Dear Tom and Ray:

I am interested in purchasing a new car; I currently drive an Isuzu Rodeo. I am interested in hybrid technology and, in particular, the Ford Escape Hybrid or Toyota Highlander Hybrid that are coming out in the next year. Based on my understanding of the technology, the braking is what charges the battery. I have heard that hybrids are really good for short trips, but that if I wanted to drive my Escape Hybrid to Lake Tahoe from San Francisco (about four hours), after about two hours or so the car would go slower and slower, because it is running on the battery on the freeway. And because I would not be braking frequently, the battery would not be charging. Bottom line: Are hybrids good for longer drives and multiple hours on the freeway, or would I be disappointed in the performance? Thanks. -- Ramona

RAY: I doubt you'd be disappointed by the performance, Ramona. You've been given some incorrect information.

TOM: While regenerative braking (taking the change in velocity that's created when the car slows down and turning it into electricity) is one way a hybrid charges its battery, it's not the only way. In fact, it's not even the primary way.

RAY: The gasoline engine is the main source of electricity for the battery pack. So, anytime you're driving -- highway or city -- the battery can be charged up if it needs charging, and it should never run low.

TOM: On the highway -- no matter how long a trip -- the gasoline engine and electric motor would work together as necessary, with no loss of power over time. So, there's nothing to worry about in that regard.

RAY: Now, you might have heard someone say that "hybrids do better around town than on the highway." That's true if you're talking about gas mileage. Because a hybrid makes more extensive use of the electric motor in stop-and-go driving, that's where you get the best gas mileage.

TOM: For example, the hybrid Toyota Prius is EPA rated at 60 miles per gallon in the city, and a measly 51 on the highway -- the exact opposite of most cars we're used to. Even if those figures are a bit optimistic in real life, the ratio is correct, since you need more help from the gasoline engine on the highway than you do around town.

RAY: So, on the highway, you're simply not taking maximum advantage of the hybrid's fuel-saving capacity. But to answer your question, it will run all day for you, Ramona. You won't be limping into Tahoe with dim headlights, looking for a convenience store so you can buy it out of D-cells.

TOM: By the way, if anyone is interested in reading more about hybrids, we have a whole section devoted to them on our Web site, www.cartalk.com.