What's the best way to warm up a car? Lunch hangs in the balance.

Dear Car Talk

Dear Car Talk | Aug 01, 1995

Dear Tom and Ray:

It has recently been brought to my attention that a certain co-worker of mine has depleted his reserve of brain cells. You see, he is a product of the sixties, and you know what that means! He is under the miguided assumption that starting a car to warm it up is harmful to the engine. His specific objection is that the oil does not circulate until the tires move. I, being a product of the enlightened and technologically sophisticated eighties, believe there is no harm done. Lunch hangs in the balance. Tofu and watercress for him -- double cheeseburger for me. P.S. He also thinks polyester is cool!

TOM: What's wrong with polyester?? C'mon, Nat. I'm a product of the sixties, too.

RAY: Yeah. The 1860's!

TOM: We're going to have to declare this contest a tie, Nat. I admit that your co-worker is way out there with his "tire related oil circulation" theory. He probably smoked a few too many CV joints before he came up with that one. But for his time, he is technically correct. And for your time, you are technically correct, Nat.

RAY: Here's why. Back in the sixties, all cars were carbureted. And when you started a carbureted engine, it dumped a very rich mixture of fuel into the cylinders--that means a lot of gas and not much air. And if you just let it "warm up" and idle like that, with all that fuel pouring in there, you'd dilute your oil and build up carbon crud all over everything. So on carbureted cars, excessive warm ups were harmful.

TOM: Moreover, on carbureted cars of the late seventies and eighties, running under fuel-rich conditions also ruined the catalytic converter. So until very recently, it really was a lousy thing to do.

RAY: By the late eighties, however, most cars were fuel injected. So the fuel-air mixture was carefully metered by computer, and excess fuel wasn't allowed to pour into the cylinders. So on fuel injected cars, no harm is done to the car by warming it up.

TOM: Unless you factor in the gas you're wasting and the pollution you're creating. But being a product of the eighties, Nat, that probably doesn't concern you as much as, say, when the next version of Nintendo is coming out.

RAY: Now, now. Nat is technically correct. For modern (that is, fuel injected cars), warming it up does not do any harm to the car itself. So, you see, you're both right.

TOM: So here's my ruling. Since you are technically correct in the eighties, Nat, your buddy has to buy you lunch. But since you have shown insufficient respect for your elders (even if they have no remaining brain cells), the lunch he buys you can be a tofu and watercress sandwich...with a side of beet juice.

RAY: And since your buddy was technically correct in the sixties (even though he is sartorially incorrect in the nineties), you have to buy him lunch. But since he came up with this wacko oil-doesn't-circulate-til-the-tires-move theory and embarrassed eveyone else who grew up in the sixties, you can buy him a bacon double cheeseburger... with a side of sausage.

TOM: Good luck, guys. And write to us again the next time you disagree. This was fun.

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