Is a V-6 engine better for highway driving?

Dear Car Talk

Dear Car Talk | Sep 01, 2002

Dear Tom and Ray:

My wife and I are having a disagreement. My wife does a lot of highway driving, and she insists that she needs a V-6 engine on our new car. My opinion is that a four-cylinder engine is sufficient for the highway. What do you think? -- Craig

RAY: Well, it really depends on the car, Craig. It depends on the weight of the car, the size of the cylinders and the technology of the engine, among other things.

TOM: For example, when the Dodge Caravan first came out, it was available with an old-fashioned 2.2-liter four-cylinder engine. And it was a complete dog (as we say in the business). In fact, my brother once got in trouble with Chrysler for saying that the four-cylinder engine was responsible for the Caravan being a seven-passenger vehicle. (Because when you came to a hill, you needed six people to get out and push!)

RAY: On the other hand, we've recently driven the new Toyota Camry and the new Nissan Altima. Both test cars had four-cylinder engines, and until we looked under the hood, we thought we were driving cars with V-6s.

TOM: Clearly, your wife is not happy about the power in the car she drives now. She must feel that it's underpowered when she's getting on the highway or trying to pass. That suggests she needs a more responsive, more powerful car. But that doesn't necessarily mean she needs a V-6.

RAY: If you want a rule of thumb, you can figure out the power-to-weight ratio for the cars you're interested in. For instance, the Altima we drove with the four-cylinder engine has about 6 horsepower for every 100 pounds of vehicle weight. And it was more than adequate on the highway. In fact, it was downright fast.

TOM: Compare that with the current base Dodge Caravan's 2.4-liter four-cylinder engine, which struggles on the highway. The Caravan has only 3.8hp per hundred pounds!

RAY: And by the way, that's the five-passenger Caravan, so you only have four people to get out and push.

TOM: To figure out the ratio yourself, you take the horsepower of the engine and divide it by the weight of the car in pounds, then multiply by 100.

RAY: Of course, your wife needs to drive any perspective car on the highway to see for herself, but if you want a rough guideline, anything in the neighborhood of 5hp to 6hp per 100 pounds should be worth considering, regardless of whether it has four or six cylinders.

TOM: And trust us, Craig -- you want her to feel satisfied with the power. Because if she's not, she'll stomp on the pedal and curse the thing and beat the hell out of it, which means you'll be buying another four-cylinder car in a couple of years. And four plus four equals eight. So you're better off just buying six now, right?

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