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When to fill up your gas

Randum

Go Kart Champion
So I always heard that letting your tank go to empty was not a good idea due to all the gunk thats found in gas- yesterday I overhear a guy talking about his buick, which has 390k miles on it. And attributes this logevity to the engine being well made, regular oil changes, BUT also said to ALWAYS fill your tank when its HALF full.

How valid is that? Half full is managible, but I usually "look" for a station when I hit a quarter left.

The old audi I had for well over 250k miles before that totally bit it, electrical system was its death, through high school I would run that near empty most of the time, filling it up with whatever change I found in the seats! lol

Any proof to filling it at half a tank? seems like overkill...
 

DvS21

Ready to race!
I like to keep gas in my tank just for the convenience. I think a lot of the "don't let your tank run down" is just 'wives tales' that may have had some basis in older (maybe even leaded?) gasoline. I usually won't drop below 1/3rd of a tank and do most of my fill ups at 1/2 anyway.
 

LittleJohny

Go Kart Champion
I never understood those who said letting the tank run empty is bad.

Isn't the fuel pumped from the bottom or near-bottom of the tank anyway? It's not like it's siphoned from the top down is it? So any gunk in the fuel would be teh first to get through the fuel lines anyway. But isn't that what your fuel filter is for?
 

edman62

Passed Driver's Ed
a gallon of gas weights approximately 6lbs, running your car with less gas in it has to result in more speed and better mpg. Maybe not a big difference but every little bit helps.
 

zee

Go Kart Champion
a gallon of gas weights approximately 6lbs, running your car with less gas in it has to result in more speed and better mpg. Maybe not a big difference but every little bit helps.

You are right based on what I have noticed. Fuel is too heavy to lug around.

I have been tracking my daily useage since I got the GTI. A little unscientific because my daily driving habbits cant be duplicated each day, but the route is mostly thesame and I noticed that...
-when I fill up half way to full, I got 9.5L/100kms. (24.76mpg)
-when I fill up empty to full, I got ~8.6L/100kms (27.35mpg), which shows that the bottom half of my tank averages ~7.5L/100kms (31.36mpg)

My log shows that I once filled up a 3/4 tank and averaged only about ~10.59L/100kms (22.21mpg):(

My average fillup is about 49L (12.94Gallons)
 

PandaGTI

Go Kart Champion
I've had a lot of my times when my cars would run until the estimated range was in the negative miles left... Never had issues wih longevity... 150,000 miles on my BMW and still running strong per the new owner, 190,000 miles on my Honda Accord before she was stolen, and 40,000 miles on my FJ with no issues.
 

Clempson13

Ready to race!
I usually fill up when i have <10 miles left on the indicator...probably should start once i hit quarter of a tank. that being said though...i believe the vehicle dynamics are tuned to the car having a full tank of gas and thus will provide a smoother feeling ride with the full intended weight of the vehicle. as bubuski has noted though...less weight in the car requires less power from the engine so your mileage will improve. overall though i don't think it is really detrimental to the life of the car where you fill at.
 

Carbon Steel

Go Kart Champion
This was discussed on another thread and has validity in aviation and i think it applies here as well. we always (if the gross wt. allows) top off our tanks, reduces the opportunity for condensation. fuel tankers and fuel storage tanks have filters that must be changed regularly (30 days log kept) as well, as the fuel must be circulated, water and contamination in fuel, will cause a reciprocating (spark plugs) engine to sputter and quit. some fuels have additives for anti icing and to eliminate bacteria from growing in the cells.

Another practical reason for me is that i have been thru a few fuel shortages, from power outages, storms etc. and if i have a full or nearly full fuel tank i am not impacted as badly.
 

Bender1

Banned
1) fuel pump lives in the TOP of the tank. it is cooled by gas. Once you get to about a 1/3rd (on most cars, dont know about ours) it is exposed and heats up limiting its life
2) gunk does float on top of the gas, the lower it gets the more gets sucked in. Fuel filter should catch most of it

I never drop below 1/4 tank and rarely drop below 1/3rd.
 

euphemus

New member
As Carbon Steel writes, there are a bunch of reasons to keep your tank full but I don't think 'gunk' in the bottom of the tank is one of them.

Personally, I prefer not to drive around with pounds of extra weight sloshing around so frequently run on fumes - wouldn't recommended that though :)
 

PENROSE

Go Kart Champion
I've been known to play "gas roulette"

I always try to see how many miles I can eek out of a tankfull.

My GTI (8,500 mi) just spent 3 days in my dealerships service department. 3 days ago my dash lit up like a Christmas tree with 3 CEL's. Car was sputtering so bad, I couldn't get it out of my driveway. Had to have it towed to dealer.

Just got it back today after they removed and replaced my injectors. They said they were all "carboned up"

After I got home, I noticed after I pulled in my garage that the car still has a slight "sputter/miss" while it idles while in PARK.

Back to the dealer it goes tomorrow.

Just food for thought, I guess.

No more gas roulette for me.
 

chinqutie

Go Kart Champion
i always fill up at half.. ;)
 

zeonic

mmm.... beer
i wait till the needle is on empty, then drive around some more until it dips below the last mark. i use chevron gas 99% of the time and throw in a fuel injector cleaner once in a while.
 
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