Car Talk

Q. I live in Albany, N.Y., and I own a 2009 Dodge Journey, all-wheel drive, with 19-inch wheels and tires. I didn’t realize it at the time, but getting these optional huge wheels has made it impossible to find winter tires. So I have to buy another set of smaller, 17-inch wheels to put my winter tires on. Here’s my question: The car has a tire-pressure monitoring system that tells me when the pressure is low in one of the tires. Do I have to buy new tire-pressure sensors for each of these new wheels, or can I get by without them? Or can I buy a cheaper, aftermarket system?

RAY: Those 19-inch wheels looked really great in the showroom, didn’t they? What you don’t realize when you buy monstrous wheels is that (A) it’s going to cost you a fortune to buy replacement or snow tires for them, and (B) you’re going to feel every cigarette butt in the road.

TOM: We understand your desire to save money, especially since you already spent $600 upgrading to those 19-inch wheels. But we can’t recommend that you save cash by disabling the tire-pressure monitoring system.

RAY: The sensors can be expensive. For some cars, they’re several hundred dollars each! In that case, an aftermarket system may make sense. But in your case, the original Dodge sensors are not that pricey.

TOM: At the dealership, they’ll cost you about 50 bucks each. Figure on spending about $300 to buy four of them and have them installed and programmed on your new set of wheels (the computer has to be told which particular wheel each sensor is monitoring).

RAY: You have to do it. Most people think that having a tire with low pressure is no big deal. But it can create a cascade of problems.

TOM: When a tire’s pressure falls, that tire’s sidewall flexes more than it should. If nothing else, that compromises the car’s handling.

RAY: And if you keep driving on an underinflated tire, the deformation can lead to an intense buildup of heat. Excessive heat can lead to belt separation and a “catastrophic” tire failure—better known as a blowout.

TOM: And if you think driving on 19-inch tires is exciting, wait ’til you have a blowout and go asphalt over teakettle into a nearby pine forest.

Q. I need your help! My significant other has been placing a blanket over her engine for years now. During spells of extreme Minnesota winter weather, she’ll go out and throw the blanket over the engine and close the hood. She’s done this on a variety of vehicles, and the only constants are that the engine has to be pre-warmed, and there has to be a threat of bad weather the next morning. Is this actually doing anything to help the car?

RAY: Well, it works for horses.

TOM: Right. The difference is that horses create heat, and the blanket helps retain the heat they create. Once an engine stops running, it’s no longer creating any heat. It’s only losing heat.

RAY: So, any insulation — a blanket included — can help slow the loss of heat. But can it prevent an engine from losing all of its heat for, say eight or 10 hours, overnight? Seems unlikely.

TOM: An engine takes several hours to get completely cold. But the blanket covers only the top of the engine. Remember, the cold air has full access to the engine from underneath, too. So I suppose if you really wanted to try to retain some engine heat, you could surround the engine on all sides with insulation.

RAY: We call that “a garage.”

TOM: A better approach is to install a block heater. Or a block heater AND a blanket. A block heater is a small heating element that’s inserted into one of your radiator hoses. It gets plugged into an electrical outlet at night — or into a timer — and keeps your car’s coolant from dropping below a certain temperature. That, in turn, keeps the oil from “going molasses on you.”

RAY: A block heater not only makes the engine easier to start on very cold mornings, but since your cabin heat comes from the coolant, it warms your tootsies faster, too.

TOM: And it saves your significant other from making those late-night trips out to the driveway in her nightgown to tuck in the car for the night. Make it her next birthday present.

Got a question about cars? Write to Click and Clack in care of this newspaper, or e-mail them by visiting the Car Talk Web site at www.cartalk.com.