Saturday, March 15, 2008

Improving Fuel Economy

OK, you know driving isn't good for the environment, but you're going to do it anyway. Here's how to substantially increase your fuel economy without buying a new car:

1- Drive deliberately; accelerate gradually. A car uses a lot of fuel when it's accelerating rapidly.

2- Drive 55 mph on the highway. This makes a huge difference. It maximizes fuel efficiency by reducing wind resistance, which exponentially increases with speed. This reduces gas consumption by more than 20% relative to a speed of 75 mph. 60 mph is almost as good, if 55 is to slow.

3- Draft a truck. Large trucks with flat, square backs leave a massive low-pressure zone behind them, which you can exploit to save gas. At 20 feet behind a standard 18-wheeler, you will use about 27% less fuel. If that's too close, you still save 20% at 50 feet, and 11% at 100 feet. Be careful because trucks have a blind spot behind them, and some truckers do not appreciate drafting.

4- Keep your car well-maintained. Clogged filters, faulty oxygen sensors and flat tires all hurt fuel efficiency.

5- Lose the cargo. The more weight you have in your car, the more fuel is required to get it up a hill or accelerate it.

6- Turn off accessories. AC is the biggest power drain, but the fan used to circulate air also draws power.


Ross said...

All good ideas, with the exception of drafting. That sounds very dangerous! Even at 50 feet you'd only have about half a second to react if the truck suddenly stopped.

Some other ideas... keeping tires inflated (can save up to 3%). When the light ahead is red, take your foot off the gas pedal and coast.

I heard this on the radio, on a story about some guy who gets like 100mpg out of a ford pickup truck through obsessive driving. When parking in a parking lot, coast to the highest elevation spot you can find before you stop and turn off your car. Later when you are leaving the lot, use the downhill drop to give yourself enough speed to leave without having to use much gas.

Stephan Guyenet said...

One car length for every 10 mph is the general rule, so if you're going 60, that's 6 car lengths or 80 feet for my Civic.

So yeah, 50 feet is a bit close "by the book" but in practice people are often closer than that on the highway, even if they're not trying to draft.

Stephan Guyenet said...

By the way, I like the idea of parking on an elevated spot, that's hilarious.

Ross said...

Yeah the story was really funny, I wish I could find it. The guy sounded half genius half insane.

Another more practical tip is only filling up your gas tank partway when refueling. An extra 6 gallons of gas on hand just increases weight and reduces fuel efficiency. (But increases convenience). I guess you gotta weight the trade-off of more trips to the gas station - which themselves use fuel. And consolidate small errands into one big shopping run. When your engine is cold it is least fuel efficient. If you keep driving and stopping repeatedly, your engine will stay warm and you'll get more miles per gallon than if you had done each errand on a different day.

Anonymous said...

Um, stay out of Seattle? I was once driving a rented Daewoo in Seattle, and when I took my foot off the gas going up one of those steep, steep hills, the car stopped. Completely. As if I'd braked.

Then again, I'm sure I got phenomenal mileage on the way down. So maybe it's a wash.

Using your pedals gently (coasting to a stop when it's safe to do so and accelerating slowly rather than braking and accelerating hard) are the two best hints. I'm glad you mention them; I don't think most people think about them.

Also, please tell the 55 mph crowd to stay in the right lane. It is a traffic hazard to be in the middle, or >gasp< left lane.

Jackie Patti said...

I used to be a trucker, and as such there is little I hate as much as tailgating.

If you are distracted even momentarily, you will not hit my trailer. You will drive under it and be decapitated.

If you make me tailgate, by passing and pulling in front of me without leaving sufficient space, again, I am at no risk except for how bad I will feel for killing you.

I've discussed with many truckers, and they agree my metaphor is accurate, that being a trucker is like being the only day care worker in a room of electric outlets and a hundred kids, all carrying forks.

If you want to kill yourself, go right ahead, that will certainly save you fuel since you'll never have to buy any again.