time based oil changes?

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Originally Posted By: doublebase
You'd think that the amount of time/distance people go between oil changes around here, oil prices would have dropped do to supply and demand factors. No one seems to be doing the three month 3,000 mile interval anymore. Most go at least twice that and many are going much further...yet no price change despite oil consumption/use being cut in half???


Whatever we do gets stomped out by the growing appetites in Asia where 3.5 billion people, with a rising middle class, keep demanding more oil.
 
Originally Posted By: virginoil

AN ENGINE OIL LIFE ALGORITHM see link below especially Chapter 4 on Page 74 of the document

https://etda.libraries.psu.edu/paper/9507/5943


Great find, fun reading! I would caution any reader about Master's Thesis write-ups. They are done by very inexperienced people. They aren't always corrected by professors, who themselves may not have enough experience sometimes either. A lot of good info, but watch out.
 
A quote from the Pennsylvania State paper cited above:

"GM studied the results and suggested that, when using even a borderline SG quality mineral oil, a vehicle can be driven under freeway conditions for 10,000 miles between oil changes with only minimal oil degradation and without serious damage to the engine. In case of synthetic oil, the vehicle can be driven above 12,000 miles. During short-trip service, the engine oils used in the study degraded rapidly due to contamination and an oil-change interval of 3000 miles is recommended."

Basically, if you're long-tripping, go more miles between oil changes. If short-tripping, go less miles. It all results in 6 months for a conventional oil, and 12 months for a synthetic. You could be careful and only ever go 6 months for BOTH conventional and synthetic when short-tripping. Yet, it all comes down to time, not miles.
 
I've done UOAs on 2 and 3 year changes on my Camaro that gets about 500 miles/year with no short trips and all have come back fine.
 
Originally Posted By: Quattro Pete
Originally Posted By: turtlevette
I don't understand the 1 year overall limit by the oil manufs. How can oil degrade just sitting around? TBN doesn't affect ability to lubricate so I'm not that concerned about that.

Oil gets exposed to outside conditions and oxidizes. It also gets exposed to moisture and fuel that naturally happen during start/stop cycles and warmups and cooldowns. Over time, this causes the oil to become acidic and it starts to eat away at your engine.

Not saying 1 year is the magic number when this becomes an issue. But time is a factor.


I wonder if it's to cover the people who start and drive 1 mile. Every start a cold start, never warmed up, etc.
 
Originally Posted By: supton
I wonder if it's to cover the people who start and drive 1 mile. Every start a cold start, never warmed up, etc.

If it's cold out, even a 5 mile trip will not allow the engine to fully warm up. Wife has a 4 mile commute. With temps in the teens and 20s, at the end of it her coolant hasn't even reached normal, much less her engine oil.
 
No single rule makes sense. It is all about how the oil is used. If it just sits, years. If there are a lot of short, cool trips, just a few months. If there are long warm drives, thousands of miles.
 
Another surprisingly effective oil change interval indicator is to just count days when the car is started. ... That way, if you put on a lot of miles, you still count that as a 1 day you used the car. ... If you drive only 1 mile each way, no warm up, you still count that as 1 day you used the vehicle. When you get to a day-count of, say, 90, you change the oil. Its that simple.
 
I have extended my motorcycle OCI to 18 months and will do a UOA the with TBN/TAN just to give me a benchmark. I do think with the 10w50 syn oil I can go 24 months or 5000 miles.

The factory OCI is 12 months 6000 miles.

I know guys who go several (3-4) years between changes because they ride about 1000 miles annually
 
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Without reading everything else, I feel if you get your engine to temperature enough on the highway, going the recommended distance per fill seems reasonable.

If you're a grandma driving 2 miles a day and hardly moving the temperature gauge, 3 months changes should be done.
 
I have posted this before "stupid OEMs know how to build a new vehicle provide a 3 year minimum warranty but appear to be clueless and can not be trusted with the OEM users manual that it comes with."

Perhaps if we had to be pay for the OEM manual separately as an overcharge it may be held at a different level of esteem and there may be chance the extreme conditions of use will be read and applied by the vehicle owners.
 
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