CAR TALK\Save gas, and your foot, by using the cruise control.

Byline: Tom and Ray Magliozzi 

Dear Tom and Ray: I recently purchased a '95 Ford Probe. Cars certainly have come a long way since I last bought one 13 years ago. I'm new to cruise control, but it didn't take very long to be sold on it. However, I have a couple of questions.

First, several people have told me that you get better fuel economy while using cruise control. Really? If so, why?

Second, if I know I'm going to be off cruise control for a period of time (for example, when I'm going through a town), does it matter if I turn off the "main" cruise control switch on the dashboard? Is there any difference between having it actually "off" and just "not operating at the moment"?

- Rob

Ray: First of all, Rob, congratulations on entering the modern era. Cars HAVE come a long way in the last couple of decades. Anyone who questions that need only look at my brother's Dodge Dart. How's the cruise control on that baby, Tommy?

Tom: You mean the cement block I rest on the gas pedal?

Ray: You probably do get better mileage with cruise control if you're driving on long stretches of reasonably flat roads. That's because cruise control keeps you at a constant speed.

Tom: It takes more gas to speed up than it does to maintain an even speed. And when most of us drive, we inadvertently slow down, speed up, slow down, etc. It takes a lot of concentration to stay at a steady speed without cruise control. But with it, it's no problem at all.

Ray: By the way, for you teen-agers reading the paper today, when we say you get better mileage when traveling at a steady speed, we mean a reasonable steady speed. You're not going to get better mileage driving at a constant 80 mph than you would by fluctuating between 50 and 60.

Tom: But I wouldn't use the cruise control just to save gas. The benefit is probably marginal. The real reason to use cruise control is so you don't get cramps in your right leg Ray: And you SHOULD turn off the "main" cruise control switch on the dashboard when you're not going to be using it for a while. The "set" switch is on the steering wheel or stalk of most cars, which is great because it's very convenient. But it's also easy to engage it accidentally. That's why there's a harder-to-reach "main" switch on the dashboard. So, yes, turn it off for safety when you're not on the highway to prevent accidental engagement.

Dear Tom and Ray: I recently purchased an '83 Honda Civic. One issue of "The Consumer Guide Used Car Book" says "valves must be adjusted every 15,000 miles to prevent engine woes." Later issues of the book do not mention this. What is your opinion?

- Amy

Tom: It won't do any harm to adjust the valves every 15,000, Amy. But based on my experience with these cars, I'd say every 30,000 miles is fine.

Ray: But more important, I would be sure to change the timing belt at least every 60,000 miles (and the water pump, too, which is driven by the timing belt). This is one of the motors that has a lovely habit of crushing its own valves when the timing belt breaks - often ruining the engine.

Tom: And once that happens, adjusting the valves at any interval will be like a television set on a honeymoon - unnecessary.