I published this a couple of years ago. It’s just as pertinent — maybe even more so — today.
It seems as though all we hear about today, at least in the “Green Community,” is fuel efficiency. We hear about the latest advances in hybrids, electric cars, ultra-efficient “city” cars, and all manner of complaints about conventional gas and diesel automobiles and trucks, and how terrible their “poor” fuel economy is for the environment.
That’s all well and good. I applaud all the efforts to recommend, encourage and produce more fuel efficient vehicles — especially since it looks as though no one is going to bother taking the issue really seriously until, to paraphrase Edward Albee, the last petroleum executive is hung with the entrails of the last energy CEO. The fact is, no one really wants to produce efficient energy until the last drop of easy profit is wrung from the petroleum, gas and bogus biofuel markets (see below).
In the meantime, we poor consumers are hung up on high fuel prices, high prices for newer, more efficient cars (with a few exceptions), and all sorts of confusing promises that are worth nothing, compared to what they’re costing us by stonewalling the real — and ultimately the only — thing that will save our butts in the long run: solar energy. (See “New Biofuel Resource Overlooks Second Law Of Thermodynamics — but what’s new?“)
Anyway, here it is folks — for free, gratis, bupkis — your chance to save money and stick it to the oil and energy cartels at the same time. It will require a little work on your part. You’ll have to learn to pay attention to what you’re doing. It will cost you a little cell-phone time. But I’ll guarantee that if you read and follow these suggestions, you’ll improve your vehicle’s fuel efficiency — and drive more safely, too.
Do I think you’ll do it? Frankly — no. Do I wish you would, for all our sakes? Oh, very much. Very, very much. For my granddaughter’s sake, as well.
Here we go…
Fuel consumption is directly related to the amount of energy used by your car. Duh! You’re thinking, “I read all that environmentalist propaganda at the top of the page for this?” It’s so obvious it’s silly, but keeping it in mind is the basis of vehicle fuel economy, regardless of what you drive. The amount of energy that you force your vehicle to use determines how much fuel you burn, and that isn’t always obvious.
What is it about any vehicle that causes it to burn energy? Weight, acceleration, and drag. Increasing weight will always increase the energy needed to move the vehicle, and increasing the other two beyond a certain point will do the same. There are some other factors, like tire pressure and braking, that we’ll get to later.
We all know that it’s harder to push heavy things than light things. What isn’t as obvious is that it also takes substantially more energy to keep heavy things moving. We don’t notice this, because when we’re driving it simply means a tiny bit more pressure on the accelerator — but it adds up. Think of pushing a car. Now think of pushing it faster. Light cars are easier to push (get better mileage) than heavy ones. Get all the garbage out of the trunk, unnecessary junk out of the back seat, and so on. Dead weight is gonna cost ya.
Imagine you’re pushing that car again. If you push it pretty hard, it will move some. Push a little harder, and it will go a bit faster, but if you want to get it moving fast in a hurry, you have to push much harder. It takes less effort to keep it moving than it does to get it moving. Same’s true when the engine’s doing the work.
Many folks have the mistaken idea that they ought to accelerate reeeeaaall slow to save gas. Not true. BMW did extensive testing back in the ’80′s that proved conclusively that moderate acceleration uses less fuel for the speed gained than either slow or fast acceleration does. Be gentle, but not totally feather-footed. In addition to giving you better mileage, it will keep you from becoming a hood ornament on some gas-guzzler’s Hummer.
When we finish accelerating, it takes energy to keep us at a steady speed. That energy is directly related to the amount of drag on the vehicle. Drag, for practical purposes, is caused by two things: wind resistance and rolling resistance.
Wind resistance is a biggie. Doubling your speed causes four times the wind resistance. (If you must know, drag is proportional to the square of the speed.) What does this mean in normal use? It takes four times the fuel to go twice as fast!
Every vehicle has a speed at which it’s most efficient, that is, it goes the most distance in an hour for the amount of fuel burned in an hour. For most, it’s between 45 and 55 mph (72-88 kph). Go slower and your mileage will decrease slowly, reaching zero miles per gallon at a standstill. This is the worst possible mileage, because you’re burning gas and going nowhere. Speed up beyond the optimum speed range, and the mileage will also drop — precipitously! At 90 mph instead of 45, you will use 4 times the fuel to go twice the distance. Not a good trade, under most circumstances.
Rolling Resistance is mostly due to tire pressure and the vehicle’s weight. Think of pushing the car again. Would it be easier with the tires flat, or with them inflated until they are hard? Obvious, right? What’s not so obvious — again, because all we’re doing is pressing the accelerator — is that the same principle applies to underinflated tires versus those with the manufacturer’s recommended pressures.
Underinflated tires can reduce your gas mileage by up to 10%. To add injury to injury, underinflation also reduces the mileage you’ll get from the tires — by as much as 70% — and here’s the kicker: with radial tires (the kind on most passenger cars) you can’t tell if they’re low by looking at them. By the time a radial is noticeably flatter than normal, it will be about 15 p.s.i. below the recommended pressure. This will destroy the tire in a fairly short time, do the same for your mileage, and may result in a high-speed tire failure that can kill you.
Check your tire pressure at least monthly, with a good tire gauge ($8.00 at an auto parts store).
Every time you touch the brakes, you waste gas! Think about it: what do brakes do? They change speed into heat. First, you burned fuel to produce heat, and your engine and transmission changed it into speed. Now, you’re taking speed that you paid good money for, and turning it back into heat, which dissipates into the air and does no one any good. A total waste.
Now obviously we can’t go around not braking just to save gas. Or can we? We’ll always have to do some braking, but we don’t have to brake as often. We can reduce the amount of braking we need to do by:
- Planning ahead. Concentrating on our driving, and keeping enough distance between us and the guy ahead that we can simply take our foot off the gas if he slows down, rather than braking. If we brake, we won’t have to brake as hard. Not only do we save energy, we probably won’t have to accelerate as much afterward, saving yet more.
- Anticipating the need to stop. If we have half a block to go to the stop sign, it’s not necessary to maintain our speed and then jam on the brakes. Take your foot off the gas and coast to the sign. If you were also watching your speed, you’ll coast up gently to the stop sign, stop gently, and save gas. (See below.) If it was a traffic signal and you’ve planned properly (allowing for other traffic) it may turn green before you get there, saving even more gas you would have needed to accelerate.
So, here are the quick rules for driving efficiently:
- Keep your vehicle tuned up and running properly. At today’s gas prices, the additional 3-8% efficiency will add up quickly.
- Keep your tires properly inflated.
- Accelerate moderately and smoothly.
- Drive no faster than you have to.
- Avoid unnecessary braking — plan ahead.
- REMEMBER: every time you take your foot off the accelerator, you’re driving for free!
My Hyundai Elantra is EPA-rated 24 city, 33 highway. That’s almost exactly what it gets in normal driving. I can, with relative ease, stretch that to 26/39 — I’ve done it. I do it routinely. That’s an average of 13% — but 18% on the road. You can have comparable savings. It’s up to you. You can even make a game of it.