when to fill up?
 

Hi all. My tank holds about 70 ltrs, but I usually fill it up when i've done 200-250 miles (about 1/2 tank). ie its usually topped up. What do you guys do. Is it better to
a) stay as I am
b) use it all up, say 65 ltrs, as a constant full tank is excess weight , then fill up again,
c) only fill it up to 1/2 tank, then use that, then another 1/2 tank, as the weight of say 35 ltrs of dino is not insignificant. Down side you cant check mpg between tanks.

One liter of water weights almost exactly 1kg, and while 70 kilos isn't negligible, I'd say it's not terribly significant in a car the size of yours. You could probably net slightly better city numbers doing the half tank thing... but I fill mine all the way up for convenience's sake.

I always wait until I'm near empty before filling. No use in driving around with extra weight. Filling to a half tank isn't worth it and makes accurately tracking mpg impossible.

I generally run my 18+ gallons tank down to the point where it takes 15-16 gallons to fill.
Any lower and you may cavitate the fuel pump if it is an in tank type. Since the fuel also acts as coolant for the pump running it to empty can cause premature fuel pump failure.

I may fill earlier if I take a road trip and want to get back on the same tank of fuel since it is generally less expensive here. Anything below 500 miles round trip and I can make it on one tank.

regards
Mech

I run down to between an 1/8th of a tank and the low fuel light. Generally around 11 gallons in a 13.7 gallon tank on my car. The only time I fill up when the tank is above that would be when finding gas significantly cheaper than what I usually pay.

I fill up whenever the car/truck is below 1/4 tank and I've checked gasbuddy.com for the cheapest on my route. Unless we're on a long single day drive down the interstate, then I'll let it get to nearer to 1/4 remaining.

Sure you'll get fractionally better mpg around town but I think the benefits of keeping the tank nearly full outweigh the cost. in no particular order: 1. 9/11 ring a bell? 2. less condensation space in the tank. 3. If your really low you might need to get gas in a less than desirable location.
Ed:turtle:

the two-sides of this operating "coin":

1) driving until almost empty means you're spending half your driving time lugging less fuel around...

while...

2) filling-up before half-tank means you're spending almost all your time lugging an almost full tank of fuel around.

Time is money. I want to spend as little time at the pump as possible, so I fill up and run the tank down to the last 2 gallons. I've yet to run my TSX out completely.

I fill mine when 1/4 tank left.

...same here, I "split-the-difference" between 1/2 and empty, which is 1/4 tank.