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Thread: Better MPG when filling up sooner?

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Posts: 11-19 of 19
2010-09-07 05:22:44
#11
mine does the same.
2010-09-07 22:55:44
#12
Yes, all cars do this to some extent. And it has to do with the vapors. Gas likes to evaporate, and the engine will burn these vapors as part of the EVAP system. But if you fill up before going below 1/2 tank, you should see a couple mpg or so.
2010-09-07 23:22:38
#13
We had a similar discussion in one of Vadim's threads about MPG's I believe. The main reason that I can think of is, like a few have already said, the vaporization of the fuel. If you fill your tank from empty the fuel gets splashed around in your tank and vaporizes more as you are pumping. Vapor is wasted fuel. Conversely if you have above half a tank of fuel there is not as much loss due to vapor from the splashing. By all rights you are not actually getting better miles per gallon, as the fuel used to move your vehicle is still the same most likely, but you will most certainly get better "miles per dollar." There are a few other tricks to help with this as well such as pumping the gas into your tank slowly.
2010-09-08 04:54:27
#14
Very good point on "miles per dollar" idea gunnartalon! Though I should say, since we don't have any real accurate MPG calculators besides the gas pump, we are stuck with saying Miles Per Gallon as per what the pump says.

This is why it's important to use the same gas station and pump, to eliminate any pump inconsistencies.

Now another interesting thing that I've noticed, I use Shell gas 99% of the time. It doesn't seem to foam as much as other gas when I fuel it up. Last time I went on a road trip I was forced to use a Hess gas station. It foamed going down like no other. Which caused the pump to hit out early, before the tank was full. Which made my MPG's seem high on that fill, but then very low on the fill after.
2010-09-08 18:02:41
#15
I'm also wondering what the fuel gauge is doing in my B13 Nx. I just replaced it for a know good one because the one I had was quite off, would seem stuck, pointin a little low, dropping soon, not dropping for 70 miles and that was obviously the sensor in the tank.

But still, I can agree the gauge seems to drop fast the first half and the other half seems to last longer. I also have issues with resetted ECU's (and there are different ways of resetting just one really works, leaving the car overnight without battery, bc I learned 20 minutes just empties error memory leaves issues like my ticking AAC and then I left it battery less for 2 hours and ticking was gone, which I wasn't able to before.

To keep the long story short, I don;t even trust the ECU no more, after a good reset tank seems to last longer. Then when I fill it up to max, mileage seems to suffer. Yet, I can't proof this.

Also be sure to fill the tank way up, and use the trip meter for good measurement, so you need to squeeze in that last liters where it overflows all the time. Else you cant be sure you filled to the same level, even with same gasstation and pump.
2010-09-08 18:18:52
#16
Originally Posted by XxToKeSxX
It's not necessarily a problem... just the way the fuel gauge reads... check it.

This isn't exact, but if you can - picture your gas tank as a closed weir cross section or something...If the bottom width of the tank is smaller than the top width, and the tank level measures the height of the liquid level, the reading isn't necessary linear.

In other words since the liquid level is read from the dial, and not the volume... since the bottom of the tank is angled, the reading will not be linear on the gas gauge. At half level, its not necessarily the same amount of gas as the top half of the tank... which is why it would seem to deplete faster... That is most likely why. If not then sue me.





^From the OG forum.

Gas guage after half tank - SR20 Forum

^Thread link.
2010-09-08 18:21:45
#17
^ makes sense/since/cents/scents




lol
2010-09-08 18:36:13
#18
^ that does make sense
2010-09-08 22:25:50
#19
Dang, the desigener could have adjusted the sensor of the fuel gauge for this :P
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