How to get Better Gas Mileage Sensibly and Safely

When I wrote my "I can drive 55" hub, I mentioned that it was competing for better gas mileage that finally got my wife to slow down on the highways. Although she used to be one of those people passing everyone, jockeying for the best lane and cursing at those who were driving below the speed limit, she  now often even drives more slowly than I would and agrees that it is smarter, safe, more relaxing and saves us a lot of money.

I attributed this to the Miles Per Gallon indicator built into our 2007 Subaru (by the way, we do love our Subaru). and, of course, the high cost of gasoline. That cost has come down a bit from its record highs, but for those of us who spent most of our lives with gasoline well under $2.00 per gallon, current prices are still in uncomfortable territory. I get a queasy feeling every time I fill up and see that final figure on the credit card printout.

I get that feeling again when I get our credit card bill. We use one card exclusively for gas and the typical monthly amount does not make me happy.

We have better things to spend our our money on, thank you.

Hypermiling

Charged with competitive spirit and with Yankee thrift in my genes, I began researching how I could improve gas mileage. Frankly, some of the stuff you find out there is dangerous, impractical or of extremely limited value. I am NOT going to drive inches or even feet behind a truck at highway speeds to take advantage of draft. I'm not going to turn off my ignition and coast down hills. I'm not going to remove the roof racks from my car to reduce aerodynamic drag.

Fuel additives?

Nor am I going to consider fuel additives. Let's have just a little intelligence here: if there really was something that you could add to gasoline that would improve your mileage enough to offset the cost, don't you think that gasoline suppliers would already have it in there?

If they don't, what could the possible reasons be? Maybe if you actually did the math it would end up costing more? How about damage to your engine or damage to the environment? Could those possibly be reasons? Sheesh!

Gadgets

Falling for add-on gadgets is just as silly. None of these fuel saving gadgets work - if they did, they would already be standard equipment on cars!  If there were any after market products that actually worked, don't you think that reputable service shops would be selling them?  Wouldn't they be front page news in Consumer Reports and Time and Newsweek?

Reasonable gas saving tips

Of course there are ways to save money.  Most of them are simple and obvious.

Speed

Driving slowly saves gas. Aerodynamic losses increase with the square of the speed, so the faster you go, the more gas you burn. However, most automatic transmissions kick in a fuel saving device right around 40 mph, so your best mileage is probably at that speed or above.

That fuel saving device is called a torque converter clutch; it locks the transmission so that it is no longer using spinning transmission fluid to drive your tires. As noted, that is usually set to kick in around 40 mph.

By the way, if your car is not getting the mileage it used to, a failed torque converter clutch could be the culprit.

The calculation of maximum fuel economy gets pretty complicated, but for most cars, the "sweet spot" is between 40 and 60 MPH. Below or above that, you are not getting the best gas mileage. It's that simple, and speed is the item that will have the biggest affect on fuel economy. Slow down and save money.

Cruise Control

Many articles on gasoline mileage recommend using cruise control, but it's not always the best choice. It does help maintain a steady speed and that certainly is better than driving erratically.

However, hilly terrain with many quick ups and downs can cause cruise control to use more gas than you need to consume. If you could get up the hill with only a slight increase in pedal pressure while losing a small amount of speed, that could be better than having the cruise control maintain your set speed. Going downhill, if you are already driving slightly under the speed limit, you can let the vehicle speed up, which can give you a boost for the next uphill section. Cruise control will throttle you back and lose the momentum.

Cruise control can also interfere with keeping a good following distance.  You want a healthy distance between you and cars ahead of you both for safety and also so that you can try to avoid dropping your speed too much.  If cars ahead of you slow suddenly and you are following closely, you will have to slow to their speed.  If you have a good distance between you, you may only have to slow slightly as they resume normal speed.

Acceleration and coasting

Jack-rabbit starts from green lights and stop signs ruin fuel economy. Driving away gently and slowly really bothered my wife because she felt that the people behind her would be angry. Well, sure, there are people who expect you to race away with tires squealing - ignore them. They will get over your "stupidity" in saving gasoline.

However, if they pull up on your tail and are beeping the horn or shaking their fists at you, pull over and let them go by. Yes, they may be a rude, obnoxious jerk. On the other hand, they may have a genuine reason for needing to go faster.  You might be preventing them from getting to a loved one in a hospital or a vital meeting with our President - let them go.

When approaching a red light, coast toward it and even brake if no one is right behind you. The idea is to maintain momentum: the light may turn green before you get there and you will need less gas to get back up to speed.

Approaching a stop sign, coast if there are cars already there. You want them gone before you have to stop, because the more time you spend stopped, the more gasoline you use.

By the way, on many fuel injected cars, the fuel injectors shut off when you coast in gear, so that can be better than coasting in neutral and coasting in neutral may give you less control of the vehicle.

Unnecessary weight

Carrying sand bags is probably stupid, but so is removing things you actually may need.  I keep basic tools, a small shovel, flares and a few other "might need" things in my car.  Yes, they add some weight, but if I found myself stranded for lack of a simple screwdriver or snow shovel, I'd be pretty unhappy.  So yes, if you are hauling around a bunch of stuff you really don't need, take it out, but don't go to extremes.   I often carry a few books with me in case I run into down-time; I don't consider them "unnecessary".

Windows down or A/C?

Most everyone seems to agree that it depends on your speed; windows down is likely best at low speed, use A/C on the highway. But "low speed" of course depends on the aerodynamics of the vehicle, so the arguments about how much fuel is saved or wasted ensue. The arguments about A/C vs. windows down get very heated because of all the complicating factors.

If you have a gas mileage indicator on your car, you can test which is better for your particular vehicle by driving over the same route and testing each. Even so, whatever result you get is specific for YOUR vehicle at that speed.

Personally, I do whichever makes me most comfortable on that particular day.

Left Hand Turns

Let's say your normal route to work requires a left hand turn against traffic. How much time do you spend idling waiting for a light to change or for traffic to die down? You might be better off to change your route and make three right hand turns instead. You'd need to test that over several trips to see if it does.

When coming out of a store where you need to turn against traffic, it can sometimes make sense to go right, look for an opening where you can make a left turn into a store on the other side of the road, and then re-enter with a right turn for the direction you want to go. This can save money over idling and also can be much safer.

Ready to go?

When you get in your car, don't start it until you have buckled your seat belt, adjusted the mirror, turned on the radio and done everything else that you might otherwise do while your car is idling and not moving.

Parking Spaces

When you pull into a parking lot and it isn't inclement weather and you aren't handicapped (permanently or temporarily), park in the first space you see. Walking to the store is cheaper than driving to get a closer space. Parking far out also makes it less likely that your car wil be hit by someone else.

It also can make it easier to find a space where you will be able to drive straight out rather than having to back up first.

If you are parking on a hill, consider what your direction wants to be when leaving. If you can head downhill with one extra turn or two, that could save you gas.

Drive less

We plan our trips carefully and combine shopping with the post office and so on. Just cutting back on extra trips alone has saved us a lot of gasoline.

Cheap gas or High Test?

This is another place where the arguments get heated. The reality is that you should use the gasoline your owner's manual recommends. It is really that simple.

Worth driving out of your way to save gas?

The math is usually easy enough. Let's say your car gets 30 miles per gallon. There's a gas station 5 miles out of your way that is 5 cents a gallon cheaper than where you are right now. That's a ten mile round trip, so you will use one third of a gallon of gas. If gas is around $2.40 a gallon, that's 80 cents to get there and back. At 5 cents per gallon saved, you need to buy 16 gallons (80/5) just to break even.

Short answer: usually no, it isn't worth it.

Worth buying a more efficient vehicle?

Again, the math isn't hard. You have a 10 mile per gallon gas guzzler now, you drive 30,000 miles per year. That means you'll be buying 3,000 gallons of gas, right?

You spend a whole pile of cash to by a 50 mile per gallon hybrid. You are now going to use only 600 gallons of gas. Call it 2,400 gallons saved at $2.50 a gallon and you save (drumroll, please) $6,000.00 - it would take six to eight years to recoup the likely cost of that hybrid.

So, usually, no. You may have other reasons to buy a new car, but if you are reading this in 2010, you might want to wait a few years, as mandated fuel economy standards are set to increase sharply soon.

Gas Cards

I mentioned that we use one credit card for gasoline purchases.  That's because it's a card that pays us 5% cash back on gasoline purchases.   These types of special offers come and go all the time; when one loses  advantage, we dump that and switch to another.  A 5% kick back on a $30 fill-up is $1.50 - that adds up!

Basic Maintenance

Oil changes, tuneups, properly inflated tires, air filters - no brainers. The actual gas savings don't necessarily amount to a lot, but these are things you need to do anyway.

What about you?

Do you care about saving gasoline?  Do you have any tips I missed or want to argue passionately about something I got wrong?   Let me know in the comments.