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.

1/4 tank fill up time agreed!

Just my personal experience: '94 F150, bought new, dual tanks, both with electric fuel pumps.

More often than not, I run a tank until she starts to buck from fuel starvation, then switch tanks.

2012 - 1994 = 18 years of doing that with no fuel system issues whatsoever.

To OP: Run it down to under 1/4 tank before filling up, and halve the number of fuel and time wasting trips to the gas station vs. piddling around with partial tank fills.

Run them as close to empty as you dare once and a while, best way to avoid water build up, is to not let it get started.

I used to do that too with my '95, never had any problems. I really loved that truck, I thought 18mpg city was pretty decent.

Was yours the 300 i6?

Still is the 5.0 E4OD 4x4

I run until empty and neutral coast to the nearest gas station.

Otherwise, I let it run down to the last 1 to 2 gallons (14 gallon tank) and then fill completely.

Suuuuure ya do.

While I have done it, I don't make a habit of it.

One time a bunch of us were out motorcycling and one guy's bike sputtered out of fuel. While still rolling down the road, I told him to put his passenger footpeg down. I pulled alongside and pushed his bike that way until the next gas station- thankfully, it was real close. My right leg felt like it was about twice the size of my left for a while after that.

You sure that was your right leg?

There was a shoe on the end of it, so I think it was... :confused:

One of the nice things about getting accurate consumption numbers and knowing exactly how far you can make it on a given amount of fuel lets one run down pretty low and still be comfortable with the quantity left in the tank.

That said the civic has a hesitation right after bump starting when the tank gets quite low. Once that happens it is time to refuel.

ok folks, i'll give 1/4 tank a try!:thumbup:

I have 13.4 gallon tank, and I always fill all the way up and wait until I get the empty light before refilling.

Ideally though, the less weight you drive with the better. Some people even mod their cars to have a smaller tank, so they forcibly run with less weight on a full tank.

I say, just fill 'er up, and unless you're willing to go to extremes, don't worry about it beyond that. You need to use a full tank every time you fill up to accurately and easily calibrate your Scangauge, anyway.

Once you get to a point where you're getting twice as much MPG as stock, then you can start half-filling and maybe thinking about getting a half tank or something.

If I had a garage and was getting really bored, I might consider syphoning my excess gas into a 50-gal drum but until then...

To each his own, but I run mine down to almost completely empty. This is for three reasons.

1) More accurate mpg numbers
2) It's a game with myself to see how many miles I can get out of a tank
3) I have a tank that nominally holds 34 gallons. The grocery store I use (Kroger) gives me a discount on one fill up per month up to 35 gallons. If I run till empty I can go all month on one tank and 35 gallons fills me up into the filler neck. In the last 7 months I've driven 7,853 miles on 7 tanks.

I've never run the truck out of fuel, although once I had it in the shop and they ran it out while test driving it. That's not something I care to repeat--every so often some air would hit the injectors and it would stumble & studder. It took a week or two for the intermittent symptoms to go away.

...let me "back-pedal" here for a moment and say that I agree 100% with #1 above...especially when attempting to "calibrate" my SGII for the first time. However, once I have things "dialed-in" I revert to 1/4-tank threshhold:

1) to eliminate "running OUT of gas" anxiety.
2) ensure the wife won't run it "empty" accidentally.
3) guarantee the in-tank fuel pump is NEVER exposed.

...hence, almost ALL my fill-ups measure around 300 miles, because typically I can easily get 100-miles per 'each' 1/4-tank mark on the gas gauge. However, on LONG trips, it's 400 miles between fill-ups, because of the better highway MPG's.

...here in Tucson, it's FRY's, instead of Kroger's, but same "food-for-gas" scheme.

Never thought of it that way. Sort of like the corrupt oil-for-food program with Sadaam Hussein. :D

As far as the accuracy goes, I know it is better to do it in 35-gallon increments. The thing is, it takes me 3 months to do an A-B-A test with hand-calculated mileage. That introduces other sources of variation (weather, etc.).

When it drops below half-tank is my preference. Usual range is above 700-miles per tank town or country. But having lived in tornado & hurricane country all my life has sensitized me to being low on fuel, ever, as being a mistaken habit.

There are days and drives I don't care to have to think about where to buy fuel (additive quality & freshness), and, as I try to combine trips, my choices when around town are such that I prefer the luxury of fueling when and where I choose. Thus to fuel is as much an errand as any other, and deserves being included with other stops. Rather, other stops may remind me that I'll passing by a favored fuel location, thus -- if under half -- an easy time to keep the tank topped off.

.

Recnetly with the rising gas prices, I have used my 3@5 gallon fuel cans to stock up on fuel. Last stop it was $95.15. 15.8 gallons in the car and 10 gallons in my extra tanks.
That gives me a 15 gallon inventory above the full tank in the car. In the 2011 CBR that 15 gallons at 75 MPG, gives me a combined range of right at 1575 miles. That depends on the weather, since I avoid riding the bike in the rain.

Here we also have to deal with hurricanes and potential power outages that can last as long as a week, even closing the gas stations unless they have auxiliary power.

I try to fill the cans with precisely 5 gallons each so I can still keep track of my mileage, and when I post to my garage I will break the total consumed into two separate fills to keep my average tank miles close to correct.

regards
Mech

It seems strange to me that no one has mentioned that CRUD could be at the bottom of the tank, which we don't want clogging the pick up.



Never had a problem w Japanese motorcycles on switching from main to reserve,
but on a past Harley; huge pain of kicking, and kicking, and kicking! Sweaty!

new (low miles) '75 FX 1200 Superglide.

I was just picturing Frank getting a green stick fracture to his leg, had his friend
needed to lock up the brakes for a dog or something.

PS. I love the idea of that perfect long tank mpg figure, but crud potential would always be in the back of my mind.

...with todays electric fuel pumps being physically located in the very bottom of the tank, crud is there, around the pump, ALL the time (albeit in differing proportions) whether the tank is full or empty.

Also, many modern tanks (including mine) are now plastic rather than metal. While it doesn't eliminate the crud it does reduce it as much of the crud is rust flakes coming off the inside of the tank over time.

If crud is getting sucked in (as well as water from condensation) it is an issue that should be addressed, regardless of how empty a tank is getting.

With gas prices still rising do you guys still suggest running it to empty-1/4 tank?

i drove past the gas station and it was a 3.0x, i only used about a quarter tank at this point. I come back the next week or the one after and it was now 3.2x or 3.3x

If your gas prices vary by 30 cents it might be a good idea to get gas earlier, when it's cheap. However I really don't pay attention to prices because they usually don't vary much from place to place.

I always run it down to the end, and in my Rabbit I've gone down to the last 30 miles or so. That was nerve wracking but incredibly exciting! It was also a big rush to get over 500 miles in the Probe. I see no reason to fill up at 1/4 tank if you have 100 miles left to drive. (My dad keeps a 5 gal tank in the barn for power equipment, regardless. Good for 70-200 miles depending on what I drive)

The red "empty" line is usually not the end, either. Automakers give you a little leeway.

Apparently the Probe tank is 16 gallons. I've never used more than 12 gallons (the 500 mile tank- into the red) so you can see how much room they give you to drive farther. I could have gone 650+ miles at 42mpg.

I do recommend running tanks near empty regardless of what prices are doing. Fuel expenditures average out over time whether you make many small purchases, or less frequent full tank fills.

By making less frequent stops at the station, you spend less time at the pump and waste less fuel driving to the station and waiting in long lines for a pump to become available.

However, I am considering a bulk diesel purchase before those prices spike too high. I can store about 500 gallons at my parents house.

...drive as long/far as possible on the lower-cost gasoline you already have, instead of running out and filling-up so you can immediately begin burning-through (pun intended) the higher-cost gasoline.

When I fill is situational. I like to fill before long trips even if is only a couple of gallons, just part of my ritual like checking the oil and tire pressure. Also on long trips if I'm stopping for some other reason I may fill the tank if it is below half. A few years back on the way to see my son, he said if I get to a certain town and its after 10PM Sunday and need gas, fill there because you won't find open the rest of the way. Hurricane in the forecast fill and fill early. The last fill there was only about 1.2 gallon left. So like I said it varies.

But the one thing I do is fill the tank.

Lost probably 14 gallons today when I sold the Maxima, but at least the fine gent who gave me $3300 cash for the car is now getting twice the mileage of his V8 4dr Tundra at 15.9 MPG for the 90,000 miles he has commuted in the last 3 years. That's close to 6000 gallons of gas!

regards
Mech

...so, selling cars is NOT really like stock brokering., ie: "...sell LOW, buy HIGH (gasoline in the tank)..." (ha,ha)?!?

I'm told the fuel is what cools the in-tank pump - so I don't usually drive till the yellow light comes on or till the needle gets down by the lowest gauge line. If my pump will last longer due to running cooler, that's worth a few extra minutes of my time now and then. My two cents.

I would assume that the fuel running through the pump would provide at least some cooling, and unless your fuel pump is running at a high amperage rate, I can't imagine that much heat being generated.