Driving 25 mph in fourth...

Dear Car Talk

Dear Car Talk | Oct 01, 1991

Dear Tom and Ray:

My sister tried to tell me it was OK to drive my Geo Metro without engaging the clutch when I let her take it for a spin. Luckily for me, I had already read about how bad that is in your column; luckily for my sister, she drives an automatic. Now my boyfriend is trying to tell me its perfectly OK to drive my car in fourth gear at 25 mph. After my sister's advice, I told him I'm writing to you first. He said my car wasn't ready to stall out, and as long as he didn't accelerate too quickly, it was fine. He claims that driving my car this way is good on gas mileage and good on the engine. I mentioned his theory at work, and everybody there had a different opinion. What's the scoop?

RAY: Excellent question, Patty. And believe it or not, your boyfriend is right.

TOM: The engine actually takes care of itself in this regard. If you try to make the engine do something it can't do--like drive in a gear that's too high--the engine will let you know there's a problem. It does that by making the whole car shake like one of those cheap motel beds that takes quarters.

RAY: If you drive with the engine shaking like that, you're "lugging" the engine. And over time, lugging the engine will ruin it. So when?ever you notice that shaking, that's your signal to shift into a lower gear right away. But as long as the engine is running smoothly, you're doing fine.

TOM: Your boyfriend is also right that it's not merely a question of how fast you're going. The driving conditions have to be considered, too. Your engine may run smoothly at 25 mph in fourth gear on a nice flat road. But if you tried to climb a hill at that speed in fourth gear, you'd definitely lug the engine. The same would be true if you tried to accelerate quickly in fourth gear from 25 mph.

RAY: So the scoop is this, Patty: There are two things you should listen to, your boyfriend (in this case only), and your engine (all the time).

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