20 ways to get better gas mileage

Deleted. Y'all are right. There are way too many errors in there and I didn't pay nearly enough attention to ferreting them out before I decided to post. My bad.

As penance, I offer you this image of a Scutigera coleoptrata being eaten by a Venus fly trap. It's no unicorn, but it does a good job of summing up my failure nicely.



Image comes from Plant Systematics Resources site of San Diego State University.


  1. “Fill up before sunrise” Sorry, doesn’t matter. One of the signs on the pump reads: volume compensated for temperature. This means its pumps the same amount for a given temperature. It is pumping by density.

    1. While I fully agree with your post, it’s worth mentioning that the temperature of the ground, where the tank is buried, does not change much from day to day making compensation mostly unnecessary, except by weights and measures standards. Seasonally and locationally, there is a difference, but a car, and even a truck, won’t notice a significant difference.

      Aircraft, on the other hand, can be affected by this. That’s why large aircraft fill up with a certain weight/mass of fuel. Small airplanes still use liters and gallons though.

  2. The ‘fill up early in the a.m.’ notion has actually been tackled by Snopes.com It works, but not so well you should go out of your way for it (savings if you ALWAYS fill your car at the coldest is only about $31 per year)

  3. While it may be good for your mileage, filling up early in the day is the worst thing that you can do for the air, particularly during the summer. The fugitive emissions that escape while you are filling your tank – the vapors that get around most types of plastic shields and other methods for minimizing fugitive emissions – those vapors will collect during the day and cook into smog – ground level ozone.

    Also, keep in mind that gasoline is usually stored in underground tanks. So, I’m not sure how much difference there is in the temperature of the gasoline whether it is pumped in the early morning or mid-afternoon.

  4. Letting go of the gas well before you have to stop also reduces consumption. Most people tend to maintain their speed and apply the brakes at the last moment. What a waste of energy.
    I thought shutting down anything that drains the battery (radio, air conditioner etc.) also helped fuel economy?

  5. Man, this is one of the worst written articles I’ve seen in a while. Of course, the “save money” tips have nothing to do with gas mileage… But

    “Dirty air filters will disconnect the engine’s air supply”

    It’s a known fact that excess weight in your car caused the engine to work even harder. Being that said, having too much junk in the trunk […] can significantly affect the way your car utilizes gas”

    Wow. And w/ shawnhorey @2 debunking the temperature thing… Makes me wonder if there’s anything in this entire long article beyond “Carpool, make fewer trips, maintain your car, and don’t drive like a maniac.”

  6. At first I was going to click, but the site’s URL dissuaded me:



  7. Filling up before sunrise: Shawnhcorey points out that modern pumps adjust volume for temperature. It’s also particularly relevant that the bulk fuel is almost always stored in underground tanks, where the temperature remains constant throughout the 24 hours. The only time the pump might get warmer fuel might be shortly after a summer, daytime, bulk-fuel tanker delivery.

  8. That old “fill up at the coldest part of the day” chestnut irks me.

    Generally, fuel at filling stations is kept in very large underground tanks.

    How much / how fast does anyone suppose the temperature of fuel in a 10K gallon tank under several feet of concrete and earth will change when the sun comes up?

    My guess is the temperature barely changes all day. It probably doesn’t change a whole lot even with the changing seasons.

  9. Get a standard transmission – when I coast I shift into neutral to get the RPMs down as fast as I can, I accelerate slowly and then shift into 5th from second most of the time to keep the revs down unless someone is on my tail.

    I figure out my fuel economy EVERY fill. With almost COMPLETE city stop-and-go driving ( rarely go on the freeway) I’m coaxing 35-36 MPG with my ACURA…

    1. “Get a standard transmission – when I coast I shift into neutral to get the RPMs down as fast as I can,”

      Which uses more fuel than staying in gear, because when the engine is disengaged from the wheels it has to burn fuel to keep running, when engaged the turning of the wheels keeps the engine running requiring almost zero fuel.

      Manual transmissions save fuel in other ways.

      As for electrical stuff in the car, radios use negligable fuel. The other stuff depends on how underpowered your engine is for the load you’re putting on it.

      1. Yeah, but keeping the gears engaged keeps the RPMs up and burns more fuel than having the car running at 900 RPM coming up to a light.

  10. They forgot the biggest one…Don’t live 50 miles from where you work!

    I am amazed at the number of people who spend four hours a day in a car so they work in the city and live in some leafy suburb.

  11. @BdgBill The real curse of the suburbs isn’t the pull to buy a nicer/fancier house 50 miles from your workplace – it’s that the only house you can AFFORD is 50 miles from your workplace!

  12. Coefficient of expansion of gasoline is 950 parts per million per Kelvin (http://en.wikipedia.org/wiki/Coefficient_of_thermal_expansion).

    Average daily variations are maybe 15 Kelvin (http://www.physicalgeography.net/fundamentals/7l.html).

    Underground tanks will have lower temperature variations, say 10 Kelvin. So you may save 1%. Drive 12,000 miles a year at 30 mpg, $3.00 per gallon, I’m thinking around $12 per year. There are easier ways to save money.

  13. Filling up before sunrise is a myth. The tanks are buried about 6 feet deep–about the same depth “geothermal” heat pump lines are buried. At 6ft., the temperature is nearly constant.

  14. Ha!
    “Invest in some new spark plugs – Spark plugs work in the most hostile of settings. If yours has over 30,000 miles than it’s definitely the right time for changing them. New and clean spark plugs are not covered in carbon deposits which means less fuel consumption.”
    If your plugs are covered in carbon deposits, there’s something badly wrong with your engine. De-coking engines ceased to be a regular task by the nineteen sixties.
    Also, I live in England, so I’m not sure what sparkplugs cost in dollars. I’d be very surprised to find a set at the “under $5” the header quotes.

    They missed out another good tip. Drive a modern, intercooled turbo-diesel. Okay, it’s above the $5 mark again, but diesels are inherently more fuel-efficient, and over 70 mpg is commonplace.
    I know, in the U.S., there’s a belief that diesels are loud, rattly, smoky, and slow. It’s no longer the truth.

    1. Well, what they don’t mention is that if you keep your car in good tune, you can get 100k from a set of plugs if you’re driving a car with a modern ignition system.

    2. “Drive a modern, intercooled turbo-diesel. Okay, it’s above the $5 mark again, but diesels are inherently more fuel-efficient, and over 70 mpg is commonplace.”

      European diesel engines are almost universally banned in the US because of pollutants. Europe never caught on to the nitrate pollution == acid rain thing and now Sweden and Greece are dissolving. The US is the opposite, don’t care about carbon pollutants, but stringent nitrogenous pollutant controls. I think Canada is happy about that since the lakes up there aren’t in danger of all the fish turning into black paste.

      1. Most of Sweden’s lake acidification is down to sulphuric acid from coal-burning power generation, England’s Drax power station is one particularly filthy offender.
        Diesels have cleaned up dramatically in recent years, but the main offenders in the diesel pollution stakes are the heavy haulers. Truck engines are often deliberately set to overfuel in order to give power at the expense of emissions, also diesel engines last longer (in the U.S., i seem to recall an average lifepan of 25 years for a truck or tractor engine), meaning the dirty ones of earlier legislations are still in use.
        Check out the EPA/Ford developed diesel engine to see what can be done.

        As for Canada, and black paste, let’s not forget the pollution from exploitation of Alberta’s tar sands.

      2. @ #23

        diesels are banned in Greece. in big cities only taxis and trucks are allowed to be diesel. outside the cities only vehicles registered as professional, so you cannot use them as normal cars.

        the diesel ban started in the 80’s as you said for pollution but has nothing to do with pollution now (modern diesels are pretty much as clean as gas engines). they are banned because we have a massive problem with contraband diesel.

        fuel meant for residential heat or agricultural machinery has lower tax but is often sold for vehicles at great margins. sounds absurd i know but they loose billions in taxes as it is so the government is in no hurry to loose more with the introduction of millions of diesel cars, despite big automakers lobbying.

    3. Even better: drive a modern, turbo’d diesel with a semi-automatic transmission like the one Citroën offers in their C4 (small family) hatch/coupe. In the first 13,500 kilometers I’ve averaged about 48 US MPG with a good mix of both city and highway driving with (almost always) two or three people in the car and belongings.

      That being said, I drive once or twice a week, tops. The longest I’ve gone w/o driving was about two and a half weeks. I use the bus and trams most of the time and, occasionally on a night out, a taxi home. I think that’s the easiest way to save some cash. Living in Poland, the cost of diesel here is cheaper than almost anywhere else in the EU27 and it’s still $4.75/gallon. Parking is about $7/day where I work. An all-bus, all-tram, all-times monthly ticket is $30.5. Despite all that, my wife and I would find it hard to live without our car, even though it is very expensive to have one here.

  15. @saskplanner Actually, for most driving, you’re not doing any good by coasting in neutral. Engine speed as reflected by the tachometer is only a measure of ignition events or engine rotation, not a direct measure of fuel.

    Since the advent of modern fuel injection systems, cars will shut down the fuel injectors during coasting or adjust their pulse width down to a level that just keeps the engine from dying. In the end, coasting with your foot off of the gas in a fuel injected car probably uses as little or less fuel than idling the car.

  16. @ Dave #7
    Yeah, the deep knowledge from that article does not fill one with confidence in that onlineengineeringdegree, does it?

    The above comments are pretty accurate. Don’t bother following the tips as they betray a lack of understanding.
    The “just before sunrise” one is particularly easy. All modern or semi-modern gas stations have HUGE underground tanks. The ground temperature is pretty stable, and fuel has a pretty high thermal mass (heat capacity) so even if there were significant changes in ground temp it would not make a huge difference to the fuel.
    Physics for the win!

    “Dirty air filters will disconnect the engine’s air supply”
    What kind of retard wrote that?
    There is a difference between “disconnect” and “block”.
    A VERY dirty air filter will cause the engine to run slightly rich which will use more fuel (usually also add a little colour to the exhaust). HOWEVER air filters are (most of them, anyway) are made from fibers with some oil on them. They can look black, but not really be blocking airflow. Take your filter out, knock it a couple of times inverted on something hard and see the ash particles fall out, then put it back into the car. Save lots of money and keep your car running fine. Only replace air filters every third time you change oil on your car.

    Overdrive- cruising destination.
    Ok, someone needs an editor. They mean cruising SPEED.
    And don’t forget to disconnect overdrive if you need to make large speed changes.

    Spark plugs.
    If your old spark plugs are covered in carbon deposits then the engine probably needs a tuneup. Oh, and you may need to not drive like an old person all the time. Carbon deposits accumulate on sparkplugs due to incomplete combustion. Often done by accelerating very slowly, driving in too high a gear and other such old person (or super-saver) styles.
    Run the engine up to red-line (RPM) regularly. Don’t use high RPM as a normal driving mode, just go up there once in a while and only when the engine is hot (been driving for at least around 15 minutes)

    The only thing that guy got right were a few super common sense things and the last point. Don’t use fuel saving products. They’re all scams. The car manufacturers will include any technology that allows them to sell more cars, and that includes stuff that really makes their cars use less fuel than the competitors.

  17. Honestly want to know a really great way to save gas? Drive more slowly, at least in my V6 if I keep it under 60 I get a 10-20% reduction in gas usage.

  18. Get a standard transmission – when I coast I shift into neutral to get the RPMs down as fast as I can, I accelerate slowly and then shift into 5th from second most of the time to keep the revs down unless someone is on my tail.

    I figure out my fuel economy EVERY fill. With almost COMPLETE city stop-and-go driving ( rarely go on the freeway) I’m coaxing 35-36 MPG with my ACURA…

    Or a well designed CVT. Keeping the engine at the ideal RPM regardless of speed will get you better mileage than even a standard gearbox can.

  19. I have a feeling there is a much better treatment of this subject somewhere on the uberweb. Please note that if you make use of your overdrive gearing when you reach your cruising destination you may overshoot.

  20. The early fillup is a complete myth. Not only are ALL gas stations I have seen in the last 5 years compensated to 21 Celcius, but the stations actually jack up the prices in the morning! They do this because people panic on their way to work when they see the “E” indicator and will buy no matter what the price.

    Allways buy later in the day!

  21. Or you could buy a motorcycle, which vastly increases your mileage.
    Ooh, or you could buy an electric motorcycle (you can buy these for under $10,000, so don’t complain about cost).
    Or you can power a bicycle with an electric motor and some lead acid batteries (which costs maybe $500, but distance/power is limited).
    Or you just ride the bike (which is no more efficient than an electric bike, but lets you exercise).

    None of these are really valid if you need to haul around a family of four or a camper, but most of the time, you only have one person to a car anyway.

    Basically, use a vehicle that suits your needs.

    1. Basically, use a vehicle that suits your needs.

      I need a car when I need a car, but I don’t need a car that often. I drove about 1,500 miles last year. When are we going to have effective vehicle sharing?

  22. Keeping your RPMs low is definitely not the best way to make sure your getting the best mileage. Three words: manifold pressure gauge.

  23. @arikol: Will a dirty filter really make the engine run rich on a modern car? I don’t think it will. My oldest car uses a vane-type air flow meter and my newer car uses a mass-flow sensor. Both measure the amount of air going into the engine AFTER the air filter so they should be unaffected by any restriction (within reason) before the flow meter.

  24. @#30 – There’s no reason to buy an electric motorcycle/car unless you know precisely the emissions that your electficity source generates relative to gasoline. In many places, particularly in the US, you could end up with more emissions coming from driving a plug-in vehicle because instead of burning gas, you’re burning coal, and factoring in transmission losses and the efficiency with which your battery charges, well, you may even be less efficiently using energy as well.

    1. If you’re only worried about emissions, yes coal power is probably worse off. But as for efficiency, electric motors have far superior efficiency when compared to internal combustion engines. Internal combustion engines lose some 85% of the energy from the fuel, while electric motors lose less than 20%, their chargers lose less than 20%, AC power lines lose less than 5% and even an oil power plant only loses around 60-70%.
      That’s right, an electric car powered by an oil power plant is more efficient than a car powered by an internal combustion engine.
      And besides that, many people are just as worried that we are using a limited resource as that we are releasing emissions. The world supply of coal exceeds the world supply of oil. It is cheaper, but unusable in cars. If batteries are affordable, they win in economy.

      And at least where I live, the electric companies have optional wind power plans for a 10-20% price hike compared to their normal coal. So you can have your cake and eat it too.

      But once again, I restate my earlier point. “Use a vehicle that suits your needs.”

    2. I agree jtf, but as a rule of thumb, in the US, electric wins. And it will not belong before it is true in all cases.

      FYI, the answer is to coat the planet in ‘PV too cheap to meter,’ This answer will happen. The only limiting factor are the factories, which eventually can be entirely powered by the product they create. PV is 100,000 times more efficient as nature at producing useful work from sunlight. A million years of biomass? 10 years of PV.

      Imagine the path that man will take as we conquer the sun. Imagine what we will think of the people who opposed this plan when we have the hindsight to recognize that the first leaps are always the greatest.

  25. @32, Antinous:

    I really want to make car share work, but I cant. At least not from companies rather then some type of friendly negotiation. I have hourcar and zipcar for $10.33 and $10.03 total cost per day for my driving habits of 1.04days/wk and 37.7 mi/per trip-day based on 5 yr of data. On the other hand, the total cost of my two saab 900s + fuel + maintenance + insurance is $5.88/day as a 5 year average.

    I’m convinced the share car will never be a better deal. I have been watching zipcar for 2 year and hourcar for maybe almost a year. I feel that zipcar would always have cars when I need them and they are conveniently located at my work (University). Hourcar only has 23 cars, but they have locations near my home and work where they park 1 and a few cars respectively. I am not convinced these cars are available for me (1 day/wk). I’ve never even seen the car supposedly parked near my house on more than 20 trips. Bike trips that is :D

    I pay $6/day to have a car I can use any time immediately, emergencies, or anything. I’m not sure where I sit in terms of average driver, but maybe you can compare to the above data. Basically, I use the car about 3 times per month to visit family and run errands and 1.05 times per month for an unplanned trip.

    The cost is not the main issue, but it would be more important with a less regular driving schedule. For me, the cheapest way to operate both programs is to lump as much driving together into a ‘daily’ session, which is basically what I already do. So anything else would cost more.

    I am also not sure how to place a value on having a car instantly accessible. My car driving is pretty regular (1day/wk), but when I do spontaneously need a car it is for worthwhile reasons (work, rescuing/helping friends, etc). Last week I had to take some samples out to a company on short notice. I could have gotten a university car or rental car, but my personal vehicle was 1000 times more convenient. My saab also hauls sheet rock and 36″ wide doors, which was nice as I fixed up my home. I have not added the cost of renting a truck in the estimated 10 trips I made with construction goods with my saab, which has the hauling capacity of a boxed light duty pickup, but that would probably have totaled about $400 for truck rental or delivery (about the same cost) assuming I could handle 20% of the trips in a rental car.

    P.S. I all this is based on calculations as of about thanksgiving and I know this is ridiculous LoL.

    P.S.2 I have spent $6400 on 2 very old (1992 and 1990) saabs because I love them (Did I mention I own the car of my dreams LOL?), but I think if you are purely concerned about reliability and low cost that there are cheaper options, like an older corola or civic.

  26. Wait, someone on the internet admitting they were wrong? Maggie, this won’t do. Yell, insult them, invoke Godwin’s Law, SOMETHING other than apologizing.

    And by that I mean: <3

  27. In the mean time, nice shot of one of my favorite plants. Nature is brutal. Nature is also hungry most of the time.

  28. I admire your forthrightness, however best practices usually dictate that you update or add an addendum to your first post rather than deleting it wholesale.

  29. @HotPepperMan #49

    MK-B is a contributing editor to boingboing not a guest blogger.

    Talk about standards and oversight… ;)

  30. Ack. The anger is disproportionate. The source of the article is not great; nor is I09 a great source for literary criticism, or any sort of criticism for that matter. But both are fine as grist for the mill, and neither gets me hot and bothered. I appreciate a broad range of sources and my brain is my own filter.

  31. I think it would have been more “boingboing” to leave the original article and append it with a “PRESENTED FOR ENTERTAINMENT VALUE ONLY, EVERYTHING HERE IS WRONG”

  32. @Saskplanner and most anyone else with a Honda, Acura, or other modern car…

    If you have a standard transmission, DO NOT PUSH IN THE CLUTCH OR SHIFT INTO NEUTRAL when coasting. You’re actually wasting gas vs. coasting in gear.

    Here’s why:

    The ECU will detect if the RPM is high enough at zero throttle and TURN OFF the fuel injectors. You use no fuel at all as long as your road speed can keep the engine from stalling.

    When the RPM dips close to idle, the FI starts again. So, if you push in the clutch or shift into neutral, you’re forcing the fuel back on!

    If you have an automatic or CVT the transmission handles this for you… but you might want to downshift into ‘D3’ or ‘S’ when slowing while downhill or in stop-and-go to keep the revs a bit higher.

    I have a ScanGauge in my car, and when coasting, it reads 0.0hp / 9999MPG. No power, infinite mileage.

    1. What everybody who goes on about modern EFI systems and their ability to use no fuel when coasting seems to miss (including the guys on Top Gear), is that it’s not actually coasting. Using the clutch or shifting into neutral is coasting; merely lifting off is engine-braking.

      I can roll down Melbourne’s Westgate bridge at a constant 80km/h (the speed limit), but if I merely lift off, I slow down thanks to stuff like valve springs and compression ratio.

      If you’re so keen on using zero fuel sometimes, you could disengage the clutch (if you have one), switch your engine off and back on without starting it, happily roll with only air resistance and rolling resistance slowing you down, then engage the drivetrain to start the engine again.

      Mind you, that’s pretty dodgy and probably illegal because you lose vacuum assist for the brakes, and power steering if you have it…

      The only way you could truly coast by merely lifting off is if your engine used something other than a camshaft to actuate your valves, and left them open in that situation.

      You know what would save a hell of a lot of fuel?

      Manufacturers offering cars that weigh less than 1000kg again. My ’85 Exa (NX Pulsar in the US) is 900kg, slices through traffic, is a doddle to park, and is well-packaged enough to accommodate four adults and quite a bit of luggage.

      What happened to such cars?

      …By the way, I’m loving that adjective, ratfuckingly.

  33. Maggie, I have tried your method and the venus flytrap farm on the back seat of my car is working as a source of organic fuel. I find it difficult to harvest enough Scutigera, but find driving into a horde of Mayflies with the windows down quite rewarding. Alternatively, leaving ripe bananas under the seats allows one to acquire all the drosophila you need. Thanks for your help.

  34. Damn – I would have really liked to see the original article; the conversation sounds really interesting.

    This is a feature of internet publishing I don’t like: When authors make retractions, they often delete the original, creating “orphan” conversations and robbing future visitors of the opportunity to learn from the original discussion. Perhaps a search-engine-blocked version of the article, linked from here?

    1. Yes, but, a 400 comment thread where everyone gets to make easy or angry points against an ill informed linked article is no way to run a good website, either.

      That article read like a bunch of bad strawman arguments IN FAVOR of conservation, which could easily be used to discredit the goal. It was ratfuckingly bad, probably published by someone who wanted to misinform.

      I’ve never seen BB do it before, and I really am glad this article was pulled. Thanks Maggie. Good call.

  35. “…don’t coast in neutral…”

    On the other hand, if you can coast on momentum rather than giving it gas for a while, that’s a win. I do this on long low hills or at the end of a hill followed by a big flat followed by another hill, etc. ..

  36. If you drive at all, here’s how to save gas:
    a) drive as little as possible- combine trips, etc.
    b) accelerate and brake gently
    c) drive something fuel efficient or at least with enough gears to keep RPMs down at highway speeds.

  37. Will everyone please stop insisting that leaving the car in gear and coasting will save gas in a manual transmission car?

    While it is true that modern cars shut off the gas to the engine in this situation, whether or not you save any gas is highly situational. It turns out there’s this thing called engine braking that is causing your car to slow down when this happens, which is great, but whose to say you couldn’t have saved more gas by putting the car in neutral earlier and coasting a longer distance?

    It’s entirely possible that the gas saved during engine braking is more than outweighed by keeping the engine running at speed for a longer time. It just depends on the circumstances.

    Sometimes leaving it in gear is better, and sometimes coasting is better, but there’s no surefire answer.

  38. I didn’t rtfa, but here’s a tidbit. Fuel oil companies load heated up oil into the tanker trucks, so when it’s pumped into the homeowner’s tanks it has a greater volume. I’m not sure that all gasoline delivery is done this way too, but I know some stations that won’t accept morning deliveries; they insist that they get late deliveries in the hopes that the fuel will be cooled off by that time.
    The pump may compensate for the temperature, but your furnace sure won’t.

  39. I always put my car in neutral at a stop light. I don’t know if it makes a big difference in the amount of fuel that your engine is using, but I was taught that it’ll minimize the damage to your engine if you get rear-ended.

    1. It’ll allow your car to go flying into the middle of the intersection so that you can be conveniently broadsided by cross-traffic.

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