88 Calais, and it seemed to be similar, in that it took into account the driving conditions, at least, not just mileage. I always ended up changing the oil (usually every 4000 miles) and life left usuall read ~ 50%. The truck system seems closer to what I actually do - perhaps because it is more local stop and go trips than the Calais was (lots of highway miles).

My only sticking issue w/ extended oil changes, regardless of dino or synth oil is when is the oil filter effectiveness decreased enough to justify a change, even if the oil is still "OK"?

01z71 · January 24, 2002

Good Article. I don't think I'll change my 3,000 oil / filter change schedule though.

Ed Hahn · January 24, 2002

I have a decent background in organic chemisry and I always find it interesting to read everyone's opinion on oil change intervals. Attached is a really good article about GM's oil life system, it seems to be fairly accurate.

Thanks for posting this. It certainly helps me plan my oil change strategy on the K1500 Avalanche I picked up last Friday.

Given this information, I will probably follow the oil life system recommendations, using synthetic oil (since I will be towing a >5000lb trailer several times a year).

From your estimation, any idea on whether the oil life system also takes into account engine load in addition to revs, or does that make any difference at all?

ed

txg · January 24, 2002

I don't think that engine load is relevant because the engine puts out a certain amount of power at any given rpm, a higher "load" would cause the engine to work harder by having to stay at a higher rpm and the computer accounts for this.

NewbieZ71 · January 24, 2002

I let mine go once to see how long.....gave up at 4600 miles...just too long for me...change my synth at 3000 plus or minus and still havent seen the change oil light...

timfarn · January 25, 2002

I drive mostly highway miles and I'll go about 5,000 miles with the 5.3. I still track the oil life monitor - it has gone off at 6-7,000 miles. I've done extended changes (up to 7,500) on our '96 Bonneville. It now has 185,000 and uses less oil than it did at 100,000.

sierra1 · January 25, 2002

On my last oil change at 3000, I was pulling into the dealer's driveway, and the oil change light comes on. A couple of weks ago, I just had it done, and I was pulling out, and it went on. It was 3015 miles since the last one! They had forgotten to reset it.

I have always tried to not go much further than 3k, a guy I lived next door two had a 427 Impala, dont remember what year(68?), and he changed his oil every three months in the summer, and changed it every two in cold weather. I was about 16 and to make some extra money, I helped him change the oil pan, it had been hit by a hunk of steel on the road and had a hole in it. It had about 100K on it, and I had seen old motors before, but this one was so clean inside I couldn't believe it! Later on, I helped with replacing the rear seal on an old Nova that had been running Mobil 1 since it came out. He changed it every 4 months. It had about 60K on it, and it looked great in there too.

I figure it doesn't cost that much to do it right...even if it is slightly overkill

GSXER2 · January 25, 2002

I have kept track of mileage and change intervals since new.During to warmer months I tend to do more distance driving so the mileage between these intervals has been about 25% more than in colder months.My driving habits in winter are mostly short trips and shut down is when engine temperature barley reaches 140 degrees.I need a change now and my last change was mid August. Winter change interval is about 4200 miles summer change interval is 5600 miles.Maybe the system is a good thing for me.

Ed Hahn · January 25, 2002

I don't think that engine load is relevant because the engine puts out a certain amount of power at any given rpm, a higher "load" would cause the engine to work harder by having to stay at a higher rpm and the computer accounts for this.

If the engine always put out the same amount of power at a given RPM, then the engine would always accelerate until it blew itself up (or hit the rev limiter).

Put it another way, say you're cruising down a flat highway at 55 mph in top gear, and the engine turns about 2000 rpm (roughly - exact number isn't important for this). Assuming your torque converter is locked up, then it is a simple matter of transmission gear ratios and tire size which fixes this speed/rpm relationship in a given gear. (That is, 55mph always equals 2000 rpm in top gear).

If the truck is always putting out the same power at this rpm, then you couldn't mash on the throttle and accelerate (otherwise, where is the extra power coming from at the instant you hit the throttle, which allows both the engine and vehicle to accelerate?)

Simiarly, you couldn't let off the throttle and coast down either (otherwise, where is the extra engine power being diverted to that would allow the truck to slow down?)

Finally, imagine that a 5000lb trailer suddenly appeared hitched up to your vehicle while moving down the highway - where is the extra power coming from to overcome the additional rolling resistance and aerodynamic drag?

OTOH, I can buy an argument that a higher load means a high oil temp, which will then be accounted for by the computer.

siume99 · January 25, 2002

I think the last paragraph sums it up the best:

"From these studies and other subsequent investigations it is clear that there are distinct benefits to drivers of vehicles equipped with the oil-life monitoring systems. For those who neglect to change their oil on a regular basis, the system provides reminders that a change is due. If they need the reminder and follow through with an oil change, they'll protect their engine from premature wear. And, drivers who thought they needed to get their oil changed every 3,000 miles (5,000 km) or so, might be able to go longer between changes. This will save them money, time, and perhaps more importantly, precious natural resources. "

I think the important points are to help remind the absent minded and at the same time try to limit the use of natural resourses. IMO Changing the oil 3K or sooner doesn't hurt the engine one bit (less abrasives in the oil). However, it will hurt your wallet, natural resources, and finding the time in the day for the 20 min procedure.

ED Could you say your idea in another way? I'm a little confused by it. ???

Ed Hahn · January 25, 2002

ED Could you say your idea in another way? I'm a little confused by it. ???

Sure - sorry about that.

According to the (admittedly simplified) description of the oil life system in the article, it only measures two things: temperature and engine revs.

I was wondering whether it made any sense to also measure engine load (e.g. throttle position or some such) and also factor it in, so it can tell the difference between say, towing a heavy trailer in the winter vs. normal driving in the summer.

The engine oil temp might be the same for both situations, but the load on the engine sure isn't.

ed