Your Gas Tank: Do You Top Up or Not?

Discussion in 'Community Discussion' started by HappyDude20, Dec 11, 2010.

  1. HappyDude20 macrumors 68030


    Jul 13, 2008
    Los Angeles, Ca
    This is something that's been subconsciously on my mind for a while now and figured bringing it to minds of others to discuss it could potentially leave me with a more informed decision when at the gas pump.

    Sometimes I fill my gas tank up completely, while other times i'll fill up the gas tank only half way. Other times, rarely, i'll only add a gallon or two at the pump.

    Sometimes the reason is money. If I find a gas station where the price is super low and my tank needs filling up, I'll add the whole 14 gallons to my Altima, which for most of 2010 gets filled up completely with about $40.

    Other times when the gas prices aren't that appealing, but need gas and perhaps don't want to make another gas trip visit i'll fill her up half way, so about 6-7 gallons for about $20. <This option seems to reoccur the most, except in the summer months when I usually fill the tank up completely due to driving a bit to the beach.

    & then there are the rarer times when I need gas but am either dead tired, or dead tired to get home so i'll stop by a gas station and simply add a gallon or two in a hurry. This situation also may occur when there's only one gas station in the area with higher prices.


    The reason I felt like starting this thread was simply cause I remember hearing that filling up the gas tank completely is most beneficial for the car, and also in terms of getting the most mileage.

    If I filled up my gas tank completely on a Monday, it would most likely last me for a week and a half...for $40. While this week I added $20 on monday, needed gas earlier tonight (friday) and added $10. $30 total this week, and then some.

    Of course, all this is the intended wanted outcome of spending the least amount for gas. $30x4= $120 on gas a month...

    Iono, just figured i'm not the only one that has a personal mantra when it comes to filling up their car. :p
  2. Watabou macrumors 68040


    Feb 10, 2008
    United States
    Well the more gas you have, the less mileage you actually get because of the added weight obviously. I haven't really tried that though because I get around 32 mpg which is good enough for me.

    I fill up my gas to the full because I'm too lazy to go back and fill it up again. Plus, I always fill up at Costco which is the most crowded gas station here...but, on the other hand, I get my gas at $2.9-3 per gallon which is pretty nice considering I only fill up every other week.
  3. VPrime macrumors 68000


    Dec 19, 2008
    London Ontario
    When I was working I would fill up to the top..
    If I was going to the track to race, I would usually fill up half way.. Or just enough to get me there and back :D

    One thing to take note of is on most cars gas lubricates and cools the fuel pump. So leaving it empty, or very low on fuel can cause your fuel pump to fail prematurely :) So don't leave your gas tank too empty!
  4. HappyDude20 thread starter macrumors 68030


    Jul 13, 2008
    Los Angeles, Ca
    I remember thinking the very same thing..though never found any proof supporting this claim.

    It makes sense in a way, for some reason I also thought that the less gas, say having only 2 gallons as opposed to a full 14 gallon tank, the car will go through the gas a lot more quickly...kinda like the last water in a sink in a spiraling funnel; the funnel picks up speed and really gets rid of the water most quickly at the very end... Though this sounds like a drunken thought, aside from having no proof at all to this theory that may or may not even make sense, has come to my mind once or twice.<<<<<<< This paragraph doesn't make sense, and it's also one long sentence. I apologize.
  5. eawmp1 macrumors 601


    Feb 19, 2008
    Electronic fuel pumps use the gas for cooling and lubrication. In theory running on empty could cause problems. There is an old theory that if you run on empty the sediment on the bottom of the tank is concentrated and could foul the engine. As the fuel pump always sucks from the bottom and with the modern fuel filtration, this is probably bunk.

    Your car weighs less when tank is less full, so you will get better mileage as the tank empties.

    Filling the bottom 1/2 of the tank costs the same as filling the top 1/2, so unless one lives paycheck to paycheck, there is no economic benefit to not filling up.

    And NEVER top off tank after handle clicks - wasteful, bad for environment, and can block vents.
  6. Hellhammer Moderator


    Staff Member

    Dec 10, 2008
    You have cheap gas. It's about 1.5€ per liter in Finland so 14 gallons (~53 liters) cost around 75€ (100$). I don't drive that often as I don't have my own car yet but I sometimes borrow one of my parents' cars and use that. If I have to fuel it, I never fuel it to the top because both cars have like 80L tanks so that would cost me 120€ to fill it, yuck!
  7. takao macrumors 68040


    Dec 25, 2003
    Dornbirn (Austria)
    obviously having a full tank has to use more fuel simply because of the weight

    on bigger cars with 60-70 liter or more tanks it's the same as riding with a passenger

    that's also an explanation why many modern cars have a lot higher 'empty weight' than 20-30 years ago because it's simply calculated differently

    in europe for example the "empty weight" includes a 75kg driver and a 90% full fuel tank
    in the US the "curb weight" includes a full gas tank but AFAIK no driver
  8. VPrime macrumors 68000


    Dec 19, 2008
    London Ontario
    It really depends on the car. My car, and quite a few others I have worked on will kill the fuel pump on empty.
  9. r.j.s Moderator emeritus


    Mar 7, 2007
    I fill up every time. Why not, adding a little bit just means I'm going to need more soon.
  10. Doc750 macrumors 6502a

    Aug 11, 2010
    I never put this much thought into it. I fill up at the cheaper cash only station on my way to work.
    If I cant get to cheap gas station, then I fill up anywhere.
    On the the gsxr, I try to only go to shell. It's that damn marketing they do.
  11. tunerX Suspended


    Nov 5, 2009
    I fill it until the handle releases, usually.

    Sometimes I can't though, running a CC through the pay at the pump limits you to 75.00. A 26 gallon tank and the right fuel price sometimes means I am a gallon or two shy when I hit the limit.
  12. Mr. McMac Suspended

    Mr. McMac

    Dec 21, 2009
    Far away from liberals
    I always use self serve and fill my tank completely.
  13. dllavaneras macrumors 68000


    Feb 12, 2005
    Caracas, Venezuela
    I always top it off. The only reason for not doing so is forgetting my wallet. Gas is so ridiculously cheap (a full tank of gas costs about a dollar) that we always top off the tank.
  14. Phil A. Moderator

    Phil A.

    Staff Member

    Apr 2, 2006
    Shropshire, UK
    That's about what it costs in the UK - current price is between £1.15 and £1.25 per litre (1.37€ to 1.49€) with prices set to rise again in the new year. It's even more expensive on the motorway (over £1.30 in some places) so if I'm caught short of fuel on a motorway I tend to just put enough in to get me by and then fill up where it's cheaper

    I had to do a double take there to realise you were talking about a dollar a tank not a gallon (which would still be incredibly cheap!). Is it subsidised by the government?
  15. rdowns macrumors Penryn


    Jul 11, 2003
    I fill the tank every Sunday morning. I have better things to do than drive around looking to save 3¢ a gallon or topping off my tank. I do top off the tank if a snowstorm is expected.
  16. iMpathetic macrumors 68030


    Oct 7, 2007
    I generally top my tank off... although a 25 gallon tank that needs premium is one hell of a hit, especially at 7-8mpg around town. :eek:
  17. Mac'nCheese macrumors 68040


    Feb 9, 2010
    I've also heard that the more air that is in your tank, the more pressure is on the gas, sending it through the engine faster. That is why when you fill up, you notice it the needle takes a bit to move down but when you are close to empty, it moves down faster. I have no proof of this, just something I've heard before. I also live in Jersey where its against the law to pump your own gas so I have no say in the matter.
  18. QuarterSwede macrumors G3


    Oct 1, 2005
    Colorado Springs, CO
    That makes no sense. Air is a lot lighter than gasoline and modern engines have some type of fuel injection which negates any pressure the gas has anyway.

    I never knew that. What an outdated law!

    As far as what I personally do, I fill 'er up to full. I've never understood why any wouldn't unless broke. It's not worth the time to save a few pennies (which you're probably wasting by driving to another station) to go to a cheaper station.
  19. Btrthnezr3 macrumors 6502a


    Aug 5, 2010
    Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_2_1 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8C148 Safari/6533.18.5)

    Letting someone else fill my tank would bug me to no end. I couldn't handle some greasy embicile scratching paint or dripping fuel on my baby.

    I usually fill up all the way but I've got an 11 gallon tank and get 40+ mpgs so it's not too often.
  20. steve2112 macrumors 68040


    Feb 20, 2009
    East of Lyra, Northwest of Pegasus
    I just wait until I'm around 1/4 tank or so and fill up. I'm at a point where I can afford it, and I don't feel like dealing with it any more often than I have to. There is a Sam's club about 2 miles from my house that usually beats the gas stations by about 5-10 cents a gallon, so I usually stop there. Kroger has this thing where if you use their "loyalty card" and spend $100 on groceries, you get $.10/ gallon off their gas. It's usually so crowded though, that I don't use it.

    Of course, back when I was in college and had a V8 powered Oldsmobile that got about 12MPG, it was a different story. It was fun trying to scrape together enough money to feed that beast.
  21. Moyank24 macrumors 601


    Aug 31, 2009
    in a New York State of mind
    I went to college in New Jersey, and coming from NY I thought that was the greatest law ever! Especially in winter.

    To answer the OP's question, I always fill up the tank. A tank will last my truck most of the week and I work until 1AM so I don't want to have to put myself in a position where I'm searching for an open station in the middle of the night.

    There have been a few times when I've opted only to put a few gallons in. I work downtown and it always ticks me off that it can be up to 10 - 15 cents/gallon more than around where I live. Not a lot of $$ obviously in the scheme of things, but it annoys me. I understand about higher rent and location and stuff like that, but DAMN, that $2 I can save may go a long way sometime. :D
  22. sushi Moderator emeritus


    Jul 19, 2002
    Always fill up.

    Criteria: Each week or when it gets to half. Whichever comes soonest.
  23. einmusiker macrumors 68030


    Apr 26, 2010
    Location: Location:
    I always fill my tank in NJ, where the prices are a good $0.30 less than NY. If I absolutely have to get gas in NY I only put $10 or so in. My Murano AWD is a bit of a gas guzzler unfortunately and I drive a LOT :(
  24. ucfgrad93 macrumors P6


    Aug 17, 2007
    I almost always completely fill my tank. The only time I don't is it is really cold outside or I'm running late for an appointment.
  25. Mac'nCheese macrumors 68040


    Feb 9, 2010
    Yeah, when you put it like that, you know, using facts and stuff, it does sound silly but I swear I've heard it from a few people. Maybe they are so old, it was before fuel injections. The NJ law is great in the winter but sometimes, in a rush, its silly. We still have much cheaper gas then other states, though. Probably be even less if they didn't have to staff the pumps.

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