Gas tank size

[Peakster]

My owner's manual says that my gas tank holds 10.6 gallons, but I managed to squeeze 10.9 gallons in the tank from a complete empty right to the filler edge. There's no 'fuel low' light on my car, but the needle was pointing right at the top of the letter 'E' on the gas gauge when the engine started sputtering:

Attachment 317

[zpiloto]

Originally Posted by Peakster

My owner's manual says that my gas tank holds 10 gallons, but I managed to squeeze 10.9 gallons in the tank from a complete empty right to the filler edge. There's no 'fuel low' light on my car, but the needle was pointing right at the top of the letter 'E' on the gas gauge when the engine started sputtering:

Attachment 317

Thanks. If anyone else has run out of gas and filled let me know what the discrepancy between owners manual gallon amount and actual fill was.

[GasSavers_Brock]

I would say every manufacture is different. The 99-03 TDI's are suppose to ahve a 14 gallon tank but I have put 16.2 in when I was running on fumes...

[cems70]

"huh ???? you put 15 gallons in a 10 gallon tank?"

"He didn't say he put in 15 gallons, he said he put in 5 more after the pump shut itself off."

Both of you are right. I was able to regularly trickle in 5 gallons more after the pump shut itself off. Sometimes the car was completely or almost completely empty (i.e. the pump stopped at 9.8, 9.9 or 10.0 gals) and I could still squeeze another 5 gals in if the pump was sensitive enough to let me trickle it in. And the extra 5 gals really was in there because I got 250+ more miles from the that tankful of gas (regardless of where the pump stopped, as long as I put in an extra 5 gals). One of the inexplicable wonders of the '92 - '95 Civic VX hatchback...perhaps also w/ the DX hatchback as I'll be trying the same with said car on my next tankful.

Steve

[Lug_Nut]

My 97 VW Passat wagon has a published capacity of 18.5 gallons (70 liters). I have pumped in 28.5 gallons after having driven to the station.
The 95~97 Passat sedan has the same published fuel tank capacity, but has an entirely different fuel tank. The most I was ever able to add (without having run dry) to the two of those I owned was about 24 gallons.
Neither the sedan nor the wagon has no low fuel warning. But at 50 mpg, "E" doesn't mean 'empty, it means 'enough'.

[JanGeo]

I am surprised at the ability at add that much more gas and then be able to use it. Once the pump I was using sucked the gasoline back in with the vacuum sensing cut off system so each time I clicked in some gas it sucked it back out. But the only way I think you could get 5 more gallons into a tank is if the tank had a blatter that expanded (prius) or there was a misprint in the owners manuel listing the capacity. You could be getting a pump error and we all know that has happened at gas stations or maybe if your car has a really big charcoal canister that can hold a few gallons and it gets filled . . . Only thing else I could think of is the tank bottom or sides bend giving it more capacity when filled - there is some small amount of pressure from filling the neck to the top. My Geo used to run rough when it got low and the needle would stop moving when going up and down hills - the rough running was caused by air pumping in the gas line - I actually ran it low then pumped the rest with the fuel pump out into a gas can to see how much was left. Stopping at the first click depends upon the gas foaming properties and the flow down the filler pipe and the bend in the nozzle into the filler pipe. The gas comes out of the nozzle really fast and it splashing back up is a factor of a lot of things including anti-blowback flaps in the filler pipe. Diesel filling stations for boating even have high speed hoses that pump something like 50 gallons a minute which you need when filling 1000 gallon tanks!

[diamondlarry]

Originally Posted by theclencher

Not only is every manufacturer different, every model and perhaps every car is different. This may sound stupid but I do it because I want to know: when I get a new-to-me vehicle I put a gas can with gas in the trunk and run 'er 'til she quits. Then I know what the gas gauge readings really mean! For example, the old Tempo will go quite a long way past "E" before it runs out while on the newer Tempo, the instant the needle hits "E", you're done and you're walking. Every vehicle I have has been different in this respect, sometimes by a large margin. Also, by running it dry then adding a known quantity from the gas can, then filling up at a station, I know the true capacity of the system.

Now that is all on the "bottom end" of the range. The correlation at the top end varies too- on some the needle doesn't go much past "F" when "full" and on some it does. Evidently consistency and accuracy in fuel gauges is not a top manufacturer priority.

That said, I'm somewhat mystified by the whole topic of how much more can be forced in anyway. I suppose cramming a few more gallons in could be good in that it can reduce time, mileage, and potential spillage and evaporation losses from extra gas station stops somewhat- quite the opposite of the guys that like to run to stations constantly and top off or only run on a couple gallons at a time. Lug Nut: 10 gallons extra?!? Sounds like a misprint somewhere along the line...

I guess I've had enough experiences with "old school" equipment to discourage "over" filling past the second or third click. The worst one was when the Coop fuel guy overfilled Pa's fuel barrel back on the farm; it was a hot day and the doofus filled the hot outside tank (with cool fuel from an underground tank) right to the brim. Shortly after he left I noticed fuel streaming out the fill cap and down the sides and the worst part was, everything on the place was full already; there was nothing I could pump any gas into to relieve the expansion. Horrible, horrible waste. Scarred me to this day. Also happens with old vehicles and equipment w/o evaporative control systems: fill too full when it's cool (best time for filling) and then it goes out the vent or the filler cap and onto the ground during the heat of day. Trauma! And like psy, I've had the old Chevys with the early evap systems puke fuel too. It's even the same way with little stuff like lawn mowers- the vent caps aren't all that sophisticated, it's just a series of little baffles in there and if the tank is too full the heat and vibration of operation will send all the extra right out the vent.

In sum, overfilling seems a pretty pointless exercise to me. I just go second or third click at the pump, or nearly but not to the brim when using a gas can on small engines. Losing gas to spillage or evaporation is not a gain.

I usually do the same thing as you do when I get a new-to-me vehicle. I haven't done it on my current car though. As far as overfilling/filling to the brim, I live far enough away from the station that the trip home usually creates enough room to take care of expansion. I too learned the hard way about expansion at one of my old jobs. I was the delivery driver and I filled up one Friday in the winter right at the end of the day and brought the truck back and parked it in the building. Since the station was only ~1/2 mile away, on Monday morning there was quite a mess on the floor. I strted filling up earlier in the day after that.

[GasSavers_Brock]

On our gasser I very rarely "top it off" because unless you’re going to drive it a distance right away it might expand and leak out.

For those of us with diesel the expansion rate is much less. I top off every time and have never had any issues. Even filling and then letting it sit in summer. Diesel just doesn't expand as much.

[CO ZX2]

For quite a while during the time we've owned the ZX2 I filled it quite often by continually clicking the nozzle till fuel ran out the filler neck. I thought that was the only way to know I had a full tank. I think I did have a chock-full tank but that was causing a problem in itself. Occasionally the car would run badly for a few seconds while driving, took me a long time to wise up to what was happening.

I have a CD of workshop manual information and the tank drawing shows considerable space in the tank intended for fumes and expansion. The info also speaks of overfilling and the likelihood of actually having liquid fuel migrate to the charcoal canister. When the evap system purges it dumps the vapors and liquid, if present, into the engine. This fuel is not metered, just dumped. I believe this is exactly what was happening to my car. I finally read the owner's manual and it cautioned against overfilling and recommended a max of 3 clicks beyond auto shutoff of pump. I have used 1 click beyond auto shutoff for over 7000 miles without deviating. Most of my fills have been at the same pump/same station. Remembering from previous fills, I could probably say I could force another 1 1/2-2 gallons in with multiple clicks.

Especially after I got on the serious gas mileage kick I became so exasperated with trying to get consistent fills, I felt I had to do something different. This led me to ScanGauge. ScanGauge picks up the injector pulse width and count from the ECU and uses this info to compute the amount of fuel the engine uses.

After the miles I have travelled with SG, I am totally confident it gives a far more accurate measure of fuel used. No way would I ever dismiss SG fuel-used figures in favor of pump readings. I have been dead on with SG a number of times with gallons pumped and within 1% for the rest. Any one of these times I could have forced more fuel into the tank, declared SG wrong and done my own calculations for a better FE figure. I will not do that. If I had no more faith than that in the accuracy of SG, I would not even use one. I do not correct any fills considering the accuracy I know I have. I believe interjecting my own figures into SG to get it to match the pump would cause me the same difficulty and uncertainty with SG I see so many others having.

Since I started using 1 extra click filling, the occasional rough engine I mentioned earlier has never happened again. My mileage also picked up at that time. SG changed my driving drastically which accounts for a lot of that. But I am sure the overfilling I had been doing was wasting gas thru the evap system.

[LxMike]

CO, do you wait for the low fuel light to come on or what set point do you refuel? according to the manual our cars have a 12.8 gallon tank. i've never got more than mid 9 galon in when the light would come on.

I might have to do what clencher does and find out what it takes from dead empty.