PatrickGSR94

iTrader: (1)

The auto shut-offs on gas pumps, do they (different gas stations) all shut off at the same point on our cars? If not, then how am I supposed to make any mpg calculations if the gas doesn't come up to the same level every time I fill up? I know most of the pumps around here say "do not top off" but I swear it doesn't fill mine up. Tonight my gas light was coming on, needle almost to E, 290 miles since last fillup. I stuck the pump in and turned it on, and it cut off at only 8.79 gallons. Now 290/8.79 is about 33mpg, which would be awesome, but my needle did not make it all the way up to F, so I'm pretty sure I got somewhere around 30mpg or less on that last tank. So what is there to do? Is there any good way of calculating MPG, or at the very least, making sure the gasoline comes up to the same level each time I fill up?


[Modified by PatrickGSR94, 11:58 PM 7/22/2002]

laseca

I measure my GSR's mileage all the time and to do it accurately, I top off my tank all the time. I found a gas station that has pumps that don't have the rubber accordion type hose around the filler nozzle and allow fuel to flow out slowly by modulating the fill lever. When the pump clicks, I can get up to another gallon in the tank. Being patient, it may take about two minutes to top it off until the fuel level stays put at the filler neck. My fuel guage goes beyond the "F" mark and doesn't budge till about 90 miles or so of freeway driving.

Yea, yea, yea, I've heard stories where you're not supposed to top off your tank since since the fuel needs to expand should it be a rather warm day. I top off my tank and immediatly drive about 70 miles so I've already used up at least two gallons. I've been topping off my tanks on all my cars for years and no problems. I believe the warning of not topping off your tank implies that fuel will splash out. That's true if you get an on-off style pump and not a slow flow type.

I've got a '01 GSR and combined city/hwy driving, I get about 28MPG. On longer trips, I've gotting above 34MPG cruising at 70.

Paul

mskibbz-T

Maybe go to the same pump at the same station... other than that I can't think of anything.. I'm sure different brand pumps shut off at slightly different points, but at the same time they are all trying to put the maximum number of gallons in your ride to maximize sales so it should be relatively close. Did your needle go to F after driving for a few minutes? Do you really need to know the exact MPG? You could go to the extreme and weigh your car with a full tank, drive it off w/o changing anything that affects weight, reweigh your car and do the math, but even that wouldn't be completely accurate because of all the other variables tossed in the mix... I don't think you can get a 99% accurate result no matter what you do.

Dutchie

Pretty tough to fill it up the same every time. It is way more accurate just to write your mileage and litres (gallons in your case) down and average it. Just figure it out every 8 fill-ups or so, and you will get much more accurate numbers.

Asahi

Patrick

If your gaslight was on you should be seeing 10 gallons easy. Tank is 12 gallons and there is a safety amount for the light.

I think the same pump and the same station will cut off very differently. THey aren't there for accuracy just safety.

I would top it off but do it carefully.

kinesistech

I just fill it every time and check my milage, then divide milage by gas pumped and you'll be good.

ingrate

like someone said earlier, just use the same pump for consistency

PatrickGSR94

iTrader: (1)

Yeah I was thinking that it cut off rather early... the tank is actually 13 gallons, I got almost 11 gallons in there the other day WITHOUT topping off!

zilverz

Hmmm what about ...


Filling up gas ..right when the gas light comes on (as long as you were not on an incline/decline when the light came on) and fill it up a certain amount ... say 9gallons even .. reset the trip counter ..drive it till the gas light comes on again .. and when it does ... write down the exact mileage and do the math .. that should get ya close enough to the real figure

(as long as your fuel sending unit isnt out of wack) (;

redintegra

People, its really simple ok. Next time you go to pump.

1)reset your trip meter and pump your gas
2)drive
3)next time after when you pump, just divide mile on trip meter by gas pumped. Viola

Asahi

oops your right 13.2 I believe. Was thinking it was 12.8. Not even the same pump will be accurate. BUt taking the average like someone mentioned above is the best plan and if you can use the same pump even better.

Asahi

Gee, no ****? I think He has the Math figured out.

The question is how to verify accuracy of the pump cut off. Pumps cut off differently sometimes at 8 gals sometimes and 10 gals with the same empty space capcity. DOes that mean by your forumula I got better mileage when the pump cut off sooner?

redintegra

woops, thanks for setting me straight.
Yeah, there is no easy way to get downright accurate. Averaging will get you close
I even read a long time ago that some gas stations don't pump out the exact same amount because the operator can illegally make the meter go faster.

Asahi

now the illegal thing is a whole new can of worms!

PatrickGSR94

iTrader: (1)

WTF I've never heard of this

I'm trying to stop the top-off thing, after having my tank overflow several times (in 5 years of driving my Camry it only overflowed ONCE on me).

GSRaCeRbOI

its really more of an approximation for you to calculate approximately how many MPG your getting.. because each station and each pump will shut off at a different point...also even if you go to the same pump and same station its probably not 100% consistent... I usually fuel up and then top off... I reset my trip meter each time I fuel up and just divide the miles traveled by gallons fillled if I want an approximate MPG... I know its probably not all that accurate since even though I top off.. not sure exactly how full it is but it gives an approximation of your MPG....

I don't even bother anymore since my car is stuck in traffic all the time = (.. LA traffic sucks

Just_LS

A good way of calculating MPG is to average it. We now know the pump cutoff is gong to be different so the best way is to average it, say, every 5 times. Even the factory MPG is base on average so this method won't be far off. HTH

redintegra

Dateline or 20/20 or someone did a test a few years back on this illegal meter issue. Regulators check if meter pump exactly 5 gallons(was it 10? I don't remember) so they don't get in trouble with the law but pumping any other amount is a little off

GSRaCeRbOI

yeah I saw that.. I think it was Dateline NBC not sure.. they use special vehicles where there is a separate tank (2nd tank) and the vehicle doesn't actually use whats pumped into that tank to run itself.. that way they go to a station.. pump into the 2nd tank.. take it back to the laboratory and whatever is drained in the 2nd tank.. is whatever was purchased... then they compare the gallons in the tank to the gallons on the receipt/pump...or whatever.. I think it was 5 gallon purchases...

they showed some gas station owner w/ a switch that he can turn on or off behind the counter to either accelerate the pump/meter to reflect more gallons sold than actual.. or he could turn it off and it could be normal right?

samagon

the ammount of extra gas you get or don't get depending on how well the pumps are maintained is not enough to effect your mileage measurement.

I always just fill it up till the pump clicks off on its own, and I go to the same gas station every time, so that I have the least variance possible, but as I said, you are dealing with maybe 1/10th of a gallon up or down.

I round my numbers anyway

Asahi

If you notice he didn't even get 9 gallons on a 13 gallon tank that was showing the emptry warining light. That means he was 4 gallons till empty. Sounds unlikely. Pumps here click off and I can add 1-3 gallons at times after the shutoff.

4 gallons will make a huge variance in calculations.

Best bet is to be careful and top it off. Try not to spill.

PatrickGSR94

iTrader: (1)

I may try topping it off REAL slow until I can just start to see it come out.