When It Comes to Oil Changes, Miles Count More Than Months

Dear Car Talk:

I have a 2001 Ford F-150 with 143,000 miles on it that is in excellent shape. When I purchased it, I also bought the "lifetime oil change plan" for $300.

Now that I'm retired, I only drive it around 3,000 miles a year. The oil change plan provides for quarterly oil changes.

Since I am only driving 3,000 miles in a year, is it OK to only change the oil once or twice a year, or does the oil degrade over time just from sitting there and not only from miles driven? -- John

You're the reason they jacked up the price of that lifetime oil change plan to $2,500, John. By now, they might be putting Filippo Berio Extra Virgin Olive Oil in your crankcase, hoping to kill off your F-150 and finally get rid of you.

Oil degrades from being used, John. Not from sitting around. As the oil circulates with the engine running, it gathers up contaminants and holds them in suspension. Eventually, it gets dirty, and can't absorb any more carbon, soot or water, and then it can't lubricate as well. That's when it needs to be changed.

Modern engine oils, even the cheap stuff they probably give you with your free oil changes, can easily go 5,000 miles before needing to be changed. Probably longer. Synthetic oils, which are even better, can go twice that long.

If you really neglected your oil for tens of thousands of miles, the long chain molecules that do the lubricating would eventually break down. But dirt is going to be an issue well before chemical breakdown is.

So the answer is, yes, you can get less frequent oil changes, John. You might try negotiating with the dealer. Say "Hey, look, you're sick of seeing me every three months for my free oil and filter. How about you give me full synthetic oil, and I'll just come in once a year." They'll pay more for the full synthetic, but they'll save three filters, an hour and a half a year of labor and the annoyance of having to be reminded that they're making three bucks each time they change your oil.

You'll be fully protected and give them fewer opportunities to sabotage your engine. Even if they won't splurge for the full synthetic oil, with only 3,000 annual miles, you can still cut back your oil changes to once or twice a year with no worries, John.


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