OnStar data shows mileage of drivers in identical cars can vary by 75 percent!

With Grand Rapids residents paying an average of $1 more per gallon of gasoline than a year ago, many drivers are looking for ways to improve their fuel economy during the Memorial Day weekend – the unofficial start of the summer driving season.

To demonstrate 10 common mistakes drivers make that affect their fuel economy, we recently partnered with Chevrolet to drive two identical compact cars on a typical workday commute. The results show that sweating the small stuff could save you as much as $100 a month at the pump.

For the drive, GM fuel-economy engineers Ann Wenzlick and Beth Nunning drove identical Chevrolet Cruze LTs, which the EPA estimates get 27 mpg city, and 36 mpg highway. For the route, they drove both cars for 20 minutes, including city and highway driving as well as a coffee stop.

Wenzlick averaged 37 miles per gallon using efficient driving habits in a properly maintained Cruze. Driving inefficiently and ignoring common maintenance, Nunning managed only 21 miles per gallon.

The difference means Beth would get 250 fewer miles per tank of gas, while Ann would save $100 a month – or $1,200 a year – assuming 15,000 miles and $4 a gallon for gas.

Here are five things Ann did to drive more efficiently in her Cruze:

1. Get out of the drive-through lane. “While Beth waited in the drive-through with her car running, I shut off the engine and went inside for my morning coffee. Idling for 15 minutes burns through an average of a quarter of a gallon – adding another $1 to the cost of your latte.”
2. Take it easy. “In the city, I accelerated smoothly while Beth demonstrated one of the most common mistakes we see on the road, jumping on the gas at every light, only to hit the brakes as she caught up with the traffic ahead. Such aggressive driving isn’t going to get you home any faster, while driving smoothly can improve your mileage by 20 percent.”
3. Driving 70, not 80. “On the highway, I drove 70, compared to Beth’s 80. Again, a 10-mph difference likely won’t add much time to your daily commute, but it will save you up to four miles per gallon on the highway.”
4. Use cruise control. “I tried to maintain a constant speed during our drive, while Beth’s fluctuated with traffic. Try using cruise control when possible, and maintaining a constant speed over time, which is much more efficient than speeding up and slowing down over and over again.”
5. Roll up the windows. “One of the most common questions we get is ‘is it better to drive with the A/C on, or off?’ At slower speeds, turning off the air conditioning can save you a little, but I always roll up the windows on the highway. Beth was driving with her windows down, and the increased air pressure acted like a parachute trying to slow her down – consuming much more energy than air conditioning ever will.”

Five Vehicle Mistakes That Hurt MPG:

Here are things that contributed to Beth’s poor fuel economy:

1. Low tire pressure. “All four tires on my car were five pounds under their recommended air pressure. That’s not enough to change how the Cruze drives, but it does make the engine work much harder to turn the wheels. Check your tires at least once a month, as a tire that is 10 pounds under pressure can cut your fuel efficiency by more than 3 percent.”
2. Using roof ornaments. “To show support for my favorite sports team, I put up window flags on my Cruze for every home game. But when the team is on the road, the flags will come down. At highway speeds, up to a third of your fuel is used to overcome wind resistance, so even small changes to your vehicle’s aerodynamics will have a big impact on fuel economy. “
3. Carrying extra junk in the trunk. “I had six bags of water-softener salt I bought on sale at the hardware store in the trunk. But according to EPA estimates, every 100 pounds of weight can reduce fuel economy by 2 percent. While I saved at the checkout, that 240 pounds of salt added almost 5 percent to my fuel costs for the trip.”
4. Ignoring the “check engine” light. “I called OnStar to run a remote diagnostics check on my Cruze, because the check engine light was on. Turns out the light was on because the gas cap was loose. More serious engine problems can cut your fuel economy by up to 40 percent.”
5. Not bundling errands. “An engine at operating temperature is up to 50 percent more efficient than a cold engine. So when possible, it’s much better to run five errands in an afternoon than running one errand every day of the week.

What are you doing to save at the pump? Any tips on where to find the best gas prices?!