: Change oil @ 3k or when comp says to?



andrewdeville03
02-09-07, 07:21 AM
Should I change my oil at 3,000 miles or when the dash computer says to? I'm at 3,050 miles since last change, but dash read-out says engine oil is at 75%.

EcSTSatic
02-09-07, 07:50 AM
3K is old school when oil and engine technology wasn't as refined, no pun intended. It's just my opinion but I recommend using the OLM or the new thumbrule of 5K.

Cartalk (http://www.cartalk.com/content/columnsbu/Archive/1997/November/12.html)

BodybyFisher
02-09-07, 09:00 AM
In the old days the owners manual stated that if you took short trips to change the oil every 3000 miles and if you took long trips 7500 miles (if in dusty or fleet conditions change it more often). That was a hard thing for an owner to monitor accurately. The GM Oil life monitor, monitors the length of your trip, oil temp, engine RPM, coolant temp, etc using an algorithm and it makes a better determination of when to change the oil. Plus oils today are so much better than they were AND fuel injection does not contaminate the crankcase with flooding/fuel like carburators and chokes did. So to change your oil at 3000 miles is wasteful and un-necessary. Read about your OLM here:

http://www.cadillacforums.com/cadillac-tech.html#oillife

I can NOT claim credit for the following, it was written by a very knowledgable person, I had saved it in a WORD doc on my hard drive, this SHOULD clear up any apprehensions you have about the OLM:

The GM engine oil life monitor counts engine revolutions and accumulates the number for the basis of the oil life calculation. It then adds deterioration factors for operating temperature, start up temperature, soak times, ambient, coolant temperature, etc... There are a LOT of factors that "adjust" or affect the slope of the deterioration but the fundamental deterioration is traced back to the ZDP depletion that is inescapable with engine revolutions. The specific rate of ZDP depletion is readily measurable for any given engine so that is the fundamental item that is first calibrated for the oil life algorithm to tailor it specifically to that engine.

You would obviously like to get the oil out of the engine before the ZDP concentration gets so low that it is ineffective at being at the right place at the right time and preventing engine wear so that becomes the long term limit on oil life for that application.

The other things that determine oil life such a acid build up, oxidation, petane insuluables such as silicon from dust/dirt, carbon or soot build up from the EGR in blowby, water contamination, fuel contamination, etc.... are all modeled by the multipliers or deterioration factors that "adjust" the immediate slope of the line defined by the engine revolution counter as those items can be modeled in other ways and accounted for in the immediate slope of the ZDP depletion line.

The algorithm was developed over the course of many years by several lubrication experts at GM Fuels and Lubes, spearheaded by Doctor Shirley Schwartz who holds the patents (with GM) for the algorithm and the oil life montitor. I had the luck of working directly with Dr. Schwartz when the idea of the oil life monitor first progressed from the theoretical/lab stage to real world testing/development/validation. There were fleets of cars operated under all conditions that deteriorate the oil life for any and every reason and , thru oil sampling and detailed analysis of the oil condition, the algorithm was developed, fine tuned and validated to be the most accurate way invented yet to recommend an oil change interval by. As just one example, I have seen cars driven side-by-side on trips, one towing a trailer and one not, for instance, to prove the effectiveness of the oil life monitor in deteriorating the oil at a faster rate just because of the higher load, higher average RPM, higher temps, etc...and it works flawlessly.

The oil life monitor is so effective because: it is customized for that specific vehicle/engine, it takes everything into account that deteriorates the oil, it is ALWAYS working so as to take into account THAT INDIVIDUALS driving schedule, and it tailors the oil change to that schedule and predicts, on an ongoing basis, the oil life remaining so that that specific individual can plan an oil change accordingly. No other system can do this that effectively.

One thing is that I know personally from years of testing and thousands of oil analysis that the oil life algorithm works. There is simply no argument to the contrary. If you don't believe me, fine, but, trust me, it works. It is accurate because it has been calibrated for each specific engine it is installed on and there is considerable testing and validation of the oil life monitor on that specific application. NOt something that oil companies do. They generalize....the oil life monitor is very specific for that application.

Oil condition sensors in some BMW and Mercedes products are useful, also. They have their limitations, though, as they can be blind to some contaminates and can, themselves, be contaminated by certain markers or constituents of certain engine oils. Oil condition sensors can only react to the specific oil at that moment and they add complexity, cost and another potential item to fail. One other beauty of the GM oil life monitor is that it is all software and does not add any mechanical complexity, mass, wiring or potential failure mechanism.

There is considerable safety factor in the GM oil life monitor. Typically, I would say, there is a 2:1 safety factor in the slope of the ZDP depletion curve....in other words, zero percent oil life per the ZDP depletion is not zero ZDP but twice the concentration of ZDP considered critical for THAT engine to operate under all conditions reliably with no wear. This is always a subject of discussion as to just how low do you want the ZDP to get before the oil is "worn out" if this is the deciding factor for oil life. We would tend to be on the conservative side. If the oil life is counting down on a slope that would recommend a 10K change interval then there is probably 20K oil life before the ZDP is catostrophically depleted....not that you would want to go there...but reason why many people are successful in running those change intervals.

dkozloski
02-09-07, 09:53 AM
The OLM was designed and developed by Dr. Shirley E. Schwartz who is acclaimed worldwide by her peers as one of the foremost lubrication engineers in the world. Do a Google search on her name and it's an easy decision to make about relying on her machine.

JohnnyO
02-09-07, 10:36 AM
It's fine to wait until the computer tells you to. Also remember that a Northstar holds 50% more oil than most other cars (7.5 qt vs. 5.0 qt) so it's good for longer simply on that basis alone.
I sent used Mobil 1 from my dad's '04 to a lab after 11,200 miles, the OLM was down to about 4%, and they said it was fine and could have gone longer.
If you want to go by miles instead, in most cases 10,000 miles should be fine, even on conventional oil. 7500 if you want to be picky. It will be fine. Really.
Just use a quality oil and filter (AC, NAPA Gold).

www.blackstone-labs.com

codewize
02-09-07, 08:55 PM
I just spent all this time typing this in that other oil thread. Changing oil every 3k is wasting money and damaging your engine.

It's been proven time and time again that virgin oil (oil just out of the bottle) is worse for your engine than oil with 5000 miles on it. Oil in fact does have a break in period. If you change the oil every 3k you're throwing away oil just as it's becoming good.

Ranger
02-09-07, 10:08 PM
OK, your gonna have to explain that one. First time I have ever heard that. What is it based on? Never heard of oil getting better with time and miles.

dkozloski
02-09-07, 10:35 PM
OK, your gonna have to explain that one. First time I have ever heard that. What is it based on? Never heard of oil getting better with time and miles.
I was going to leap to that bait too. It sounds to me like a leadin to a sales pitch for reclaimed crankcase drainings.

clarkz71
02-10-07, 05:11 AM
I'd like to know the source on that myself.

codewize
02-10-07, 10:20 AM
Ohh now I'm in a bad spot :) It was in one of the articles someone posted about testing oils. They tested the oil at 500 mile increments for the first 4 or 5k and proved that once the oil was 'broken in' it had better protection properties than oil fresh out of the bottle.

I'll have to look around and see if I can find it but I swear to you guys that I did read this from what we expect to be a reliable source. We've had a few small discussions about it recently also and there were 4 or 5 members who agreed so I guess they either read the same thing or heard it somewhere else.

No lead ins or marketing here. Just something I read. I'll try to find it for you.


EDIT: I just did some Googling and couldn't find it. It's on one of those oil analysis pages that someone posted a while back where they did an extensive comparison of oils.

99Classillac
02-10-07, 01:56 PM
So I pose this question. These GM Oil Life Monitors take into account all these different factors to determine when the ZDP levels are so low that it will damage your engine. In our older cars, like per say, my 1999 Deville, oil being sold then had more ZDP levels in it. Nowadays, the oil companies are reducing the ZDP. So, my OLM is outdated then right? It cannot reliably determine the depletion of ZDP because the oil I put in it now has less ZDP to start with than the oil from 7 years ago when they made my car. Right? If so, is there a way to update my OLM software, not that I would do it, but is there?

thu
02-10-07, 02:59 PM
In my 1993 Deville, I changed the oil when the computer told me to. That was around 7500 miles each time. Engine is still going strong, not a thing wrong with it - 298,000 miles!

BodybyFisher
02-10-07, 03:04 PM
So I pose this question. These GM Oil Life Monitors take into account all these different factors to determine when the ZDP levels are so low that it will damage your engine. In our older cars, like per say, my 1999 Deville, oil being sold then had more ZDP levels in it. Nowadays, the oil companies are reducing the ZDP. So, my OLM is outdated then right? It cannot reliably determine the depletion of ZDP because the oil I put in it now has less ZDP to start with than the oil from 7 years ago when they made my car. Right? If so, is there a way to update my OLM software, not that I would do it, but is there?

Good Thought I raised that thought over here, we are having that discussion right now!

http://www.cadillacforums.com/forums/northstar-performance-technical-discussion/97698-motor-oil-killing-our-cars-long.html

WildLife
02-10-07, 03:22 PM
A time or two I have waited untill the Change Oil Now
message..............
Reset 1 time and went additional 25 %.
Mostly change around 15% left value.
Synthetic, Always new filter.
Milage varies.

dkozloski
02-10-07, 03:38 PM
The Northstar OLM was validated with generic dinosaur oil. The remaining ZDDP was one factor monitored but not the only consideration. There is a generous safety margin. I'd be looking around for something else to worry about. Worrying about this is like stomping on pissants while elephants are running up and down the halls.

Ranger
02-10-07, 03:56 PM
I don't know Code, sounds fishy to me. Not doubting that you read it somewhere, just that I have never heard of it before. I have to wonder what the definition of "breaking in oil" is. Something else I have never heard of before. It would be interesting reading if you can find it. Probably good for another 15 page oil thread.;)

dkozloski
02-10-07, 04:43 PM
I have heard that under stress, long chain hyrocarbon molecules can be physically torn apart causing the oil to thinout and that they will heal themselves causing the oil to return to normal. This breakin stuff has the smell of an urban legend.

TripleblackETC
02-10-07, 05:16 PM
I listen to what the computer tells me. When it says "change oil," I figure it's time to change the oil.

I just hope it never tells me to go jump off a bridge. I'd probably obey. >=)

codewize
02-10-07, 10:00 PM
I'll continue my hunt but I think we all agree that 3000 miles is too often and we can got AT LEAST as long as the computer lets us. There are so many oil threads here it may take a while to locate that one.

They certainly didn't say leave it in there forever and it'll get better with age but I think it was something like it had better lubrication properties between 3 and 5k than it did new out of the bottle. These numbers are examples only, don't quote me on them.

I~LUV~Caddys8792
02-10-07, 10:59 PM
I go off the OLM. I don't see any reason GM would use it if it was a bad device.

My brother is a good example of the "always three month" plan. He drives about 25 miles a week, just to school and back, or to work and back..both trips are less than five minutes, so his engine never gets to operating temp, and his oil turns to shit. I had it changed on Monday, and it had accumulated 1200 miles since the last change, which was at the end of August! We went 5 months/1200 miles on the same oil! We tell him he has to take the car out for longer drives, but he doesn't listen, oh well, it's his car and it's only a '96 Sentra..

Jesda
02-11-07, 04:28 AM
OLM cares more about your convenience and the environment than your engine.

Follow the OLM to 25-30% and change it.

JimHare
02-11-07, 07:36 AM
I just changed the oil and filter in the Eldo yesterday, at just about exactly 75K (Ok, it's 74,994...) The OLM was at 2%... I don't remember exactly what the mileage was last time, but it was about 65 or 66K back in the early spring. I put in Walmart 5w/30. I drained in to a pan, and refilled old 1-qt empties. I filled 7 of them, so considering the amount soaked into the old filter (AC Delco PF61), I probably didn't burn much, eh?

Now that I'm driving a regular route M-F, it will be easy to see what kind of wear I get out of this change.

GreenMachine
02-11-07, 08:34 AM
Code it wasn't 5,000 mile oil better than virgin oil, it was 3,000. They did a bunch of used oil analysis on BITOG about it and found that engines with the oil change at the 2000-3000 oil showed more wear overtime than engines which changed at the 5,000 mark. I too cannot find the link to that thread, so maybe the took it down because further reasearch proved it wrong? It sounded funny to me. The main reason they said this was a problem was because as the old coatings off additives were "washed off" by the new oil it took some time to recoat with active additives. Basically they found most of the wear in an Oil change interval occurs in the first 1000-2000 miles.


Also I asked about Northstar flat tappets over there, we have nothing to worry about:
http://theoildrop.server101.com/forums/favlinker.php?Cat=0&Entry=1847&F_Board=UBB1&Thread=784446&partnumber=&postmarker=

I should note the ticking I mentioned in that thread has disappeared since I did some WOT runs, or has become virtually unnoticeable if their at all. Oil consumption has appeared to have also dropped, not sure if that is related to or not to adding High Mileage Kendall (to the existing synthetic blend regular stuff) in the form of 2 qts to bring the dipstick to full.

codewize
02-11-07, 12:42 PM
That all sounds about right. What I was saying is that your oil with 3000 miles on it is better left in the engine than being drained. As I said it doesn't get better with time, but during a certain time, just about when most people drain the oil, it's just becoming the most useful.


Code it wasn't 5,000 mile oil better than virgin oil, it was 3,000.

Murphyg
02-15-07, 09:23 PM
Do it when the comp says and both you and your Caddy will be happy.

GreenMachine
02-18-07, 06:44 AM
Had the oil changed yesterday @ 3441 miles with the oil life monitor telling me I had 11% left.

Cold weather, short trips, having to rock the car, I'm sure shortened this interval up.

It works.

dkozloski
02-18-07, 01:49 PM
Had the oil changed yesterday @ 3441 miles with the oil life monitor telling me I had 11% left.

Cold weather, short trips, having to rock the car, I'm sure shortened this interval up.

It works.
The OLM automatically keeps track of those factors for you. Not to worry!:)

thu
02-18-07, 05:57 PM
Yes! It looks like your OLM is working just fine. I had my oil changed a week ago when the OLM hit 0% - 12,457 miles.