Fill it til it wont hold anymore

 

Tossing this in here... is it possible that when running into the final 1/4 tank, the needle moves a little fast compensating for the reserve? My '91 XJ seems like when it gets to the 1/4 mark, it starts going down a little faster, and if I wait until it's on 'E' to completely fill up, it seems 2-3 gals always remain in the tank (and no, it isn't the overflow as I don't sit there and pump-pump-pump until it squirts from the fill hole). Possibility, or maybe mine is just a fluke? Lol, idk.

 

When there is more fuel in the tank, the fuel that is in there is COOLER !!!

I had a cargo van that went through three in tank fuel pumps before a tech at the dealer asked me this question .....

How often are you running with LESS THAN one half a tank?

I told him I rarely fuel up over one half and more often it hangs at 1/4 tank or less.

He then informed me that the fuel in the tank cools the fuel pump and when running that low on fuel the fuel gets warmed up and can contribute to fuel pump heat related failure.

From that point on I kept the tank topped off and have never pulled a fuel pump since that time.

Oh and my mileage did improve a bit, but never thought about it.


On my 1996 XJ, 4.0 i6, 5 Speed, I routinely get 20 MPG but I use several tricks. The best trick is to COAST downhills, XJ in neutral. Saves a lot of gas.

 

Filling to the very top might flood your evap tube that runs to the charcoal canister. Not recommended.

The filer tube will back up when the tank end is submerged. A pretty slight difference in the angle of the tank can change how much air is still trapped in the tank when the end of the filler is submerged.

For the most accurate mileage figures, of course you would want the largest sample, after 50 gallons, after 100 gallons ect. (you don't really even need to know if it clicked, or exactly where the gauge is, until the final tally.) Just note the exact amount that went in. Of course a small sample could easily be pretty far off, but after 100 gallons, if you were off by 2 gallons, that would only be 2% (about 1/3 mpg).

Not suggesting you didn't know that, just putting it out there because you got an odd result, with what sounds like a smallish sample.

 

Also, being heavier would make any vehicle carry more speed down hills, say when totally off the throttle. more weight=more effects of gravity. Thats why pinewood derby cars have a MAX weight limit, the heavier the car, the faster it will go down the hill.

 

do you have the correct speedometer gear in your car for your tire size and gear ratio? that will effect odometer readings.


and also. i got nothin against doing this method for the most part.
but id say every few months at least you wanna drain it down almost empty.
or at least to 1/4. other wise 1 yr down the road you will still have gas in your tank from a year ago.. and gas can go bad.
just my .02 cents take it or leave it.

 

um, i dont see how you get old gas from filling it up at 1/2 tank. Does the gasoline naturally separates from its self from different gas stations?

 

Very curious. I like the idea of the fuel pump being submerged, I've read the same thing about keeping at least 1/4 tank in some vehicles to prevent premature failure. Hilarious that the most explosive thing in a vehicle is used for cooling...

Something to add is it's important to consider when you consider the tank "full". I just stop when the back pressure is high enough that the pump stops on it's own. This varies greatly between gas stations, but generally speaking if you use the same pump at roughly the same temperature every fillup then you should be pretty close to filling to the same amount. I dunno what the fuel gauge has to do with anything... you kinda have to have the key turned to Run in the Jeep to even see it and I'm pretty sure you wouldn't be welcome back at that gas station any time soon if they caught you.

Uhh might want to read up on how gravity and acceleration actually works. This was demonstrated a few hundred years ago by a guy named Galileo. Heavier weight of the tank would result in more momentum which may help prevent deceleration due to rolling resistance and drag going downhill. But it would definitely impede acceleration, resulting in increased fuel consumption. Ask anyone who's installed offroad bumpers lol.

Regarding derby and race cars, a weight limit can be in place for several reasons, such as fairness and safety.

 

I actually do know how gravity works, but thanks for the suggestion..... And im pretty sure they arent concerned w "driver safety" in pinewood derby cars, as they are about 8" long and are unmanned......NOT soapbox derby..pinewood derby.
http://en.wikipedia.org/wiki/Pinewood_derby

 

:facepalm: the acceleration of gravity is 9.8 m/s no matter how much you weight.

 

You have to remember that the tank has nothin to do with the fuel pump stopping. That is the filler neck, which is at most 2" in diameter. The point of stopping isnt gonna affect the amount of gas recieved all that much. A bigger affect would be the ground being unlevel. Thats why an average is good. If your averaging 14 and then average 20, you average is accounting for the same factors.

pinewood derby is different in that its only powered by gravity and ONLY downhill. Your fighting just as much force to go up hill as you are gaining going down hill.

And the force applied to the car is M*A=F, MASS x Acceleration = Force.

 

Yes but the person stating the heavier the vehicle, the faster downhill you go and thus save money but fails to realize it takes the same amount of work to get up the hill in the 1st place.

Has anyone noticed that mileage of vehicles really hasnt changed much since the 60's? expect for the advent of tiny econo cars with turbos but as motors become more efficient, safety regulations make the cars heavier and mileage hasnt improved much. Our new equinox with the 4cly gets the same mileage as our 73 buick limited with a v8, mid 20's.

 

I mention the part bout goin uphill as well.

You cant compare a car to a small SUV though. Look at the Corvette Z06, make 500hp and getting mid 20s MPG. If chevy made a Eco based LS it would hit 30mpg no problem, but V8s arent built for economy they are built for power. While economy hasnt increased much power and performance certainly has. I say performance cuz the smaller engines allow the cars to accelerate much faster.

Look at the new mustang V6, V8 power with 30+ MPG. Thats pretty damn good.

 

X2. My carborated 1964 Chevy Van get's about the same as my Jeep. Hybrid technology has been around for 100 years btw. Common in diesel locomotives to deliver goods, like gasoline to market more economically. Unfortunately any improvements in conventional engines seem to go right to horsies. Makes $ in the showroom I guess.

If we could get away from the idea everybody needs to drive a big heavy battering ram, to be safe from all the other battering rams, we could all be getting 50+ MPG in ultra light cars.

Of course it takes energy (fuel), to get all that weight moving, then it is transformed to air movement and heat in the brakes, since energy is never created or destroyed, it just changes forms.

I like "Distance= 32' x sec (squared)" Btw. IE....2 sec's=128 Feet (falling in a prefect vacuum)

 

lol...only in free fall dude, theres all sorts of friction to overcome first. there is always drag on the vehicle (air, rolling resistance). this is where terminal velocity comes in too...