1. Does filling up in the morning really save gas?
Absolutely! Gasoline expands and contracts with temperature changes. A tank can show 20 gallons of gasoline in the morning, have some gasoline taken out, and yet still show the same level of gasoline in the afternoon! Here's the thing; gas is sold by volume, so one gallon of cold gas will give the mileage of perhaps 1.1 gallons of warm gas (by way of example), but you're paying for just one gallon! Leave the house a little early and fill your tank up in the early morning when it's the coolest. And, of course, look for the lowest prices at REPUTABLE filling stations. A clean exterior usually means clean gasoline.
2. Does topping off the tank more often when prices are going up save gas and money?
What it does is save money ON gas. This may be hard to understand, but here goes: When evaluating any inventory that you are depleting, you want to take into account the cost of replacing that inventory. Suppose you use a gallon a day, you have a 22 gallon tank, and prices go up an average of one cent a day. Hopefully you're never letting the tank get lower than the last two gallons, so you go twenty gallons between refills. If you wait the full twenty days to fill up, you will spend 20 cents more per gallon, equaling an extra $4.00. But, if you'd been topping off each day, instead of 20 cents more for each gallon you will have paid one cent extra the first day, 2 cents extra the second day, etc., until at the end of the same twenty-day period you find that you've spent only $2.10 extra FOR THE SAME AMOUNT OF GAS! That may not sound like much, but multiply that out for the year and it adds up. Furthermore, ask yourself this: If you were told by a gas station attendant that the pumps on the left would give you the same amount of gas but would cost you almost $2.00 less per fill-up than using the pumps on the right, which pumps would you use? Of course, the opposite holds true when prices are going down. In that case, which is all too rare, you would save money by waiting until you're nearly empty because each day that passes yields greater savings in cost per gallon.
3. Does proper tire inflation really save gas?
Not only does proper tire inflation save money on gas, but it can also save your life. Improper inflation is a leading cause of tire failure, but we're not talking about getting a flat tire - we're talking about catastrophic tire failure, where the tire explodes, disintegrates, or plain comes off of the rim while you're driving. Remember the Firestone/Ford debacle? Firestone's claim was that Ford was not using the originally recommended tire pressure, causing some serious accidents. That said, underinflated tires put more rubber on the pavement, increasing road friction, AND hindering the tire's ability to dissipate the heat from road friction, which causes a vicious cycle of creating even more friction and heat. The friction will hurt your fuel economy and the heat will hurt your tires - which in turn may hurt you if the tire fails.
4. I understand a dirty air filter hurting fuel economy, but doesn't a dirty fuel filter make your car use LESS gas?
Lessening the amount of gas to increase fuel economy may make sense intuitively, but that's not how to save gas and money! Keep in mind that intuition tells us that heavier objects fall faster than lighter ones, and Galileo proved that wrong hundreds of years ago. What actually happens is that a clogged fuel filter causes a leaner fuel mixture. That will make the combustion of the air-fuel mixture LESS efficient as it gets worse. Why? Without getting too much into chemistry, the fact is that gasoline burns best at the correct ratio of air to gasoline (14.7 pounds of air to each pound of gasoline). Not enough air causes inefficiency as does too much air. One of the clues a mechanic picks up on a car with too lean a fuel mixture is a high hydrocarbon and high oxygen reading of the exhaust fumes. Hydrocarbons are unburned gasoline resulting from the misfire caused, in this case, by not enough gasoline in ratio to the oxygen. In plain English, the engine now has to work harder to give the same amount of power. That always hurts fuel economy.
5. Can I save gas by opening the windows instead of running the air conditioner?
Sort of, maybe, but actually no. Assuming you're travelling at highway speeds, recent studies have shown that modern cars, with much more efficient air conditioners than their predecessors had, actually show very little, if any, difference in fuel economy between running the A/C and having the windows open - both shave off about 2% to 3%, assuming everything is in proper working order. This was NOT true for trucks, SUV's and other larger vehicles. Larger vehicles got WORSE fuel economy in these tests with the windows open than with the A/C on, likely because of the much greater interior volume acting almost like a parachute with such vehicles. Of course, you save the most gas and money by driving with the windows closed and the A/C off, but that's not always possible.
6. Should I leave the car on if I'll be idling less than three minutes since it takes even more gas to start the car?
Not anymore. Actually, that three minute figure was a rough approximation, at best. In any case, modern cars - many going back to the early 1980's and late 1970's - have computer-controlled fuel injection, making the amount of fuel required to restart a warm engine equal to as little as 30 seconds of idling. Clearly, letting the car idle for even as little as three minutes is not how to save gas and money. If you know it's going to be a few minutes and you're not in traffic you'd do better to shut the engine off. Additionally, modern cars don't need a warm-up period of more than about thirty seconds when cold starting - unless you're in extreme cold where you probably want to get a block warmer.
7. I keep seeing mechanical gadgets that are supposed to save money on gas. Do they work?
I've seen all kinds of gizmos and I'm sorry to say that, while many of them make sense on paper, most of them don't seem to work. I also have to admit that a lot of the problem is that people were trying to find a way around fixing important mechanical failures. Always keep your vehicle in good repair (one of the best ways to save gas and money in the long run) -- attaching some additional device to an engine with weak compression or some other defect is not likely to deliver favorable results. It's like trying to use a squirt gun to put out a major forest fire. As for cars that ARE in good repair, some things may work, but if your car is under warranty you need to be careful that the gadget does not void the warranty. Right now I'm following the "hydrogen from water" concept, where the car's electricity is used to separate water into hydrogen and oxygen, which is then drawn into the air intake. I've seen some impressive demos of them even being used by government agencies. I'm looking to install one myself.
8. Do additives save gas?
That's a broad subject. The broad answer is yes - depending upon the situation (please avoid fighting forest fires with squirt guns!). Brand-name additives for cleaning fuel injectors are generally effective in that dirty injectors and valves most definitely will hurt fuel economy. As a matter of fact, on older cars I was often able to save my customers a lot of money on carburetor overhauls by running a very high concentration of injector cleaner through the system. Obviously this was not for carburetors that had mechanical, "hard parts" failures. With newer cars you need to be careful and, with just about any car from the 1980's on up, make sure that any product that will pass through the intake and exhaust system is sensor safe! Also, rather than use premium gas on a car that doesn't call for it, I recommend using regular gas and pouring a bottle of injector cleaner in with a fill-up every two months or so, depending upon how much driving you do.
9. What about oil additives?
That's a highly conditional "Yes". There is the old stand-by, Marvel Mystery Oil, which many mechanics will tell you is really transmission fluid. Marvel Mystery Oil does two basic things: First, when added to your gasoline it burns off carbon build-up in the combustion chamber, thereby reducing pre-ignition. If you do this and see smoke coming from your tailpipe you either used too much or you most definitely DID have carbon buildup, meaning the temporary smoke caused by burned-off carbon was a good thing! Before detergent motor oils came along you used to have to "de-coke" your engine on a regular basis - same basic thing. Second, when added to your oil it provides an extra bit of cushioning and lubrication for your valves and valve stems. In either case, these situations should not be an issue on newer cars. STP Oil Treatment is good in that it is a viscosity index improver. Do NOT disregard the directions on the label as it will end up being similar to using too high of a viscosity motor oil. STP also helps reduce engine wear by leaving a protective film for when you start the engine, when most engine wear takes place since normally there isn't as much oil pressure at that time.
10. Do those oil additives with PTFE help save gas?
Yes, but according to study after study, only while it or its residue is present in the engine. PTFE undoubtedly does reduce friction. What is in doubt is the ability to get it to actually bond to engine parts. It takes extremely high temperatures to get PTFE to bond to metal - temperatures you don't get except perhaps in the combustion chamber itself, thereby excluding all of the bearings, the cam shaft(s), rocker arms, valve stems, lifters... well, you get the picture. But while the additive is still in your engine it DOES provide better protection. It's expensive to add that to every oil change, but for a collectible car you may want to go with it, though saving gas doesn't usually go hand-in-hand with driving a collectible.
11. The owner's manual says I only have to change the oil every 7,500 miles. Is my mechanic trying to pull one over on me when he recommends every 3,000 miles, or will I get better gas mileage this way?
You will get better gas mileage - especially in the long run. Frequent oil changes will help prevent engine wear and sludge, both of which will kill engine efficiency as they get worse. As for the discrepancy in recommended oil change intervals, they're both correct. How so? If you read the owner's manual carefully, as in the fine print, you'll find something to the effect that for hard or heavy duty you should use the shorter interval. Here's the issue: what constitutes heavy duty? Heat, cold, dust, humidity, stop and go traffic... I don't know about you, but I can't think of ANY place that doesn't have any of those conditions! So why do they print that in the manual? They want to be able to report a low cost of operation while giving you a realistic guideline. Go with 3,000 miles unless you're using synthetic oil. And, yes, synthetic is better and I would strongly suggest you continue using it in cars that call for it in the owner's manual. And use the manufacturer's recommended viscosity of oil. That, too, can make a difference in fuel economy and warranty coverage.
12. Do driving habits really save gas?
Well, yes -- if they're good ones! This is exactly why I get around eight more miles per gallon of gas than my wife does with the same car! Taking off from a red light gradually, not too slowly, but not jack-rabbit starting, makes a TREMENDOUS difference in the amount of energy used. Moreover, you always want to be in the highest gear at any given speed that is safe for the given road and traffic conditions. At 45 miles per hour on level ground I will be using fifth gear while my wife will be in third, MAYBE fourth, gear. I don't blame her - she's used to driving an ambulance, where the priority is saving lives, not gasoline. You don't drive a stick shift? Well, this still applies to you in the sense that most automatic transmission drivers don't realize that very often the car will not shift into the next highest gear because they're giving the engine just a slight bit more gas than needed. Once you've reached your desired speed lightly lift your gas pedal just a bit and you'll often feel the car shift into the higher gear, thereby using less gasoline to travel at the same speed. This is especially true at around 38-45 miles per hour, depending upon the transmission and driving conditions. Also remember this little rule: Every time you are pressing the brake you are wasting the gas that you used to get up to that speed. Obviously, that's not always true, but it does increase your awareness of driving too fast (you can virtually always lower your speed to save gas so long as you drive safely and above the MINIMUM speed limit). Look ahead so that you can just let up on the gas pedal, rather than having to go hard on the brakes. You also may want to take a look in your trunk to make sure you're not carrying around useless extra weight. I helped one man save a lot of money on gas by pointing out that when test-driving his car it felt like something very heavy was in the trunk. His jaw dropped as he remembered that his deceased mother's china was in there - inside a cedar chest! No word on whether anything got broken...
My intention in writing this article was to provide techniques to save gas and money and also give the reader an insight into why these techniques work. These are probably the most important pointers on saving gas that I, my friends, and my customers put into use. Drive safely and wisely!
