: Oil change



Luna.
09-08-05, 06:31 PM
Are most people waiting until the GM Oil Life System (GMOLS) tells you to change the oil or are some still operating under the "every 3,000 miles" adage??

benjet
09-08-05, 06:54 PM
GMOLS only, there is NO NEED for any more frequent changes (other than during break in), period.

rand49er
09-08-05, 07:04 PM
What does the GMOLS "sense" anyway? Oil viscosity breakdown? ... acidity (pH)? ... various other contaminants? ... metal particles? I guess I'm still old school until I understand it better, so I did first one at 1.5k, second at 4.9k, and third at 8.2k.

RobzBLKV
09-08-05, 07:07 PM
I really don't think there was ever an adage of "every 3000 miles" for synthetic oil. I was planning on about 7500 miles this go around and I think that would hit right about when the sensor indicated it was time. I will draw a sample and send it for analysis to make sure it's not hurting the engine, though.

DILLIGAF
09-08-05, 07:08 PM
When my oil pct is less than 40% I start freaken out.It just doesn't seem right to leave oil in that long,so I change it.And then I use the old oil in the lawn mowers and the golf cart.Makes me feel a little better about spending so much money on oil.

benjet
09-08-05, 07:26 PM
I have done a full oil analysis after every oil change in my V. I've gone 10k, then 8k between changes based on GMOLS, and the oil was still good enough to be put BACK into the V for many more miles. Someone (anyone) please tell me factually why I should change it any sooner.

http://www.cadillacfaq.com/faq/answers/oilmon.html

Luna.
09-08-05, 07:33 PM
What does the GMOLS "sense" anyway? Oil viscosity breakdown? ... acidity (pH)? ... various other contaminants? ... metal particles? I guess I'm still old school until I understand it better, so I did first one at 1.5k, second at 4.9k, and third at 8.2k.

From the FAQ:

How the Oil Life System Works

We’ve explained the GM Oil Life System (GMOLS) in detail before (March 2000, May 2003) so this is going to be brief.
GMOLS is a computer-based algorithm that assesses engine combustion events, temperature, vehicle use, and other parameters to determine optimum oil change intervals. Oil changes are now called for when actually needed, instead of depending on generic time or mileage interval tables. Mild highway driving in a mild climate can yield change intervals of 7,000 miles (11,000 km) or more, and as high as 12,000 miles (19,000 km) for some vehicles. Short trip driving in cold weather may reduce intervals to 3,000 miles (5,000 km) or less. Most people driving a combination of city and highway will likely see intervals of about 6,000 miles (10,000 km).

When GMOLS determines that an oil and filter change is needed, the driver is notified by a Change Oil message on the instrument panel (fig. 10). Oil should be changed within 600 miles (1000 km).

TIP:The Oil Life System must be manually reset when the oil is changed.

How the Oil Life System is Related to Maintenance
The previously complicated, traditional normal/severe maintenance schedules required about 25 pages of explanation in the owner’s manual. The new simplified maintenance schedules can be explained in about 3 pages (see TechLink May 2003 for a summary).

All routine maintenance is grouped into one of two schedules, Maintenance I and Maintenance II. These services should be performed alternately, each time the GMOLS message is displayed.

Benefits of GM Oil Life System and Simplified Maintenance
Benefits for the customer -- GMOLS takes the guesswork out of when oil changes are needed; the owner doesn’t have to keep track of anything. With maintenance intervals now aligned with oil changes, the customer can conveniently have both done during one service visit.

Benefits for the dealer
Because of the typically extended oil change intervals, the customer may come back less frequently. But when they do come back, it’s for more services. The inspection and service points of both Maintenance I and Maintenance II are thorough, and are intended to keep the vehicle in good working order. They also give the technician the opportunity to locate, identify and recommend other needed services.

Benefits for the environment
With GMOLS now installed on upwards of 20 million vehicles, if it’s used as intended, it can save almost 100 million gallons of oil in 5 years. And remember that every quart of oil poured into an engine eventually has to be drained out and properly disposed of.

EDIT--lol--sorry Benjet--didn't see your post until after I posted this. :)

rand49er
09-08-05, 09:49 PM
Thanks, Luna ... very informative. But, I feel so-o-o good after I change it! :) Now, I won't get that feeling as often. :banghead:

BTW, every drop of oil out of my vehicles, boat, lawn tractor, etc. is recycled (i.e. re-refined), but I get your point. The data base used predicts the need to change the oil and sounds fairly inclusive of those variables which are important to the integrity of oil in an internal combustion engine. Thanks, again ... it makes sense, now. :worship:

benjet
09-08-05, 10:09 PM
I should add that after 10k my oil life was reading 0% for about a week. After the 8k it was 1% when I changed my oil.

Luna.
09-09-05, 02:22 AM
Thanks, Luna ... very informative. But, I feel so-o-o good after I change it! :) Now, I won't get that feeling as often. :banghead:

BTW, every drop of oil out of my vehicles, boat, lawn tractor, etc. is recycled (i.e. re-refined), but I get your point. The data base used predicts the need to change the oil and sounds fairly inclusive of those variables which are important to the integrity of oil in an internal combustion engine. Thanks, again ... it makes sense, now. :worship:

LOL. I wasn't suggesting anything either way. I was just curious as to whom changes their oil more often then the GMOLS suggests, as I like to change my oil quite often as well. :D

From the comments that Benjet is making, however, it sounds like it's not that unreasonable at all to let GMOLS tell you when to change your oil.

That's what I was planning to do in the first place, but any hesitation is now gone based on Benjet's comments.

ctsvett
09-09-05, 02:24 AM
I change it no longer than when the GMOLS reads 50% (which is usually about 3-5k miles.


Reed

Luna.
09-09-05, 02:26 AM
I change it no longer than when the GMOLS reads 50% (which is usually about 3-5k miles.

Reed

Interesting.

Why is that?

Dave's V
09-09-05, 02:42 AM
I change mine every 6000 miles because I believe it is cheap insurance. Yeah, the warranty will cover and engine problem (maybe) but it would likely occur after the warranty. I don't worry when I'm going up 10% grades in 110 degree heat fpr thosands of feet in elevation change. My oil temp never went above 220, water around 198. Even if the shop does it $50 a month is cheap insurance every 6,000 miles. I'm more worried about the oil filter also if I kept the oil in longer.

PneuBird
09-09-05, 03:57 AM
I have no qualified data to suggest that frequent oil changes keep the engine cleaner; but considering we have a larger capacity oil pan on the "V", I for one worry about the contaminets in that tiny oil filter we have. Anytime a 50% reading pops up, it's oil and filter change time in my book. I plan on keeping this set of "cubes" for a lomg time!! :thepan:

ctsvett
09-09-05, 04:15 AM
I actually let mine go a little farther last time... Somewhere (dont remember where, sorry) but there was some data that showed the mobile one got better with age (apparently its like a fine wine- BLITZER- HAHA!)...

Let contaminents and better properties around the 3-5 k mark...

If someone is so inclinded and recalls (and find) that data, we can reopen the discussion on that..

Personally though, I wont let it run below 50% again.... It IS cheap insurance.

Reed

Barak
09-09-05, 12:56 PM
The engine isn't such a determining factor in vehicle life anymore. The engine will go 200K+ miles even if you changed the oil every 15K. By that time everything else on the car has fallen apart and it's ready for the crusher anyway. So why bother changing it so often, especially when oil analysis shows that at 10K miles the oil is still good. It's a huge waste of time and money.

RobzBLKV
09-09-05, 02:19 PM
Oil analysis doesn't lie. While I intend to prove it to myself again with this oil change, I have never had an analysis that said 3k was necessary with synthetic oil. Changing as often as I used to is a huge waste of money, imo.

BeagleBrains
09-09-05, 02:40 PM
I for one worry about the contaminets in that tiny oil filter we have. Anytime a 50% reading pops up, it's oil and filter change time in my book. I plan on keeping this set of "cubes" for a lomg time!! :thepan:
There was an excellent thread addressing the oil filtering capability of various filters. http://www.ntpog.org/reviews/filters/filters.shtml
http://www.knfilters.com/oilfilter.htm
OEM Filters are usually 60-100 micron filters. After market, such as K&N are 10 micron particulate filters. AMSOIL has a parallel filter setup where a bleedoff line on the main filter bypasses a small portion of oil to a one micron filter, which is said to extend oil life and help remove contimanents. I agree, contaminents cannot be prevented. Their accumulation degrades the lubrication capability, regardless of the long term quality of any oil. I choose to go for engine longevity, changing at 300 mile intervals. I use a racing filter from Cantron. They have various filtration capabilities. Don't go too fine, as this will increase the differential pressure across the filter and reduce the required oil pressure and flow through engine components.

Barak
09-09-05, 07:49 PM
I choose to go for engine longevity, changing at 300 mile intervals.

I think you're supposed to check the oil at every fill up, not change it.:histeric:Your engine will last no longer than mine by changing your oil every 3000 miles. Don't get me wrong, I change my oil once a year whether it needs it or not.:D

BeagleBrains
09-11-05, 12:46 PM
I think you're supposed to check the oil at every fill up, not change it.:histeric:Your engine will last no longer than mine by changing your oil every 3000 miles. Don't get me wrong, I change my oil once a year whether it needs it or not.:D
Now that is rediculous. :tisk: I change oil at 3000 (Three thousand) miles. Thanks for the wakeup check.

SoFlaV
09-12-05, 12:43 AM
When I was grabbing coffee and a bagel this morning, ran into an owner of a 2002 Aston Martin Vanquish. Out of curiosity, I asked him about how the maintenance was on a car like that; my service center wouldn't touch something that high-end. He said the first synthetic oil change on his car hit him for $650.00; of course, that was also at 10,000 miles.

As for me, I get twitchy at 50%. Mine is due mostly to the first oil change I had done after I bought it, when there was a chunk of metal hanging off the drain plug. Since then, though, the changes have been clean. Maybe it was just the break-in period.

a64pilot
09-12-05, 08:30 AM
The GMOLS is an excellent system. If your car is close to stock, you should use it. However there are at least two things it cannot know of. Calender time and ops in dusty environments. So you need to watch those.
My opinion is to run the Syn oil until the car say's change it and use the money you save and buy a good oil filter, I.E. Mobil one or K&N. If you really want to take good care of it and are the type that will keep your car until the wheels fall off. Then invest in a bypass oil filteration system like Amsoil. Either way the syn oil is not what usually drives oil change intervals, it's the accumulation of contaminants.

Dooman
09-12-05, 09:21 AM
I think the 3000 mile change was invented by the Jiffy Lube business. They scared you in to thinking you MUST do it..

Koooop
09-12-05, 02:23 PM
The engine isn't such a determining factor in vehicle life anymore. The engine will go 200K+ miles even if you changed the oil every 15K. By that time everything else on the car has fallen apart and it's ready for the crusher anyway. So why bother changing it so often, especially when oil analysis shows that at 10K miles the oil is still good. It's a huge waste of time and money.

I change the oil in my Vette every 7,000 - 10,000 miles, the engines go a couple of hundred thousand then the head go, usually the exhaust valve seat shoot out the tail pipes. I won't own the V long enough to find out about wear.

BeagleBrains
09-12-05, 09:05 PM
I bought my first car in 1958, a 1950 Hudson. My first new car, a Corvair, in 1959. Learned about being a car fanatic from my father. Replace distributor cap, spark plugs, wires and such at two years. If a vehicle I own reaches 6-7 years of age, I replace all consumables: Belts, hoses, oil and brake rubber connections, suspension rubber (now to synthetics); oil pump, fuel pump, fuel injectors. My last Jeep Wrangler, which I owned for 13 years, went through this regimen twice. This Jeep endured my ownership over the long hall because of numerous modifications and customizing. This very personalized vehicle became my favorite toy. Sold for 50% above average resale value. I have not been concerned about longevity of ownership because I buy a new car fairly frequently. Married 38 years, have owned 25 new cars and 8 new Jeeps; normally one car and one Jeep at any one time; each accumulating 6-8000 miles per year. However, I change oil and filter at 2500-to-3000 miles. I won't own the V that long, but, engine care, as I see it, is the point of this thread.

Barak
09-12-05, 09:40 PM
I have not been concerned about longevity of ownership because I buy a new car fairly frequently....However, I change oil and filter at 2500-to-3000 miles.

So you admit that you are completely brainwashed by Jiffy Lube. :cookoo:

Dennisscars
09-12-05, 10:35 PM
I change the oil in my Vette every 7,000 - 10,000 miles, the engines go a couple of hundred thousand then the head go, usually the exhaust valve seat shoot out the tail pipes. I won't own the V long enough to find out about wear.

I agree with koop, if your not going to keep forever, go a long on the oil. Why spend money for the next guy?

a64pilot
09-13-05, 08:25 AM
I agree with koop, if your not going to keep forever, go a long on the oil. Why spend money for the next guy?
The point is that you don't have to change oil at 3000 anymore even if you want to keep it forever. With lean burn engines and unleaded fuel to say nothing of synthetic oils, the rules have changed. Look at how long the plugs last now. That's a direct comparison of how the leaner burn and unleaded fuel have changed things

globed70
09-13-05, 10:32 AM
Amazing how most of the population is happy to eat and drink chemicals, live on an improper diet, get too little sleep, slug a few too many beers...
But heaven forbid us letting our precious cars have a few too many particles in the oil.

Dennisscars
09-13-05, 11:18 AM
The point is that you don't have to change oil at 3000 anymore even if you want to keep it forever. With lean burn engines and unleaded fuel to say nothing of synthetic oils, the rules have changed. Look at how long the plugs last now. That's a direct comparison of how the leaner burn and unleaded fuel have changed things
:yeah:

tedcmiller
09-14-05, 10:46 AM
Back before synthetic oil became common, Consumer Reports ran a test on two fleets of NYC taxicabs where identical engines were run for 60,000 miles. In one fleet, the oil was changed every 3000 miles and in the other fleet, every 6000 miles. At the end of the test all the engines were disassembled and critical parameters (bearing wear, etc.) measured. They could find no significant difference in the wear on the engines. Changing oil, synthetic or not, before the OL indicator goes to 0% is a waste of time and money.

benjet
09-14-05, 04:56 PM
Still no FACTUAL evedence to support changing oil @ 3k or anything below GMOLS recommendation, until then everything else in this thread is BS.

I have factual evidence (yes for my V) that GMOLS is correct.

99m3
09-14-05, 07:20 PM
How much us an oil change for the V anyway? I'm at 36% and my oil low light just came on so I'm taking it in for an oil change.

SoFlaV
09-14-05, 08:18 PM
How much us an oil change for the V anyway? I'm at 36% and my oil low light just came on so I'm taking it in for an oil change.

My Cadillac dealer hit me for 85.00 on my last one.

BeagleBrains
09-14-05, 09:14 PM
So you admit that you are completely brainwashed by Jiffy Lube. :cookoo:
More a pride thing. I will not casually let anything be less than as good as I can make it. Note: I have never set foot in a 'Jiffy' anything. You get what (as little as) you pay for. They could not supply me with the $200.00 Canton filters that I use on my V and my Jeep.

Barak
09-15-05, 01:02 AM
They could not supply me with the $200.00 Canton filters that I use on my V and my Jeep.

You spend $250 for an oil change every 3000 miles?!:bonkers::eek:


More a pride thing.

You might want to see a psychiatrist about that.



Amazing how most of the population is happy to eat and drink chemicals, live on an improper diet, get too little sleep, slug a few too many beers...
But heaven forbid us letting our precious cars have a few too many particles in the oil.

Perhaps the best post yet on this thread.



With lean burn engines and unleaded fuel to say nothing of synthetic oils, the rules have changed. Look at how long the plugs last now.

It would seem that lean A/F ratios would cause additional cylinder wear due to the lack of lubricity provided by the fuel. I do realize though that fuel dilution of the oil is less of an issue with leaner combustion.

Lean conditions would wear spark plugs faster due to the increased required voltage needed to light the mixture. I would attribute the long life of modern spark plugs primarily to their platinum/irridium tips and the more precise fuel control capabilities of modern fuel systems.

a64pilot
09-15-05, 08:16 AM
Lean conditions would wear spark plugs faster due to the increased required voltage needed to light the mixture. I would attribute the long life of modern spark plugs primarily to their platinum/irridium tips and the more precise fuel control capabilities of modern fuel systems.
The current is there with these ignition systems, trust me. The leaner burn as a result of more precise fuel control as well as the absence of lead and of course more modern materials all add up to a 100,000 mile plug.
Fuel is a poor lubricant. Richer than necessary mixtures will actually wash the oil from cyl walls and cause excessive cyl/ring/piston wear.
Our engines operate almost entirely on the lean side of best power as far as mixture is concerned. Aircraft as an example typically operate 100 deg or so rich of peak because they lack the modern fuel systems our cars have. It's hard on the oil, engine and plugs as well as being inefficient. There is a recent trend to operate 50 to 100 deg lean of peak, but this requires a set of specially calibrated fuel injectors to do so.

Barak
09-15-05, 01:15 PM
Our engines operate almost entirely on the lean side of best power as far as mixture is concerned.

Our engines operate at stoich at part throttle in order to meet ULEVI emissions. At WOT, our engines are definitely on the rich side of best power. If the engine ran lean, then it wouldn't be able to meet the NOx requirement for ULEVI emissions.



Fuel is a poor lubricant. Richer than necessary mixtures will actually wash the oil from cyl walls and cause excessive cyl/ring/piston wear.

I've heard this argument before, but when gasoline's lubricating properties are compared to high ethanol fuels, upper cylinder wall wear increases due to ethanol's poor lubricity. It would seem that if you relied on oil to lubricate the upper cylinder walls, the engine would burn excessive oil. The fuel washing oil away from the walls oil only makes sense if the oil rings are allowing oil to pass above the piston or if the fuel isn't being properly atomized. I think the argument is a moot point anyway since modern ring coatings don't require fuel or oil to provide a slick surface.

hd750
09-17-05, 12:13 AM
When you change you oil is it down a quart @3K miles like mine?

benjet
09-17-05, 12:48 AM
When you change you oil is it down a quart @3K miles like mine?

Sound about right. LS6 can burn up to 1qt per 1k and still be considered acceptable.

a64pilot
09-17-05, 10:50 AM
Our engines operate at stoich at part throttle in order to meet ULEVI emissions. At WOT, our engines are definitely on the rich side of best power. If the engine ran lean, then it wouldn't be able to meet the NOx requirement for ULEVI emissions.
What percent of the time are you close to WOT? Most of us in reality spend very little time there. That why I said our engines operate most of the time lean and not all of the time.
Best power if I remember correctly is rich of stoich if I understand what you
mean by stoich isn't it?
The whole point of my comment was not to get real specific, but to point out that modern engines operate at a greater efficiency than engines of say 40 years ago and because of this and many other things like tighter manufacturing tolerences they contaminate the oil at a much slower rate. Oils are much better as well. It's because of these and other things that the oil change interval of 3,000 miles is no longer valid. That was the only point I was trying to make. That if you are close to stock that a 3,000 mile change interval for most of us is a waste of time,money and rescorces.

rand49er
09-17-05, 11:08 AM
"Stoichiometric", as I recall, is the ratio of air to fuel (by weight) which when burned will (theoretically) yield only carbon dioxide and water (i.e. no unburned hydrocarbons or carbon monoxide). It used to be that in order to meet exhaust emission standards, auto makers went to three-way catalytic converters and oxygen sensors were employed to help maintain stoichiometry in the A/F ratio. Frankly, I've been away from it so long, now :( , I'm not sure it's all that simple any more. :hmm: Anybody?

Barak
09-17-05, 06:04 PM
The whole point of my comment was not to get real specific, but to point out that modern engines operate at a greater efficiency than engines of say 40 years ago and because of this and many other things like tighter manufacturing tolerences they contaminate the oil at a much slower rate. Oils are much better as well. It's because of these and other things that the oil change interval of 3,000 miles is no longer valid. That was the only point I was trying to make. That if you are close to stock that a 3,000 mile change interval for most of us is a waste of time,money and rescorces.

Amen to that.


What percent of the time are you close to WOT? Most of us in reality spend very little time there. That why I said our engines operate most of the time lean and not all of the time.
Best power if I remember correctly is rich of stoich if I understand what you
mean by stoich isn't it?

By stoich I meant 14.7:1, the ideal mixture for emissions. Best power is more like 12.5-13.0:1, but like all stock engines at WOT, our stock calibration is on the rich side and probably below 12.0:1. At part throttle the mixture should always be hovering around stoich.


It used to be that in order to meet exhaust emission standards, auto makers went to three-way catalytic converters and oxygen sensors were employed to help maintain stoichiometry in the A/F ratio. Frankly, I've been away from it so long, now :( , I'm not sure it's all that simple any more. :hmm: Anybody?

If you look at the evolution of the LS1/LS6 in terms of emission compliance, the engine has been making more power while meeting stricter emissions and all with fewer add-on emission components. Case in point, the EGR and secondary air systems found on early LS1's are nonexistent on later model LS1's, LS2's and LS6's. The '01 LS6 used 4 catalysts to meet the same emission standards as the '02 LS6 which only had 2 catalysts. So it could be argued that emission compliance is getting even simpler than before, at least in terms of number of components.