A personal guide for improving fuel economy (8/29/05)
Given my most recent postings it must be obvious I'm a little concerned about gas prices. I drive quite a lot so it matters to me. Coming into work today I passed a gas station by the highway which always has prices 5 or 10 cents/gal. above the others, but it was still a shock to see the premium price: $2.99/gallon. With the hurricane hitting Louisiana these prices are expected to go up more, not decrease, so the topic of the most recent Economist seemed even more important: Oiloholics.
Catchy. I like it. They pointed out something I didn't know, which was that Europe's petro prices are so high because the governments tax them to discourage folks from using it too much, much like the prices of cigarettes here in the States. They also said that our take on it is just the opposite; that we'd focused on fuel efficiency instead. I can't really find fault with that. This is a country where freedom of movement is sacred so limiting that, even by making it more expensive, would surely be viewed by the public as treasonous. So fuel economy then...
When I bought my car last year I started tracking the miles driven and gallons of fuel consumed, mainly because a friend said it could show me when something was wrong. It isn't that much trouble so I've stuck with it. My average Miles per gallon (MPG) was about 35 back then, and in the past few months I've taken to learning some tricks from the hybrid folks who like to call themselves "hypermilers". The name is appropriate. I hit 44MPG one time. I've been hooked since. I average 37 - 38 MPG now.
Consider the problem from the perspective of your engine. The more it has to struggle the more gas it will consume. That's the crux of the issue, so let's look at it from there. What has amazed me the most was finding out exactly how little there is to change and why. It turns out the car manufacturers have to tune the cars even before they get to the consumers, so when we get them they are already about as good as they'll get. Low rolling resistance tires sound like a great idea, until we find out the stocks tires are already that type of tire. Even changing tire diameter can yield dubious results. Tire width even affects driving performance so shrinking it might save fuel but cause you to total your car. There are also a lot of devices which purport to increase MPG, but a check for online reviews of most of those devices yields the truth in them.
There are a lot of "basic" tips which generally include:
- Drive Sensibly - quick braking generally yields a need to quickly accelerate, which wastes fuel more than not braking in the first place. How can that be done? Leave more room between you and the vehicle in front of you. So when they brake you can just coast. Provided enough space they'll be back up to speed by the time your reach them and you'll have saved gas.
- Observe the Speed Limit - it sounds droll but my average MPG went up by 2 by dropping my average speed by 5-10 MPH. That's hundred of dollars a year. Abpve 45mph, wind resistance increases exponentially as speed increases, so the slower you drive the better your fuel economy will be.
- Remove Excess Weight - less weight for the engine to carry.
- Avoid Excessive Idling - less time the engine is running.
- Use Cruise Control - some folks say this is bad, others say good. It depends on how it behaves on your car. You don't want the car trying to stay at 70 while going up a steep hill. Instead speed should decrease so gas can be saved, but not so much as to completely back up traffic, which will just earn you a black eye. I try to stick to 2500RPMs, rather than a speed. It works, though it'll be a different value in different cars.
- Use Overdrive Gears - even automatics have an over drive button. I've no idea of why, because your supposed to leave it on all the time. Turning it off could probably help us get out of a ditch, but beyond that your going to want it on all the time.
- Keep Your Engine Properly Tuned - the mysterious world of the engine... remember what I said. By the time you get it, it is already tuned as well as it can be. Don't screw around in there and have a mechanic keep it in top condition.
- Check & Replace Air Filters Regularly - This will generally be changed with your oil change. Less air to the engine means less oxygen which means the gas can't explode as much which means it'll take more gas to get us around.
- Keep Tires Properly Inflated - over or under inflated tires screw up all that engine tuning and, regardless, will wear out quicker. Save your money.
- Use the Recommended Grade of Motor Oil - again, for the engine tuning. A heavier oil will make the engine work harder because there is less lubrication. Lighter may not lubricate enough or carry the heat away, causing damage.
- Plan your trips carefully and take fewer of them - combining trips and doing them in order of distance, rather than crisscrossing all over the city, will keep your miles driven down and save gas. Less miles on the car will also mean a higher resale value, so focus on that if you need to.
Taking this further than the tips above is like the difference between a runner and an Olympic runner. The Olympian is playing in a market were very small differences matter and add up, so you have to take care of those things and get on a program to keep them all in place. So let's have an overview:
- Conserve momentum and drive like your brakes don't work - This is the drive sensibly philosophy taken to the extreme, but it can help and it has been surprising to me of just how little it has hurt me. I don't need to brake as often so my drive is less hectic. I also find that people will get behind me because I maintain a consistent speed and can "iron out the bumps" because of that. Again, less hectic, and I actually feel like I'm doing something to end the traffic jams, which is rather nice.
- Route analysis - Traffic lights are bad, so chose a route that doesn't have them unless it'll significantly delay you. Likewise, traffic jams are bad. I talked above about reducing my speed, which seemed like a bad idea till I realized that most of my commute was spent at 40mph on the highway anyway. I get into work 10 minutes later and far less stressed, so its worth it.
- Driving analysis - your going to have to accelerate at some point, of course, so why not wait till your on a downhill to let gravity do some of the work for you? Use an onramp that'll enable this. Why not let the curve of exit ramps, an uphill slant, or taking your foot off the accelerator "brake" you rather than using brakes? Use caution, of course. Why take a hilly route when the flat one is only 5 minutes longer?
- Change the body of your vehicle - this one is dangerous territory, but the benefits are worth it. Changing the coefficient of drag (Cd) can result in some drastic savings so the easiest thing to do here is buy a car with a decent Cd in the first place. Too late? Dropping the car can help although I like not loosing the bottom of my bumper so I'm not about to do this. Adding a "sheet" of some kind to the bottom of the car can help reduce drag and would have the same effect. If possible changing the bumper design to be smaller would also help.
There are loads of tips and tricks that can help out, but the most important is exactly how much of an impact a simple change in driving habits has had on my wallet, the environment and even my health. Gas crisis? Some reports figure Americans drive over 2.5 trillion miles per year, and the average MPG is still just 21mpg. If a simple change in driving habits can change that to 23mpg, the same increase I found with myself, it could equal a savings of nearly 26 billion dollars a year if done nationally. The reduction in demand would increase supply and ease prices back down to levels even the media would have a hard time worrying about.
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