Q: I'm in the process of getting a divorce, and am getting the four-year-old minivan. I'm wondering what your thoughts are about whether, given the price of gas, I should trade it in and begin making payments on a hybrid.

A: It's almost never cost effective to replace an older paid-for or almost-paid-for vehicle with a new one. Naturally, when a vehicle gets to be six or eight years old there can be repairs that begin to add up pretty fast. But you're not there yet.

Conventional wisdom has held that if you buy a new hybrid (which will generally cost $2,000 to $8,000 more than a conventional model), it will take four-to-six years before you begin to realize any financial benefit from having not purchased a traditional fuel burner.

Now remember, we're talking one new car versus another new car, and that takes years for the balance to tip.

I offer that little piece of information merely to give you some sense of what the pencil-to-paper experts have come up with regarding the long-term offset of buying a hybrid. When you're talking about keeping an older vehicle versus buying a new hybrid, it would be a really, really, really long time.

Naturally, there are hundreds of variables. What may make the most sense for your situation is to investigate the possibility of buying a smaller two-year-old conventionally powered vehicle - you can find many that will give you 28 miles or more per gallon.

But before you cut the deal, make sure you have also taken into account the probable increase in your insurance rates (you'll usually pay more when you have a later-model car) and factor in the cost of sales tax and registration.

Reader comments: I responded recently to a reader who wondered whether the low-slung Toyota Prius hybrid-powered sedan tends to bottom out in certain driving situations. And the answer is that indeed there have been reports of underside scraping, particularly when going over speed bumps (but that is not the only circumstance that scratches, grinds and rips the underbelly).

A few readers weighed in with their own stories of damage and destruction among low-riding hybrids. Here's one: "I bought a Honda Civic Hybrid three years ago and was appalled the first time I parked it in a lot. As I pulled forward to the cement stop/curb, the front end scraped against it.

Other cars clear them, but not mine... and the underside of the front fender has shredded. The low body is also a problem in heavy rains. If I have to drive through six inches of water it causes the plastic undercover liner to detach and drag (from the pressure of the water since the shield isn't held with screws or bolts but is just tucked in)." It's always good to know these things. So thanks, readers.

Another reader wrote in regarding my answer to a person who asked if it's worth the extra money to put nitrogen in tires instead of run-of-the-mill air out of the air pump. He agreed with all my points that there seems to be no valid rationale for paying $3 to $6 per tire to pump in nitrogen. But he also gave me a little tweak, adding,

"What you failed to point out, and what few people seem to realize, is that the very air tires are already inflated with is already about 80 percent nitrogen. So even if nitrogen was the magical gas that improved gas mileage (and it doesn't) you're already getting 80 percent of the benefit for free."