UnderdogI've never done an oil analysis, just read lots of them from you fine folks who do them and post the results.
But, I switched to synthetic oil in the late 90's and soon thereafter started doing annual oil changes. I typically drive 6-8k miles in a year, sometimes more. My wife usually drives less than that. And my beater truck less still. (I put dino oil in it) But, I just do my oil changes in July and call it good. No problems. Had my Saturn for 7 years, my wife's Saturn for 10 years, my first Miata for 6 years, my wife's MINI for 6 years, and her first Miata for 7 years. Annual oil changes on all of them. (or more often if warranty required it)
And here's the kicker for me. Brand new 2006 MINI Cooper. BMW put their fancy oil monitoring computer system on it to tell you when to change the oil based on how the car is driven, not just mileage. (I think it actually counts engine revs, or the amount of fuel burned, or maybe some combination of the two) The first oil change came due on that car at almost 10k miles. And the second one was over 11k miles. They do require synthetic oil in these cars. But, that's when I decided... you know, if a 10k+ synthetic oil change interval is good enough for BMW engineers, it's good enough for me!
That's when I lost any and all guilt I may have had about doing annual oil changes. I'm not driving much more than 10k miles in a year. And if I did, it would be easy highway miles. So, I just don't even worry about it.
5000 or 7500 mile oil changes on the Mirage? Nah. Once you're out of warranty, use good synthetic oil and change it every year or 10k miles and be happy.
(No sciences were harmed in the making of this post. Pure speculation and hear-say.)
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