Should we change the oil at 7,500 miles or 3,750 miles?

Dear Car Talk

Dear Car Talk | Nov 01, 1997

Dear Tom and Ray:

My wife Deborah and I have a constant and ongoing discussion about oil
changes and when to do them. We recently bought a 1997 Honda Civic. The
dealer told us it was important to change the oil every 3,000 miles. The
owner's manual gives two sets of conditions for oil changes. It says for
"normal" driving to change the oil every 7,500 miles or 12 months. For
"severe" driving, change it every 3,750 miles or six months. Based on the
descriptions, I'm somewhere in between. I say we should therefore change
the oil every 3,750 miles and follow the directions for severe driving. My
wife is an avid fan of your radio show and says we should change every
7,500 miles. We need arbitration. -- Richard

TOM: Wow. I think this may be the first time we're going to answer a
question like this and not initiate divorce proceedings. It just so happens
that our recommendation for oil changes is right in between -- 5,000 miles!

RAY: Driving gently and changing the oil regularly are probably the two
best things you can do for your car. But it's important to remember that
oil-change intervals are just estimates.

TOM: Right. You put this stuff called oil in the engine. It lubricates all
of the moving parts and collects a bunch of contaminants as it swirls
around. And as it gets older, it doesn't lubricate quite as well and can't
hold onto any more contaminants. And that's when you want to dump it out
and put in some new stuff.

RAY: Is there a magic number of miles at which the oil is suddenly no good?
No. The rate at which an oil breaks down is different for every car on the
road, depending on the car, the driver/driving, and the environment. So you
take your best guess.

TOM: We used to recommend 3,000-mile oil changes because that practically
guaranteed that the oil wouldn't be in the engine long enough to break
down. But with the improvements in oils, engines (and the problems of used
oil disposal), we changed our recommendation to every 5,000 miles.

RAY: And even 5,000 may be too often, but we think it's a good estimate.
The dealer would obviously like you to change it more often because for
every oil change, he gets ... what? Paid!

RAY: And the manufacturers would like you to think that you can wait longer
between changes because they're mostly concerned about getting you through
the warranty period. Plus, the promise of less maintenance appeals to
potential buyers of these cars.

TOM: And neither one of these parties is wrong. One is just being
extra-cautious, and the other is being perfectly reasonable. Since we lean
a little toward the cautious side in this regard, we recommend an oil
change every 5,000 miles.

RAY: But remember, even 5,000 miles is just an estimate, Richard. So once
you've discussed this with Deborah, you should still do what any
red-blooded American male would do: Whatever your wife says.

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