Expert Q&A: Cars

Is it wise to inflate tires to 110 percent of the recommended pressure?

Alan Paulding
Plymouth, MA

Inflating your tires to a higher pressure than the automaker's recommendation can reduce heat buildup and decrease rolling resistance, resulting in slightly better fuel economy. But it can reduce the tire's grip on the road and decrease ride comfort. Overinflating can also make the tread wear unevenly, shortening the life of the tire. For maximum performance and safety, keep your tires at the auto manufacturer's recommended pressure, which is usually found on a placard in a doorjamb, not on the tire's sidewall.

Was the new-car protection package I bought for corrosion, paint, sound deadening, and such a waste of money?

Meridith Tusha
Omaha, NE

Yes. New cars don't need added rust protection because they're usually treated at the factory. You can apply paint and interior protection yourself with off-the-shelf products (or hire an auto detailer, who will probably charge less than a dealer). Sound-deadening undercoating adds weight to the car and can decrease mileage.

Do I need to pay the dealer-prep fee in the contract for the new car I'm buying?

John Bickel
Golden, CO

Refuse to pay this fee, which reimburses the dealer for preparing the vehicle for you. Dealer prep, often indicated as a "pre-delivery service" fee, usually includes removing coverings that protect the vehicle during shipping and cleaning and inspecting the vehicle. Most automakers already pay dealers for that work; you shouldn't pay it again.

Why did my car's gas mileage drop when I started using E10 fuel?

Harvey Fox
Schenectady, NY

Ethanol has a lower energy content than gasoline, so your fuel economy with E10-10 percent ethanol, 90 percent gasoline—will be lower than with 100 percent gasoline. Our test vehicles usually run on 100 percent gasoline. When we drove a Chevrolet Tahoe flex-fuel SUV using E85, mileage dropped 27 percent compared with gasoline. So using E10 should result in about a 3 percent drop in gas mileage.

My Toyota's owner's manual calls for a special pink antifreeze. Is there any risk of corrosion if I use a green antifreeze?

Jack Extract
Freeport, NY

Toyota and some other automakers use a special long-life coolant to prevent corrosion of aluminum parts; it requires flushing only every 100,000 miles. Conventional antifreeze, typically green, doesn't protect aluminum as well and needs flushing every 60,000 miles. Prestone and other brands sell formulas, such as the orange Zerex Dex-Cool, compatible with the automakers', usually at a lower cost.

More questions and their answers can be found in our Cars blog.

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