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THE CAR DOCTOR

Winter mileage drops, but not this much

Plus: When antifreeze freezes, run-flat durability

By John Paul
Boston.com Columnist / January 26, 2009

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Q. My 2006 Toyota Matrix, with a standard transmission, gets worse mileage in the cold, down by about five miles per gallon. Is there anything I can do to improve the mileage in winter?

A. In winter weather you can always expect a drop in fuel economy. This is due to the formulation of "winter" gasoline. It is not unusual to see up to a five percent drop in fuel economy due to this cold weather formulation. It is this special formulation that allows for easier starting as the temperatures dip. Add this to slightly longer warm-up times, lower tire pressure, and thicker fluids in the other components of the car, and it is easy to see how mileage will be lower. That said, it looks like you are seeing a 20 percent drop in fuel economy, which to me seems excessive. At this point it would make sense to have an overall evaluation of the car and request a careful fuel mileage test.

Q. In one of your columns, you once said there were no stupid questions; my question may test this. Will antifreeze freeze if you don't add the right amount of water?

A. Typical ethylene glycol antifreeze when mixed in a 50 percent ratio of water and antifreeze will protect against freezing to 35 degrees below zero. Add more antifreeze and the protection point gets lower, but only up to 70 percent antifreeze. Over this percentage the mixture loses it ability to protect against freezing. Straight antifreeze will freeze at seven degrees above zero. Great question!

Q. I will be purchasing a certified pre-owned 2007 BMW 328xi with 22,000 miles. I've heard some nasty things about how run-flats wear out a lot faster than regular tires. Can you comment on this?

A. I have seen run-flat tires on some cars last as little as 12,000 miles. The various BMW forums seem to show that 20,000 to 25,000 miles is closer to an average. You could consider replacing the run-flat tires with a conventional design, but that could be a bit tricky since I don't believe there is room for a full-size spare tire or jack.

Q. I have a 1989 Volvo 240 sedan with a cracked/leaking engine block. Yes, my coolant-to-water ratio was off and we had some very unusual freezing temperatures in my city. Anyway, as I am not in a position to purchase another car, nor afford a new engine, I was wondering if you could give me some guidance for searching for a rebuilt engine. Or is it possible to safely patch (with JB Weld) the leaks?

A. A technician may be able to determine if the problem is a cracked block, leaking head gasket, or cracked head. As far as patching the crack with a product like JB Weld, as good as this product is, it may provide a temporary solution to an external crack, but it won't work for an internal leak. Considering the car is 20 years old, a used engine may be a reasonable solution.

Q. The left blinker (directional) in my 2004 Dodge Caravan started to blink very fast. The right seems to be working normally. The bulbs seem to be working, just more rapidly. Is it the bulbs, fuse, or what?

A. Whenever turn signal bulbs blink rapidly it is usually an indication of a faulty bulb, socket, or in some cases a wiring problem. When checking the bulbs don't overlook the small running light bulbs. In some cars if one of these bulbs is out it will have the same effect you have described.

Q. Is VW delaying the release of the 2009 Passat and Passat wagon with the V-6 and 4motion? When I go to the VW website or any dealer sites, the only model they mention is the "Komfort" which only has the 2.0 liter turbo four-cylinder and no all-wheel drive. Do you have any information on these cars?

A. According to Steve Keyes, the General Manager of Public Relation for Volkswagen, there will be no 4motion Passat for the upcoming year. Perhaps they want to further separate Volkswagen from Audi.

John Paul is the public affairs manager for AAA Southern New England. He can be reached at jpaul@aaasne.com.