Ways to ease chill of winter on mpg
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 EPA 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 3-4 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.
Here are 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 has time to 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 up faster while being driven.
–Plug-in hybrids benefit from preheating while still plugged in, before you start 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.
DODGING POTHOLES: This winter's been rough on tires and wheels.
Conditions will probably get worse, said Chris Lynch, owner of Wetmore's Tire and Auto Repair in Ferndale, Mich. Spring thaws are likely undermine already 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 in – 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.
"Tires lose about one pound of air a month," Edmonds said. "If the inner liner is compromised, it'll be greater than that."
Everyone should check their tires' pressure at least that frequently. Correct pressure improves your fuel economy and reduces the likelihood the sidewalls will flatten and damage the inner liner when you hit a pothole, said Dave Cowger, General Motors' top tire expert.
There's one other option, Edmonds said: minus-sizing. Some people buy a tire and wheel an inch or two smaller than what came on the car and get tires with taller sidewalls.
"Switching from a 245/50/18 tire to a 235/60/17 can give you an inch more sidewall to protect the tire," he said.
It's very important that anyone who does that makes sure the new tires have the same diameter as the manufacturer specified. A different tire diameter could foul up the vehicle's antilock brakes, stability control, odometer and other important features.
Drivers who don't want to go that far should remember that snow tires with cheap steel wheels improve safety and reduce the cost of a ruined wheel. Lynch says a steel wheel can cost $40 to $70, compared with hundreds for fancy aluminum.
ABOUT THE WRITER
Mark Phelan is the Detroit Free Press auto critic. He can be reached at firstname.lastname@example.org.
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