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Interesting info regarding oil drain interval

37K views 439 replies 46 participants last post by  shortyb 
#1 · (Edited)
http://www.sae.org/technical/papers/2007-01-4133
Abstract:

Engine oils are subjected to a series of industry standard engine dynamometer tests to measure their wear protection capability, sludge and varnish formation tendencies, and fuel efficiency among several other performance attributes before they are approved for use in customer engines. However, these performance attributes are measured at the end of tests and therefore, do not provide any information on how the properties have changed during the tests. In one of our previous studies it was observed that engine oil samples collected from fleet vehicles after 12,000 mile drain interval showed 10-15% lower friction and more importantly, an order of magnitude lower wear rate than those of fresh oils. It was also observed that the composition of the tribochemical films formed was quite different on the surface tested with the drain oils from those formed with fresh oils. The objective of this investigation is to demonstrate how the friction and wear performance changed with oil drain intervals. A fleet of three vehicles was run in Las Vegas and oil samples were collected at various drain intervals from 3,000 miles to 15,000 miles. As in the previous study, the results showed that the aged engine oils provide lower friction and much improved wear protection capability. These improvements were observed as early as the 3,000 mile drain interval and continued to the 15,000 mile drain interval. The composition of tribochemical films formed on the surface with the 3,000 mile drain interval is similar to that formed with the 12,000 mile drain interval as seen before. These findings could be an enabler for achieving longer drain interval although several other factors must to be considered.
Moral of the story: Those of you who change oil every 3-5k to be on the "safe side" are being counterproductive.

Don't change it too often and increase wear.

Don't change it too seldom and increase wear.

There's a sweet-spot, if you will.



BTW - Thanks to jpr for initially sharing this article.
 
#2 ·
How interesting! :wow: One could extract a lot of useful from that article :4ngie:

Thanks for sharing :thumbsup:
 
#3 ·
So... the best thing to do is to talk your buddies into letting you "help change their oil" at 3-5,000 miles, and then offer to "dispose of it" for them for free. You just don't have to tell 'em you're going to "dispose of it" by pouring it into your engine!
 
#10 ·
I remember reading about an service technician that brought used oil home from his work and used it in his own cars, because he found it just a waste when people insisted the oil be changed every 3-5000 miles when he knew the oil would be good for 10-15,0000 miles. :rofl:

Pure BS, for what it cost to analyze my oil, I just change it and you can see the smile on the engine :) 5K me majic # plus I enjoy doing this
LOL, you think you are smarter than the SAE? Wow. Well, before I say anything else mean, do you use Mobil 1 0w-40 and if you do, could you ship it to me if I pay for shipping?
 
#8 ·
you dont have to get an analysis. I've done one so far, and i've got a few more to do. So far it's pointing to about 9-10k. (on mobil 1 0w-40)

On my next change i'm going to let the SI count down to 5k miles and see how it's doing at that point. Using the SI is the best way to determine oil life to begin with, but i wasnt thinking about this last time i changed and forgot to reset it :banghead:. So mileage is all i have to go by this time...
 
#13 ·
I like to do it every 7500 which for me is twice a year. i do it once i put the skis away and then i do another in the fall when i take the skis out.
 
#20 ·
maybe we could, if you explain us what do the two have to do with each other?
 
#21 ·
I don't know. By no means am I doubting the results of the study, nor do I ever doubt JPR, but I beat the living snot out of my motor. Almost 125k miles on it, and it pulls like the day I bought it. I've replaced the gasket seal twice and did the VANOS seals recently too. Everything looks and is near perfect...no sludge/carbon buildup, and all 6 cylinders pumped out near perfect #s in a compression test. My oil's been changed between 3-6k miles, and I have no doubt I'll get well over 200k miles out of it. While I understand and respect the test, I don't think I can be persuaded to change my ways. Not because I think I'm right and they're wrong, but just because what I've been doing works fine for me.
 
#23 ·
I don't know. By no means am I doubting the results of the study, nor do I ever doubt JPR, but I beat the living snot out of my motor. Almost 125k miles on it, and it pulls like the day I bought it. I've replaced the gasket seal twice and did the VANOS seals recently too. Everything looks and is near perfect...no sludge/carbon buildup, and all 6 cylinders pumped out near perfect #s in a compression test. My oil's been changed between 3-6k miles, and I have no doubt I'll get well over 200k miles out of it. While I understand and respect the test, I don't think I can be persuaded to change my ways. Not because I think I'm right and they're wrong, but just because what I've been doing works fine for me.
This is why the service indicator counts mileage based on fuel consumption, not actual mileage. Harder driving = less mpg = more frequent oil changes.

BMW may not be a perfect car company, but they're way ahead of you on this.
 
#59 ·
Lifetime tranny fluid is no longer BMW's claim, so I don't know what you're talking about :dunno:
Mercedes I know for sure has retracted their claim as well about lifetime transmission fluid and at first went to 100k miles and now says to do it ever 39k miles. The problem though is that these facts are only published in TSBs and aren't made readily available to the public or even to every service adviser. Could you imagine how pissed you'd be if you actually took their advice that the fluid could last forever and then your transmission died but you found out that your OEM was now saying to change it every 39k miles :rofl: there would be more than a few lawsuits :ben:
 
#55 ·
The abstract mentioned by the OP says:

"These improvements were observed as early as the 3,000 mile drain interval and continued to the 15,000 mile drain interval."

Their comment would appear to support BMW's target for oil change interval.

It's a pity they didn't run the "fleet" of three cars to longer mileage intervals. We might have learned that the improvements observed continued after 15,001 miles.

I wonder at what mileage interval the improvements are no longer observed.

I wonder what happens to those observed improvements when the vehicle approaches Castrol's 30,000 mile figure.
 
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