Q. I own a 2005 Nissan Pathfinder V-6 with 32,000 miles on it. It runs great, but gets about 18 miles per gallon. About 75 percent of our driving is on the highway. Because I plan to keep this vehicle for a while, I would like to try to squeeze a few more miles per gallon from it. I am sure that there are a lot of people who have SUVs but cannot trade them due to the trade-in values right now. I wanted to know how to improve the mileage on this type of vehicle. I was thinking of the following, and wanted to know if it is worth it: switch to a low-restriction K & N air filter. I have read claims that this type of filter can return up to 4 more mpg, using synthetic oil and switching to a less aggressive tire. Do you have any specific recommendations? Will these individually, or taken together, give me more miles per gallon? If so, how much?

A. All of these improvements will help increase your vehicle’s mileage. Synthetic oil, proper tire inflation, and preventive maintenance will all help. But, that said, don’t expect mileage miracles. All of these improvements may increase your vehicle’s overall fuel economy by perhaps 5 percent. But it has been my experience that the best method to improve your vehicle’s fuel economy involves looking at your own driving habits. Hard acceleration, speeding, and excessive idling are the practices that significantly reduce fuel economy.

Electronic key hassles

Q. I’m hoping that you or your readers can help me. I have a 1999 Mazda B3000 pickup truck that requires an electronic key with a programmed computer chip. I only have one key, so I bought four blank copies from Mazda and took them around to all the Mazda dealerships and several large locksmiths in Rhode Island. All tried, and charged me, but none could program any of the keys. The truck has manual door locks and hand crank windows. I do not understand why Mazda would put an ignition on this model truck that requires a $200 programmed key. Do you know of anyway to bypass the requirement for the programmed key either by disabling the software in the truck or changing out the ignition? I am afraid to try as it might disable the truck permanently.

A. The way I understand it is that you need the two original keys to program a spare key. With the two original keys you can add up to six additional spare keys. If you are missing one key, you need to start over from scratch with two new keys. The procedure calls for erasing the computer’s memory and programming the two new keys. When electronics stores install a remote car starter they bypass the anti-theft feature. This method may work, but will probably be more expensive than programming new keys.

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