Smart SpendingSmart Spending

Fact or fiction? 8 gas-saving myths

Let's examine some commonly held beliefs about how to get the best gas mileage from your vehicle.

By MSN Money Partner Apr 15, 2011 4:32PM

This guest post comes from Lou Carlozo, Green Dad columnist for


The Kelley Blue Book folks have just named their top 10 green cars for the 2011 calendar year, a seeming boon for drivers seeking eco-friendly automotive alternatives. But if you're anything like me, you might think it's not easy being green, especially when the path to environmental friendliness runs straight through your wallet like a Hummer on steroids.


A bare-bones 2012 Ford Focus -- No. 10 on the Kelley list — runs $16,270. And that's cheap compared with the fourth-ranked Lexus CT 200h, weighing in at $29,120, also without options. Ugh. To add insult to injury, any new car depreciates the second you drive it off the lot. Post continues after video.

So for those of us who don't have five figures to spend on a gleaming set of wheels, take heart: The greenest car may well be the one you already have, provided you take steps to make it more fuel-efficient and environmentally sound. This is especially so because you're going to need those five figures to pay for skyrocketing gasoline this summer (you can also follow my tips on ways to save money on gas).

This week, Green Dad sorts the fiction and fact when it comes to making your machine run in harmony with the planet.


Fact: Driving slower saves you gas. Like millions of Americans, I listen to the "Car Talk" guys on National Public Radio mostly because they make me laugh. But they also dispense great auto advice, and they stress that slowing down makes a big difference: For every 1,000 miles you drive (figuring gas at $2.50 a gallon and 25 mpg fuel efficiency), you'll save as much as $15 driving 10 mph slower. Of course, if gas is nearly double that price,  the savings should double as well. Something to think about if you're a speed demon.


Fiction: Replacing the air filter on your car improves mileage. Every time I go for a quickie oil change, the tech comes out with an air filter that looks like dirt, which shames me into coughing up to replace it. But if your motivation is better gas mileage, consider skipping the change. The U.S. Department of Energy reports that an air filter change will mostly help your acceleration, not your mileage -- though if you drive an older car with a carbureted engine, it may improve fuel economy 2% to 6%.


Fact: Stepping on the brakes wastes gas. This one also comes courtesy of Click and Clack on "Car Talk." "Every time you use the brakes, you're wasting the 'acceleration' you've already used. Instead of moving your car, that energy is being transformed into steaming hot brake pads," they say. Instead, learn to anticipate stops, and gently accelerate your car from a standing stop. For more of those great "Car Talk" tips, click here.


Fiction: Gas-saving additives can improve fuel economy by 20% or more. What's the difference between motor oil and snake oil? Not much, if you're weighing the claims of slick entrepreneurs who know the timing's right for selling you magical gas-saving potions. To be sure, some long-standing products with modest claims (such as STP Gas Treatment) have vigorous supporters, but they only claim to boost mileage about 10%.


But as the Federal Trade Commission warns, "The Environmental Protection Agency has evaluated or tested more than 100 alleged gas-saving devices and has not found any product that significantly improves gas mileage. In fact, some 'gas-saving' products may damage a car's engine or cause substantial increases in exhaust emissions."


Fiction: New "low-resistance" tires significantly improve gas mileage. Unless you're driving bald or severely underinflated tires, the hype about low-rolling resistance tires adds up to minimal gas savings. As this story by USA Today reports, various brands of these newfangled tires create gas savings of only 1% to 3%, even if rolling resistance is cut by 25% or more. Whether that saves wear and tear on your car is another story, but the mileage improvements won't even pay for a spare tire over the course of 10 tanks of gas.

Fact: You can realize dramatic mileage improvement by replacing your oxygen sensor. This falls under the category of tuning up your car, always a good idea if you want to see gas mileage gains in the 4% range. As a function of any proper tuneup, ask your mechanic to look at the oxygen sensor; if it's not working properly, a simple repair to this part (commonly costing between $50 and $120) could boost your mileage by as much as 40%, the U.S. Department of Energy states.


Note that if you make this fix, it may take a few weeks for you to realize the improved mileage as your engine's fuel-air ratio adjusts.


Fiction: Topping off the gas tank is a good idea. I know, I know: You've finally found the one pump between here and Logansport, Ind., that has affordable gas, so why not squeeze every last drop into your tank? While that sounds sensible at first blush, here's the problem: Gas expands in warmer weather, which means topped off gas will likely wind up spilling out your tank.


As if you needed more incentive, check out this warning from the U.S. Environmental Protection Agency: "Topping off the gas tank can result in your paying for gasoline that is fed back into the station's tanks because your gas tank is full." So unless you’re in the mood to pay the folks at Exxon or BP a little more for your fuel, stop topping off your tank.

Fiction: High-octane gasoline improves your mileage. I'm amazed to see that countless drivers still fall for this marketing gimmick, despite abundant evidence that high-octane gas is a waste of money. Props to the folks at for pointing this out, along with other gas-saving tips you can read here. Bottom line: Unless your car specifically requires premium, skip it and go for low-octane fuel.


More on and MSN Money:

Apr 15, 2011 9:25PM
Changing the air filter when it's dirty may not save gas, but it'll sure save an early engine overhaul!
Apr 16, 2011 12:41PM
Come on people!  FORGET about the  ""clean" air filter, the oxygen sensor, or the OZONE layer..!  One guy hit it.  Its ALL in the way you PRESS on the gas and brake pedals...LOOK ahead at Green/Red lights and slow down to time your arrival to the light when it is green.  LIghten up on your braking/acceleration. Racing off the line at the green light is for the Indianapolis 500...not at the corner of Indian Way and Main Street, Anytown, America!!!  I dont need to "measure" my mileage at all.  Driving according to this method, of NOT RACING from one Red light to the next, gives me the Best mileage possible, saves on Brake wear and keeps my Blood Pressure @ 100/60!
Apr 16, 2011 7:06AM

Let me add my 2 cents here.  I tried the 0% ethanol gas in my SUV and I had gotten better gas mileage and my vehicle performed so much better.


I did the mileage on it after using it for a bit and I had gotten 363 miles out of a full tank of gas before my light came on, usually I only get 326.  It did cost me $68 to fill it up at 3.82 or 3.62 a gallon but it lasted me alot longer than if I had used the cheap stuff.  I also put in $10 of the 89 octane yesterday but it didn't last long at all, it was like I was using the cheap stuff.   I had gotten just a hair under a quarter of a tank of gas and my car did not run as well. 

Right now that gas cost $3.99 a gallon and I will be happy to hand over the money.

I feel like I am getting my money's worth using the 0% ethanol gas.  there was only one gas station here that I knew of that sold it.  Now there are two.  Hopefully it will be making a comeback.  If any of you see that sold in your area I would say go for it and don't even think about the extra money that you are paying at the pump.  It is well worth it.


This lady is happy going along with the 0%, my car seems to love it too.  I am all for helping out the eco system but I don't think it is worth it having the ethanol in the vehicle.  Now if my car was made for only that then sure I would use it but since it is not and not even a flex vehicle I am not worried about it.  My dream car is an all electric car to scoot around town in. Someday, someday. 

Apr 16, 2011 9:11AM

Hi BillWP!  You wrote:  "Its a common belief that if a truck owner lowers his tailgate,,it will save on gas because it reduces wind resistance. I have yet to see anything to confirm or debunk this"


Actually, "Mythbusters" did. It's a myth.  There is a wave of air that passes rolls over an empty bed and it reduces drag with the tailgate closed compared with the tailgate open.  Detroit designers have done this type of study for decades to incorporate a drag component to trucks.

  The effect is similar to how the Kammback design works. 


  If you fill the bed, though a lot of things change for the flow...including putting on a camper.  A tonneau cover works well too and doesn't hurt drag from what I've seen.

  Keeping the gate closed is common knowledge up here in the Toledo-Detroit area because of the worker's commitment and proximity to auto technology. It's funny, union workers save billions in losses by  companies sometimes fixing bad designs and repairing weird management ideas and production methods with suggestions and study groups. Auto factory workers are some of the most interesting professionals in the world.  If you think this is a plug, it is. They put up with stuff and make stuff in ways you wouldn't believe.  They make it look so easy, by being pros, that you'd THINK it was easy!    I hope this helps!


Apr 15, 2011 8:23PM
Replace air filters. Keep a close eye on your engine's air filter. When the engine air filter clogs with dirt, dust and bugs, it causes your engine to work harder and your car becomes less fuel-efficient. Replacing a clogged air filter could improve your gas mileage by as much as 10 percent and save you 15 cents a gallon. It's a good idea to have your engine air filter checked at each oil change. The Car Care Council recommends changing your car's air and oil filters every three months or 3,000 miles or as specified in your owner's manual. This is bank rate and here is msn:

Fiction: Replacing the air filter on your car improves mileage. Every time I go for a quickie oil change, the tech comes out with an air filter that looks like dirt, which shames me into coughing up to replace it. But if your motivation is better gas mileage, consider skipping the change. Us dept. of energy reports that an air filter change will mostly help your acceleration, not your mileage -- though if you drive an older car with a , carburetor engine it may improve fuel economy 2% to 6%. What gives don't believe anyone
Apr 16, 2011 2:08AM

The author is contradicted, the air filter only adds to acceleration and yet the brakes waste gas because you lose "acceleration". The air filter does save gas, I use the K&N air filter, with a 1,000,000 mile warranty it does pay for it's self. The KEY to good gas milage IS NOT any 1 thing, it is a number of things.


PROPER TIRE INFLATION: It will save a bunch on gas, the info for that can be found on the tire or on the sticker on the driver side door.


Do NOT TOP OFF FUEL: On newer autos it can saturate & damage valuable emissions componets.


READ OWNERS MANUAL: Some cars do take higher octane, follow the owners manual on schedueled maintenance and OIL. Most manual say in hotter temps use 5W 30 instead of 10w 30.


CHECK FLUIDS WEEKLY: Although it will not save on gas, it could save money on repairs and thats money you could put in the tank!


On manual transmissions: Higher gears will save money, the higher the engine revs the more gas it uses. use cruise control in automatics


Learn auto mechanics: Doing maintenance yourself will not save gas, but save you money you could put in the tank (there are some educational youtube vids on automechanics).


Visually inspect VACUUM LINES: vacuum lines run alot of emissions componets even a pin hole can cost fuel economy. Look for vacuum lines that are corroded and REPLACE.


There are alot more gas saving tips try checking your local DMV there could be a little pamphlet on fuel saving tips.


Apr 16, 2011 2:21PM

A couple of points to address things I see coming up in the comments over and over...


1)  Ethanol has less energy than an equivalent amount of gasoline.  You get energy from fuel from the breaking and restructuring of atomic bonds.  High energy bonds - low energy bonds = energy to get you down the road.  Less energy per unit fuel means you need more of it to do the same work, so it naturally follows that your fuel economy will drop running ethanol fuel.  Of course, they don't tell you this up front, but if your car if your car is designated "Flex-Fuel" or such, check fueleconomy dot gov to see what the difference is likely to be.  Both figures should be there.


2)  Changing your air filter is NOT a bad idea.  Granted, if it is only slightly dirty, you may not see enough difference to offset the cost, especially with the cost of filters on the newer cars.  But!  Again, it comes back to work.  Air is drawn into the engine by the downward travel of the engine's pistons on the intake stroke.  The more blockage there is in the air's path, the more energy it takes to draw in the air.  The more energy you give up working to suck in air, the more you have to put back to keep going.  Everything you can do to reduce the work the engine has to do, the less fuel you need.


And yes, as many have pointed out, all these little things get blown out the window (or the tailpipe) when you romp on it because you have to be the first to the next red light.  Your right foot is still the best means of controling fuel economy.

Apr 16, 2011 10:45AM
Fact: Driving slower saves you gas.
They don't say exactly what slower is, but I track the fuel mileage on all my vehicles. I have seen the best fuel mileage vary from below 50 mph to 76 mph depending on the vehicle.
Not all vehicles are created equal.
Apr 16, 2011 12:57AM

I'm another Car Talk Fan, listen to "Click & Clack" weekly.


But I have to disagree with your gas saving advise, or who ever advise it is. The trouble is I keep seeing the same erroneous advise.


A clean air filter is key to good mileage, carbureted or injected. Not to mention better for your engine. What you going to take the money you save by not cleaning/replacing your air filter, and replace your engine.


Tires are another thing. Keep them properly inflated! Better MPG, and saves your tires from wearing out prematurely. Tires ain't cheap, make them last.


Regular vehicle maintenance!  Take care of your car, and your car will take care of you. Not to mention last you many years. Unless you want to fork out 20-30 grand for a new one every few years.

Apr 17, 2011 11:21PM
anybody that doesn't believe driving slower saves gas is a complete fool. Air resistance is proportional to your speed SQUARED! Thus, at 70 mph, your air resistance is approximately twice your air resistance at 50 mph (70 squared is 4900, 50 squared is 2500). I LMFAO at people who think if you get to your destination faster you burn less gas! ha, its just basic physics people! 
Apr 16, 2011 12:32AM
Already knew Wal Mart was a dollar store. I hope I'm alive when the people screw the oil companies. And we will! Geothermal for your house, solar, wind. I just hope it's AMERICANS who make the the product. 
Apr 16, 2011 12:08PM
just did a comparison test in my 94 yj, got 13.9 mpg with a tank of 87octane with ethanol,then ran it empty, filled with nonethanol 87 octane and got  16.3 mpg, even at 20 cents more a gallon would realize a 41 dollar savings on a thousand mile trip, not to mention i also own a 99 tahoe and in the last 6 months had to replace muffler,then both catalytic converters, then the motor, and 3 oxygen sensors,all of which i attribute to my wifes short commute combined with ethanol gas,dont believe for a minute that this ethanol 10 -15 percent gas makes any sense, government snake oil for sure, going to cost us all in the long run.
Apr 16, 2011 1:48PM

All this talk about how high the price of gas has soared is mostly - talk. Why? Not many drivers in this country really care how many miles they get to the gallon when they are on the road. Ask how many really know the gas mileage their vehicles give them and you will see what I mean. Then, observe while you are out on the freeway, just how many do drive like they want to make a gallon of gas go the distance.

I daresay the price of gas is really not a big deal to the majority of Americans. They love to drive - fast. And they do so because it is the macho thing to do. And they will pay for the "kick" they get out of going zooom too.

Still, it is shame that we have become so conditioned to paying whatever Big Oil says to pay!

What galls me, though is that our leaders do not seem to want to do anything about how hard we are being squeezed by them. I am sure they have ways to stabilize the price at the pump. But it looks like they are sold on the idea that we should be coughing up the big money to pay to drive like the rest of Europe. But do they know that our friends across the Atlantic do not have to depend so much on the auto to get about? They have excellent public transportation systems that they can use to go just about anyplace. And many can hop on their bikes to get to where they want to go too.

So, it looks like it will be $5.00 per gallon by summer for sure!  To be honest, I dread what will happen to our economy when that happens! Like many, I will have to cut back on lots of things. Being that I am on the road, working all day, I make my usual stops for breakfast and lunch. Looks like I may have to be brown-bagging starting next week! I may have to even give up on the accounts that are way off the beaten path.



Apr 16, 2011 8:10AM
Here is a "Fact or Fiction" myth  I would have liked to have seen in this article. Its a common belief that if a truck owner lowers his tailgate,,it will save on gas because it reduces wind resistance. I have yet to see anything to confirm or debunk this. But as a truck owner myself,I tried this and haven't seen any difference either way. Does anyone have any thoughts on this?
Apr 16, 2011 1:11PM

No mileage effect, but this is the worst idea for saving money -- DON'T FILL YOUR TANK ON APRIL 15TH!  Instead fill up on the 14th or wait until the 16th.  That will cost the oil companies $3 billion and force them to lower prices by 30 cents per gallon!


So instead we give them an additional $1.5 billion a day early plus another extra $1.5 billion a day later!  Duh?  Who thought this one up?

May 18, 2011 2:55PM

There are some good tips in here. First, don't top off the tank. Even if the pump doesn't have vapor recovery most vehicles are equipped with overflow plumbing for fuel systems so the overflow from the gas tank goes to the canister and expelled...mostly as vapor. Gas not being burned in your engine is wasted fuel and money!


Don't waste money on octane your car doesn't need. It is of no advantage and is a waste to a car that doesn't need it. The lower the octane the more flammable the gas. If the octane is too low, the heat from compression will be enough to ignite the fuel before the piston reaches the top. This can damage the engine if left unchecked. If the octane is right the fuel will burn on time when the spark plug lights it up. If the octane is too high it makes no difference because the fuel will ignite on time anyway and it is of no advantage to have the fuel less flammable than what it takes to make sure the fuel doesn't light up before the spark plug lights it up.


The oil companies aren't "making up" for anything. They make about 9 cents on the dollar in profit for the oil. Uncle Sam is making 41 cents on the dollar via taxes. So who's really making all the money on oil? Diesel fuel isn't higher because the oil companies are charging more for it. Diesel fuel is higher because the taxes are higher on the fuel. Under President Clinton's watch, taxes on Diesel were increased by 50 cents per gallon. So, compare that price to unleaded and then subtract the fifty cents and see where Diesel prices would actually be if it were taxed less. Diesel has more energy per unit and is cheaper to make than unleaded so it would normally be cheaper than unleaded if it weren't such a tasty tax-magnet.


The oil companies have their faults in our situation but the government cannot excuse itself from its part either. It just keeps repeating the old half-truths about it being "the oil companies' fault" while it excuses itself from any responsibility at all and laughs all the way to the bank. Faulty government policy has as much or more to do with our energy problems as the companies that supply that energy.

Apr 16, 2011 9:56PM
It is all about engineering and maintaining according to the manufacturer along with good driving habits.  Typically the type of vehicle, i.e. within each class (truck, compact, full size, etc..) determines its basic mileage range.   My truck is designed for towing and consequently gets about the same mileage no matter what I do.
Apr 16, 2011 2:24PM
We have high gasoline prices because of unrest in the middle east! Obama bombing the middle east will cause prices to continue going up! Obama raising tax and soaking the rich is only going to cause more inflation and put more on unemployment! When you go to buy gasoline don't curse them,-- CURSE OBAMA! Obama the new Jimmy Carter! We have high gasoline prices in the United States because we have no leadership! Obama is doing nothing but tripling the National Debt!  
Apr 16, 2011 1:31PM
Apr 15, 2011 10:16PM

Your post was blocked because it has a hyperlink or appears similar to spam. Please revise your post and try again.

Please help us to maintain a healthy and vibrant community by reporting any illegal or inappropriate behavior. If you believe a message violates theCode of Conductplease use this form to notify the moderators. They will investigate your report and take appropriate action. If necessary, they report all illegal activity to the proper authorities.
100 character limit
Are you sure you want to delete this comment?


Copyright © 2014 Microsoft. All rights reserved.

Fundamental company data and historical chart data provided by Morningstar Inc. Real-time index quotes and delayed quotes supplied by Morningstar Inc. Quotes delayed by up to 15 minutes, except where indicated otherwise. Fund summary, fund performance and dividend data provided by Morningstar Inc. Analyst recommendations provided by Zacks Investment Research. StockScouter data provided by Verus Analytics. IPO data provided by Hoover's Inc. Index membership data provided by Morningstar Inc.


Smart Spending brings you the best money-saving tips from MSN Money and the rest of the Web. Join the conversation on Facebook and follow us on Twitter.