Gas Mileage Question

Discussion in 'Lounge' started by Flyboy, May 22, 2014.

  1. So despite my Dad being the Lord when it comes to cars, I'm more like Leonardo Di Caprio's character from What's Eating Gilbert Grape. I understand enough to keep the wheels turning and enough to keep from having to take it into the service station for every little thing, but otherwise I'm a vehicular moron.
    So, here's my question; why is it that on an average week, I travel a grand total of 183 miles from home to work and back (I work four days in a normal seven day week) and my tank is completely empty, but yesterday I drove to South London and back, a 227 mile round trip, with the return trip being heavy two massive suitcases and a wife, and I use not even half a tank?
    I drive an '02 Honda Civic hatchback; while home, I rarely go anywhere that requires driving; where I live, everything is within walking distance. The only time I use the car to go anywhere other than work (lately; now that the wife is back, that will change) is to go grocery shopping, but I have five grocery stores within a one to five mile radius of my home, so it's never more than a two to ten miles round trip for grocery shopping.

    Now, the speed limits are more or less within ten miles per hour of each other for both trips; my trip to work, I average a speed of 60, maybe 70 or more in short bursts on the highway (I'm on back roads most of the time). The trip to London has me going 70 or more pretty much the whole trip as it's almost all highway. The trip to work has more twists and turns that require me to brake and slow more; the trip to London are a series of three or four straight shots for fifteen to up to thirty miles apiece.
    I'm just trying to figure that out. I was sure I was gonna be running on empty by the time it was time for the return trip, but no, I was actually still on a FULL tank when I got to London.
    Does that make sense, or do I have a faulty as Hell gauge?
  2. Bull

    Bull Just a Man Supporting Member

    Or ya got a petrol thief.

  3. duster066

    duster066 Supporting Member

    It's easy for me to understand but not as easy to explain. The answer is in the questions. Start them cold and they run rich. Stop and go driving burns more gas. It takes Something like 14 horse power to maintain a steady 35mph, but it takes 50 to get it to 35mph. Every time you squeeze the peddle an extra squirt of gas is injected to cover for the sudden add airflow. Engine speed eats gas through fiction. So going through the gears eats gas from all these things. On the highway the car is warned up, at a steady road speed and on overdrive so engine speed and fiction are low. All make it use gas more efficiently.
  4. My gas cap cover locks, and you'd need a crowbar to open it when closed. To unlock it you need to hit the locks from inside the car as well as pull the gas cover handle. I actually put a thin layer of faux paint on the inside rim of it, so that I can check to see if it's been touched since I last opened it; it's just a thin coat of latex paint; thick enough to stay on while driving, but thin to the pint where it peels like crazy when you touch it.
    That and it's always at the same level when I get back in the car after leaving it parked for long periods of time.
  5. lklawson

    lklawson Staff Member

    My car gets 40 rods to the hogshead and that's the way I likes it!

    Peace favor your sword,
  6. Liberty

    Liberty Shhh! Lifetime Supporter

    I drive identically to work and on trips. I average 22 around town and 38 on trips. Do you have cruise in that? Is it a VX? The VX is a BEAST for highway driving. Cruise control REALLY helps. It doesn't add gas like pushing on the pedal does. Slow and go, stop and swerve - those types of driving take a LOT bigger toll and take a LOT more to make up for. You might only be actually getting 10-18 MPG when you're hitting stop signs & lights, along with curves. To make up for 1 mile at 10 MPG you have to drive 8 at 40 MPG to average 30. Two basic onramps to drive 225 miles - you're doing fine.
  7. undeRGRound

    undeRGRound ROLL wif Da MOLE! Supporting Member


    That is pretty much it in a nutshell.
    Cruising at 50 MPH takes maybe 10-12 "road horsepower" and it is constant.
    The stop-and-go (or speed up,slow down) is what kills mileage. Plus, you have
    cold starts every day, and one long trip negates most of the thermal inefficiency.

    YESSIREE Member


    USMC_VET Supporting Member

    your lucky you get that MPG , for my Camaro it's single digit fuel mileage and i get a whopping 5mpg and have to really watch my fuel press gauge closely as once ther needle starts dropping on accel it's time to look fro a gas station
  10. Branth

    Branth Member

    Every time you tap your brakes, you take kinetic energy that you bought and paid for with gasoline, and you turn it into useless heat and friction through your brake pads. Stop-and-go driving is TERRIBLE for gas, and the same is true for driving where you slow down with your brakes a lot.

    Starting your car takes a surprising amount of gas, and I always thought that was why short trips get worse gas mileage, but Duster's explanation makes more sense and fits with the available data better, so I'll defer to that one.

    Combine the two, and you have the difference between "city" and "freeway" MPG's on your window sticker.

    Also, sharp accelerations REALLY kill fuel economy. Try driving like a grandma for a few days, and your efficiency should improve - Accelerate very slowly, drive the speed limit or below, avoid using your brakes when you don't have to, and your mileage will be WAY better.

    Re: your brakes - Of course use them when you don't want to run into people, but when the speed limit goes down, just coast down to the new speed instead of using brakes, and if you're in stoplights, try to stay relatively slow and coast down to a reasonable speed before stopping instead of accelerating until right before the light and then hitting the brakes.
    Last edited: May 22, 2014
  11. undeRGRound

    undeRGRound ROLL wif Da MOLE! Supporting Member


    Good post, the only difference I have are with the above... bold, italics, underlined

    Research with high speed data acquisition has shown that medium, moderate
    (approximately 1/2 throttle) acceleration is more fuel efficient than grandpa acceleration. You are using the more "power efficient" portion of the powerband of the engine, for a shorter period of time. Then you get to the highly efficient cruising range faster. It is engineering stuff, BSFC and all of that.

    The rest is all good for mileage, if not great!
  12. Tchort

    Tchort Member

    If you really want great mpg drive live I do in subs of Chicago, full size V8 ext cab Silverado 4x4 , drive it like I stole it. 55 zone....means 80-85. Light turns green race to next one. NEVER less then 8 miles over speed limit. Get about 14 mpg. Highway, maybe 17.

    Not like dumby (me), get bad mileage, no matter what vehical. Take it easy and drive Kansas style ( sorry, lived there, you guys definitly not in any hurry) get good mpg.

    Oh ya and besides gas we got all them dam tolls going to and from work $3.80 a day.
  13. duster066

    duster066 Supporting Member

    If you want some help there is a way to get it right on the instrument panle. But a vacuum gauge. They are super easy to install. While driving the object is to keep the vacuum reading as high as possible. I used to hate them, then had to drive the duster from here to Texas. I put one in for that trip and it worked. It became a game, never let needle go into the red and keep it out of the yellow as much as possible. It was worth about 5mpg. It works and after you've used it awhile you don't need to look at it all the time because your habits will have changed. They used to be a factory option. They were called economize gauges.
  14. ajole

    ajole Supporting Member

    NE Utah
    That's really, really bad mileage.:cool:

    My 300 HP Chevy gets 30 mpg freeway. You might want to modernize your power train.:p
  15. undeRGRound

    undeRGRound ROLL wif Da MOLE! Supporting Member


    Especially the Fuel Delivery System :p
  16. Back2School

    Back2School Member

    My modernized powertrain, 285 hp V-6 gets just over 20 mpg on the highway, but I have the extra loss of driving a front driveshaft and the aerodynamics of a brick :p
  17. i thought you guys used liters of gas and kilometers. Maybe that is the trouble? ;)

    I drive a '13 F 150 used to get 19.4 mpg, now I am I am getting 20.5. YAY ME! Dunno why though.
  18. ajole

    ajole Supporting Member

    NE Utah
    It's finally broken in?

    Odd thing about the way they measure mileage in Europe. We do distance per volume of gas, they do volume of gas per distance.
  19. I think it is mostly because I am not driving the grandkids to their bus stop and wasting gas on that 3/4 mile trip. Also summe mix might play into it.

    I am driving from Knoxville to Raleigh in about two weeks, I am guessing I will average about 18.9 on that deal.
  20. I'm American, so I use miles and gallons lol.
    Although the UK also uses miles; they are not metric that way. They do use liters though.