Extended time (but not mileage) interval between oil changes?

[kreativ]

My uncle's Lexus calls for oil changes every:
7500 miles or 6 months (normal service schedule)
5000 miles or 4 months (severe service schedule)

His use of the car doesn't meet any of the conditions set by Lexus for the severe service schedule (he uses it for a 50 mile round-trip, mainly highway, twice a week. Ambient temperatures between 40-90 year-round). The good thing is that he has his oil changed by the dealer every 5000 miles anyways. The bad thing is that it takes him almost a year to reach 5000 miles in that car.

I advised that he should change his oil every 6 months at least, but he thinks the time interval is provided simply for those who don't like keeping track of miles.

Is there solid evidence that oil loses its lubricating abilities simply based on time in an engine?

And with his driving pattern, is he asking for trouble with an "extended time interval" oil change using dealer-supplied dino oil?

 

[SEBZX79]

He is fine...

 

[cryptokid]

i dont see any problem. my dad had ran 10 year drain intervals on oil.

he has a 60 chevy up in storage up north, it gets about 50 miles a year use. he hasnt changed the oil in around 10 years. i think the oils got like 500 miles on it or somthing. it still looks clean!

edit: i forgot to mention, hes been doing this for the last 30 years with this car.

 

[John_E]

I have changed the oil every 6 months on cars driven less than 5K miles / 8K km per year, but with city ahd short-trip driving, I am concerned about condensation. Your uncle's situation is much less "severe" than mine.

 

[pitzel]

If the car is in warranty, stick with the manufacturer's time-based interval recommendation. A bit of wasted oil isn't worth even the remote chance of a denied warranty claim, and that 'wasted' oil can always be put into another engine you own or properly recycled.

If the car is not under warranty, changing on a 1-year interval is perfectly safe, and likely, with a good synthetic or extended drain-specific oil (M1 EP, XD-3, Delvac-1, Rotella Synth, etc.), you could drain on 2 or 3 year intervals.

Oil does not 'degrade' by merely sitting in the crankcase, and condensation should be pretty much a non-issue.

 

[Dr. T]

No, mileage is more important than time....and 6 months is nothing...ie. probably just a rough estimate on Toyota's part re: when an average motorist would achieve 7.5k mi.

And...as always....use syths...

 

[kreativ]

Thanks for clearing up the time interval matter for me. Sounds like 1 year oil change intervals will be just fine for my Uncle. His car just gets whatever bulk dino oil the dealer uses though.

quote:

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Originally posted by John_E:
I have changed the oil every 6 months on cars driven less than 5K miles / 8K km per year, but with city ahd short-trip driving, I am concerned about condensation. Your uncle's situation is much less "severe" than mine.

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With this type of driving, how would you deal with condensation? Would taking the occassional highway trip take care of it? Or is condensation something that irreversibly affects the properties of the oil?

[ February 18, 2005, 07:24 AM: Message edited by: kreativ ]

 

[Spector]

I have one with about 2500-3000 miles a year, been doing the 1 year change for several years now, UOA is fine. Does help to drive at least 10 miles or so when the engien is started though

 

[jthorner]

I think that the months recommendation is based on the assumption that people with low mileage accumulation might be using the car frequently, but for very short trips. The proverbial little old lady who works 1.5 miles from home and stops at the grocery store on the way home from work. Then she makes a 10 mile round trip on Saturday to visit her sister and a 5 mile round trip on Sunday to church. Doing this routine she would only put 1170 miles on a car in six months, but would have fuel dilution, water condensation and blow-by issues. For this hypothetical driver, changing the oil once every six months (or even once every three months!) would be a good idea.

Where the car is parked overnight matters as well. You know all of the dew that collects on a vehicle outside over night? Well condensation can happen inside the crankcase as well. Parking the car in a garage, even unheated, provides a great deal of added protection.

A vehicle which spends most of it's time stored in a protected garage and then enjoys occassional longer trips once or twice per week does not have nearly the fuel dilution and water condensation issues as does the low mileage, but frequently driven vehicle.

In short, your uncle is fine, but not all low usage situations justify 1 year OCIs ... and I don't care how good the oil is, it cannot magically rid itself of contamination.

John