The summer driving season is here and most of us will be heading out for a much needed vacation. I'll be off to Rehoboth beach soon. Along the way, I'll be informing (or from his POV, nagging) my boyfriend of how to get the most out of his mileage. Hopefully you can utilize this information to increase the your gas efficiency as well.
This diary is for personal car usage. Carpooling, public transit, bikes, and walking work a lot better than the tips below in extending your gas tank. But if your like most Americans and use your car for mostly solo trips, then you should find some use for these suggestions. This also won't cover hypermiling. I find that too dangerous and some techniques are illegal as well.
Your car's fuel economy depends heavily on how you drive and how forces such as drag and inertia interact with your car. The other major factors are how well you care for your car.
The following cost savings are based on an assumed fuel price of $3.65/gallon.
1. Drive at 55mph (or slower) - That MPG label that for your car is based on it's speed at 55mph. Cars typically have a sweet zone of working from 25-55mph. When you hit 60 mph, you quickly loose out. On average, your car gets:
- 3% less efficient at 60 mph
- 8% less efficient at 65 mph
- 17% less efficient at 70 mph
- 23% less efficient at 75 mph
- 28% less efficient at 80 mph
As you go faster, you increase the amount of air drag on your car, thus lowering your efficiency.
Back during the oil crisis of the 1970s, Congress passed a National Maximum Speed Law mandating a max speed of 55mph nationwide. Foreign oil accounted for 36% of our energy use before the national speed limit took effect, but in 1985, foreign oil made up just 28% of U.S. energy consumption, a record low. The law was soon revamped to 65 mph, then repealed in 1995. We now import about 69% of our oil, most of it going to our transportation and lead feet.
Fuel Economy Benefit: 7–23%
Equivalent Gasoline Savings: $0.26–$0.87/gallon
Observing the speed limit is also safer.
2. Keep your speed steady - Fast acceleration and deceleration not only decreases your efficency, it wears on your brakes, engine, and transmission. From fueleconomy.gov:
Weaving in and out of traffic, not using the highest gear, jumping on and off the throttle, and generally not keeping a steady-state speed are also shortcuts to the nearest gas station.The numbers above were the combined effect of higher speeds and aggressive driving. Still, burning rubber when the light goes green or slamming the breaks at each stop sign causes your car a lot of stress to overcome its inertia. Slow and steady win the race.
On the highway, our drivers returned a high average MPG of 24.4, and a low of just 17. That's a 43% difference! Here efficient driving works out to be an extra 140 miles of range per 19-gallon tankful.
Fuel Economy Benefit: 5–33%
Equivalent Gasoline Savings: $0.19–$1.25/gallon
3. Avoid idling for more than 30 seconds - The worst mileage a car can get is 0 miles per gallon, which occurs when it idles. Idling for long periods of time, whether waiting to pick up kids at school, at a rail road crossing, or what not, it consumes gas that could be saved by simply turning off the engine. Restarting an engine uses about the same amount of gas as idling for 30 seconds (for some newer models its 10 seconds). When idling, shut off the engine.
Fuel Cost Savings: $0.01–$0.03/min. (AC off), $0.02–$0.04/min. (AC on)
4. Plan your route for multiple trips- When you combine multiple trips you typically lower the distance you are driving and also allow your engine to operate at a more efficient warmer temperature.
Fuel Cost Savings: varies
Please note: Modern engines don't need much time to warm up. The engine actually warms up more quickly once the car is operating, and will stay warm after stopping.
5. Clean your car - Extra weight equals extra inertia your car has to overcome.
Fuel Economy Benefit: 1–2%/100 lbs
Equivalent Gasoline Savings: $0.04–$0.08/gallon
6. Streamline your car - Unless you regularly use that bike or luggage rack, take them off. The more aerodynamic your car is, the less drag it will produce. Less drag equals to less gas needed to overcome it.
Fuel Economy Benefit: 5% for a loaded roof rack
Equivalent Gasoline Savings: $0.19/gallon
7. Properly maintain your car - When the check engine light comes on, your fuel economy usually takes a hit.
Keep Your Engine Properly Tuned
Fixing a car that is noticeably out of tune or has failed an emissions test can improve its gas mileage by an average of 4%, though results vary based on the kind of repair and how well it is done.
Fixing a serious maintenance problem, such as a faulty oxygen sensor, can improve your mileage by as much as 40%.
Fuel Economy Benefit: 4%
Equivalent Gasoline Savings: $0.15/gallon
Keep Tires Properly Inflated
You can improve your gas mileage by up to 3.3% by keeping your tires inflated to the proper pressure. Under-inflated tires can lower gas mileage by 0.3% for every 1 psi drop in pressure of all four tires. Properly inflated tires are safer and last longer.
The proper tire pressure for your vehicle is usually found on a sticker in the driver's side door jamb or the glove box and in your owner's manual. Do not use the maximum pressure printed on the tire's sidewall.
Fuel Economy Benefit: Up to 3%
Equivalent Gasoline Savings: Up to $0.11/gallon
There are also tires available designed to increase your fuel efficiency, though savings have been found to be small overall.
Use the Recommended Grade of Motor Oil
Using 10W-30 motor oil in an engine designed to use 5W-30 can lower your gas mileage by 1–2%. Using 5W-30 in an engine designed for 5W-20 can lower your gas mileage by 1–1.5%. Also, look for motor oil that says "Energy Conserving" on the API performance symbol to be sure it contains friction-reducing additives.
Fuel Economy Benefit: 1–2%
Equivalent Gasoline Savings: $0.04–$0.08/gallon
8. A/C vs Windows down - Now this measure has been debated back and forth for a good while. Some people/websites claim A/C has minimal impact on mileage, others claim the opposite. I've told others that if you are going below 45mph, open your windows. Above 45mph, then A/C is more cost efficient since your engine would have to work harder to overcome the drag from the air. That seems to be the same conlusion according to MythBusters:
Once the safety inspector intervened, it was no longer a seven-hour marathon, it was a bit slower (45mph instead of 55mph), and a lot shorter (only 5 gallons each).9. Fuel additives don't work - Be skeptical about any gizmo that promises to improve your gas mileage. The EPA has tested supposed gas-saving devices — including "mixture enhancers" and fuel line magnets — and found that very few provided any fuel economy benefits. Those devices that did work provided only a slight improvement in gas mileage. In fact, some products may even damage your car's engine or cause a substantial increase in exhaust emissions. For a full list of tested products, visit www.epa.gov/otaq/consumer/reports.htm
Jamie's A/C car ran out of gas first -- Adam's windows down SUV ran for another 30 laps -- completely contradicting the computer mpg estimate. Computer estimate based on air flow into the engine, so it would appear that it is unable to properly model the difference between A/C and windows down.
10. Demand stronger fuel standards from President Obama and the EPA - The administration is considering a 47-62 mpg target after it received pressure from environmental groups, pushing for higher standards. A recent poll conducted by Consumer Federation of America also found that 62% of Americans support a standard of 60 mpg. Email your Representative, Senators, and Obama to push for a higher mpg. Currently, America is losing to the most of the world. Plus, if our cars from our manufacturers can't meet another country's standards, it can't be sold. Keeping a low standard blocks our access to major markets. The EPA would be setting the mandate and both the EPA and the National Highway Traffic Safety Administration consider the higher mileage a winner.
Plus, higher mileage, less need for oil. Keep our planet alive!