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Ease chill of winter on mpg

| Saturday, March 1, 2014, 12:01 a.m.

Cold weather can reduce your fuel economy drastically, but there are ways to mitigate the impact.

A cold engine, driveline and battery pack have more friction, use more fuel and reduce the efficiency of hybrids' regenerative braking, said Brian West, a development engineer at Oak Ridge National Laboratory in Tennessee.

West compared fuel consumption on the 20-degree F and 75-degree F cycles of the test the Environmental Protection Agency uses for fuel economy ratings.

The fuel economy of conventional gasoline vehicles fell 12 percent to 22 percent, with the biggest decrease on short trips of 3 to 4 miles. Hybrids fell 31 percent to 34 percent.

“The majority of the hit is from more viscous fluids before the drivetrain warms to its optimum temperature,” West said. “The hit on hybrid fuel economy is more severe because cold batteries are less efficient recapturing energy from braking.

“The impact is greater for both types of vehicles on shorter trips” that don't give fluids and batteries time to reach operating temperature.

Some cold weather tips from FuelEconomy.gov:

• Park in the warmest available spot. An enclosed garage is best.

• Combine several errands into one trip so the drivetrain can warm up.

• Don't use seat heaters and defrosters longer than necessary.

• Don't let your car sit idling to warm up. The most efficient technique is running the engine for 30 seconds, then driving off gently. The engine warms faster while being driven.

• Plug-in hybrids benefit from preheating while still plugged in, before driving.

• Plug-in hybrids are more efficient if you use the seat and steering wheel heaters more than heated air. It's fine to keep them running all the time in a plug-in.

• Keep your tires properly inflated.

Tires vs. potholes

This winter's been rough on tires and wheels.

Conditions will likely get worse, said Chris Lynch, owner of Wetmore's Tire and Auto Repair in Ferndale, Mich. Spring thaws are likely to undermine weakened roads and open new potholes.

Bent wheels are more common than blown tires, but there are plenty of both this year.

Catastrophic blowouts are easy to recognize, but many drivers have tire damage they never realize was caused by a pothole, said Matt Edmonds, vice president of online retailer the Tire Rack.

The tire's inner liner — the part that holds the air — gets pinched between the road and the wheel when a car hits a pothole. That tears the lining, creating a leak that causes a blister on the sidewall of the tire. You might never notice the blister because it shows up only when the tire is hot from driving and the air inside expands. Just to make it tougher, many blisters are hidden from view on the tire's inner sidewall.

“A torn inner liner is not repairable,” Edmonds said. “It can lead to tire failure months later when the tire gets hot in the summer.”

He recommends monitoring tire pressure to see whether there's a slow leak, then having a tire shop check for damage, including the easy-to-overlook damaged liner.

Mark Phelan is the Detroit Free Press auto critic. He can be reached at mmphelan@freepress.com.

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