Oil Life

[TenGHz]

What do our cars use to determine remaining oil life?

[harofreak00]

In all internal combustion engines, the primary driver in oil degradation is the combustion event. Every time the engine fires, a small volume of oil is directly exposed to, and destroyed by, this high-temperature, high-pressure event. Furthermore, combustion gases containing acids, fuel, and water get past the piston rings and react with, and degrade the engine oil. In addition to the combustion event, oil temperature plays a role in oil degradation. As oil temperature increases the oxidation rate of the oil speeds up, which can lead to oil thickening over time. On the other hand, colder oil temperatures increase the concentration of contaminants, such as fuel and water in the oil. The GM Oil Life System comprehends these oil degradation processes, and using an algorithm, calculates the optimal time to change the engine oil. While the basic algorithm is the same for all GM engines, each engine gets its own calibration specifically tailored to its unique needs.

http://www.gm.com/corporate/responsibil ... 040104.jsp

[bonnevillain]

sounds all well and good, but keep in mind

[/quote]Since the GM Oil Life System does not actually sense oil condition, it is important that the engine computer knows when an oil change takes place. By enabling the reset (read owner's manual for instructions), it lets the computer know an oil change has taken place.[/quote]

I doubt it's as sophisticated as they make it sound... wonder if any of this could be looked at in the PCM? doubt it. anyways..

I change it when it gets to 5k no matter what the oil monitor says (or sooner if the monitor says, although that hasn't happened)

[TenGHz]

It sounds like it just calculates temperature and RPM's and pretty much guesses.

I was curious because my scanguage can read oil life, and was wondering where that percentage came from.

I assume that if you don't do the reset procedure the car would never know when you change the oil...

[brandonb4322]

General rule of thumb is to change your oil every 3000 miles or 3 months(Whichever comes first). Oil breaks down chemically into a goo(sludge) alot quicker than alot of people think and depending on your driving habits it could even be sooner than 3000 miles.

[thunderhand]

is it the same for synthetic as for dino ??

does dino break down faster ??

[Jim W]

I think the OLM only considers the oil that went into the car from the factory (most likely dino). For cars that have higher quality like Mobil1 from the factory, the OLM is calibrated as such.

/assumptions

[lunchboxx]

I was under the impression that with synthetic oils, the frequency of changing could be extended ( for normal conditions) to twice a year. I dont remember where I read it, but I remember reading that the old standby of 3 months 3000 miles was far too soon...at least for synthetics. not sure about the dino oil. However, if you can afford it, I couldnt see what it could hurt to change it more often, but I have other things I like to waste my money on...

[lewis26]

My dad has worked for BP Amoco for 28 years, and knows all about the technology in motor oils. He has continuously said that synthetics can be used for 10k miles, if not more. They do not break down anywhere close to as quick as conventional oil does. I try to go with ever 6k miles, sometimes 8k depending on the oil life monitor.

[its840]

iirc the oil life thingie on the dash was based off milage.. cause mine would always go off at 6k miles... i have always ran synthetic oils... and i try to change ever 6k miles.. however there have been times where it has gotten as high as 8k.. but i always run mobile 1 oil... check advance auto (pdq) in your area.. they had a sale last weekend for 5 qrts of mobile one oil and a mobile one oil filter for 26$.. wahoo.. should have grabed 2 of them...

[skregal]

I have been an Amoco dealer for 19 years and "yes" the synthetics are great and long-lasting from a lubrication standpoint, however they get just as dirty, and most people do not upgrade to a better filter to last the extra miles.
If you use a synth for twice the mileage, you should use a high grade filter like Wix.

[lewis26]

I have always used mobile 1 filters in my cars, not the cheapo ones put in by oil change places.

[LeSabre in Buffalo]

It depends on the amount of wear metals in the oil.

Pretty much any of today's SM grade dino juice can go 4-5k miles without batting an eyelash. Synthetics can go even longer. I've seen analyses of 10k mile synthetic oil changes that look absolutely pristine.

For filters, Wal-Mart SuperTech is much superior to Fram. Better design, better filtration, and cheaper. I personally use a Wix because it's an extra $2 and it's a bomb-proof filter. Even the AC Delco filters are okay for 5-7k miles.

[00Beast]

Amsoil has a reccomended oil change interval of 25k miles, if used with their oil filter and Engine Flush on your first fill. They also offer Engine analysis, and that will tell you how good your engine is on the inside, where it matters.

[lewis26]

The days of oil changes every 3k miles are over. Synthetic oils are just that good. Unless your engine is putting an excessive amount of metal into the oil, synthetics will last incredible amounts of time, with little degradation.

[wjcollier07]

My last change on the truck had me at 2% on the Oil Life Monitor...8,529 miles, 5 months. Always a PureONE filter. (Synthetics, while good, are only as good as your filter) Always Mobil1 for me. Color was dark, for sure, but proudly I can say that at 47k, 1700 hours, the engine didn't need one bit of touch up for the whole 8500 miles. I probably should have sent that in to be analyzed. Definitely doing it next time.

93 goes by mileage, 6-8k on Mobil1 and a PureONE. First change was M1 5W-30 on Sep 20, 2007 @ 95k, and the next was same oil and filter on June 20, 2008 @ 102,500. That was a little long since the car doesn't get driven all that much anymore. Since I left it, 11 months, 20 days ago, it has only seen probably 5k. As of today, only has 104,353. Because of that, the changes will probably be more like every year, or 6k, whichever comes first.

[00ssei]

Ok i have a question. Ppl seem to either use fully synthetic or conventional oil. I use the Mobil Clean 5000. Using that, should i change it every 5000k or 3000k?

[wjcollier07]

5k miles is fine with the right filter. However, I wouldn't recommend 5 million miles as you stated

The filter is always the most important part about extending drain intervals. Even cheap conventional oils still have to meet certain standards. If oil were always clean, it wouldn't need to be changed. Obviously, with conventional filtering methods, that isn't possible, but it is getting close.

I would say that 5000 miles would be permittable with most conventional oils, with a filter like a WIX, Amsoil Ea or Purolator PureONE.

Honestly, I don't like middle ground oils..it's kind of like Plus grade gasoline...it sorta is unnecessary...and is really only a blending of the premium and the regular anyways.

Stick with a good conventional oil like Pennzoil, Castrol GTX, etc and a good filter, or go with Mobil1 and a good filter and change it every 6k or so.

[00ssei]

I used the Mobile Clean 5000 with a regular filter that they provided. I know it was the cheap ones so, should i change it after 5000 or 3000 since i used a wacky filter?

What I've heard is that you should change the oil the same as your previous owner. For example, if my previous owner used conventional oil and i start using Fully synthetic, ive learned that that is bad or vice versa. ANyways, thats why im using mobil clean 5000 because its not bad or good oil.

[wjcollier07]

3000 miles on a crappy filter max.

It is true you shouldn't switch back and forth often, but you CAN switch it to your preference.

My 93 ran conventional oil until 95k, I changed it to M1 and a PureONE, after using some flushing crap in there, to clean out any crud, and almost immediately, some leaks started, but after a little while, about 1,000 miles I'd say, the leaks stopped completely once the crud was out of the way, and the seals re-hydrated and went back into place. That's my speculation on it, but it did stop. It lost about 1 qt in the first 3000 miles, and then after that, didn't lose a drop. So far, it is about 2000 miles on its second oil change of M1 and a PureONE under my ownership and it so far hasn't lost any oil at all.