Inaccurate Gas Pump?
 

I filled up Slambo after 195 miles of clean driving yesterday (knock wood, she's been running really well, the weather's been perfect, and the roads were clear). The fuel gauge was in the 3/4 range. I expected a meager 4.3 gallon fill (or thereabouts), based on careful instrumented driving.

The attendant (hey, it's jersey) pumped in 6.891 gallons. :eek:

This was my normal station (of late), but a different pump and grade (switching from regular to premium).

The '99 Civic HX has a 11.9 gallon tank.

Where did the extra 2.5+ gallons go?

Could the pump be that wildly miscalibrated?

Note: I usually wait until below half full to refuel, but I wanted to have a full tank from my normal station before taking a trip up north this week.

Best guess would be you filled before at the same pump then changed pumps and got the greater than expected fill.

If so then refill at the prior pump at the same point on the gas guage. If it stops at the amount you had expected, as it had done before, then pull over to the premium pump and see if you can get 2+ more gallons.

Your rear end was lower than the front one the earlier fills, not so at the premium pump.

Try it and see what happens.

regards
mech

Most states have people who drive around unannounced to gas stations and buy exactly 5 gallons of gas, in a container precisely capable of measuring 5 gallons within 99.99 percent accuracy.

If the stations pumps are off by any decent amount they close them down and they could be liable in a class action suit in some states.

regards
mech

Thanks for the suggestion, Mech! I've never seen anything this extreme before.

I'll go back to the first pump on the next visit. Both are on the same side of the island. From memory, it's level, but I'll give it a good look. Perhaps the tires were off the concrete pad on one side or the other …

Ah, the Silver Lining! This might be the opportunity/excuse to shoot a video segment on the Bureau of Weights and Measures.

Gas tanks under the rear seat are not very "tall' at all. With a filler neck 3 feet long and not coming in at the very top of the tank, the level of the car is critical.

Watch your gauge and see how many miles you go to that exact same level you mentioned in you original post. If my ASSumption is correct then you should have traveled considerably further if your fill was more complete.

If that is the case, get a foot long 2x4 and drive the wheel closest to the filler neck on the board to gain some elevation on that corner of the car. Fills should be come much more consistent.

And all that advice did na cost ye a dime LOL.

regards
mech

The wife's Murano would auto shut off the pump, but I could easily trickle another 2.5 gallons in the tank, listening to the gurgling noise until it got to the filler neck. Never go to the top of the filler neck or you could saturate the charcoal in your vapor recovery tank. For that reason, I just fill until the pumps auto stop on slow speed and leave it at that.

Are Jersey gas pumps still attendant only?

regards
mech

this is possibly why or at least contributing. fuel gauges are not always linear, though certain vehicles are far worse offenders than others. every GM vehicle I've been in likes to hang onto Full for nearly 4 gallons of usage, then drops fairly rapidly down towards empty, then when on empty, there can be anywhere between none and ~2.5 gallons of fuel in the tank.

it's kind of dumb, but it works well enough.

More great stuff!

I'm looking for my highest tank MPG ever, if the amount pumped yesterday was true (allowing for an ultra-full tank) and driving conditions permit. The variables are infinite … only time averages them out …

Aye, yup! Contributing, I'd buy. But the discrepancy is crazy big.

I test a different vehicle every week. Not sure if any of them are linear. It's always fun to watch the Distance to Empty numbers changed based on driving style.

Yerp! Still attendant only. Some of the cheapest gasoline in the USA (tax per gallon is low) and we don't have to get out of the car when the weather's nasty. They tax the daylights out of us on everything else.

Jersey Girls Don't Pump Gas. :thumbup:

Of course .. sometimes the pump is way off and some states are not as big on enforcement .. some states don't allow liability to attach .. and some states even have a maximum $ fine per year .. once a pump owner knows they've reached the maximum , they are immune to any further fine , no matter how off pumps are for the rest of that year ... etc.

For example:

Link

Only getting around to check each pump once every 3 years .. and than finding for example 6 pumps off by up to 200 cubic inches out of 231 cubic inch test .. = .. an ~86% pumping error .. and that ~86% error pump got between $300 to $500 fine ... I think the gas station made out more $ over that 3 years than the cost of the fine.

From 2007 to 2008 Arizona only issued citations if the pump was off by 6 cubic inches out of 231 .. = roughly a ~2.59% error rate ... If it was only ~2.58% error = no fine = keep on pumping less gasoline than you charge the customer for.

UPDATE: 200 miles and the needle is just starting to fall below Full. I reckon you're spot on Mech!

Back to the original pump (after another 200 miles or so).

I always go to the same pump at the same place facing the same direction with the car in the same spot. This reduces variability:thumbup:

Yep! That is my usual modus operandi, although I switch from brand-to-brand, I run as many fills in one spot as possible. I've never seen such a huge variation. Big lesson, I learned. :thumbup:

Yep! I learned very early in my Ecomodding newbness that the slope at the gas pump has huge effects on filling. On my 3rd or 4th tank ever recorded, I was screwed out of a 44+ mpg fill due to going somewhere else! I got a measly 42.

It made your next tank look pretty good, though. ;)

THAT is true :D

The cheapest station in this area is a major chain, but always cheats enough to notice. I decided it is not worth the few cents per gallon.
The one place that never pumps more than my tanks are factory rated to hold is owned and managed by an old guy who attends the same church I do. So if he's a couple cents per gallon more, fine by me.
When I travel, I only buy from big chain truckstops on the outskirts of major cities, just off the main interstates. Never pumped more than the tanks' ratings at any of them, that I can recall.

Slambo's next tank is gunna be huge … :D

Don't forget to calculate the amount MMO you add as being gas... otherwise your tank is going to look even better! :D

I only fill at stations less than 5 years old, Texas soil expands and contracts and can damage the large I'm ground tanks. It's the main reason homes down here don't have basements and roads can only be paved with concrete.

it will be interesting to see if the premium fuel and mmo improved your effeciency. I can not comment on why the fuel additive helps on Hondas but just for kicks I added about an ounce to my lawn mower fuel. I could hear the idle change after the mower worked it's way though the feed line. Seemed to increase rpms without increasing or decreasing choke

The numbers are in:

Overfilled tank produced 28.34 mpg (lowest tank ever), followed by 63.27 mpg (highest tank ever) back at the normal pump.

When that happens to me, I move a gallon or 2 back to the other tank so I don't have a false best tank.

I remember once when I was filling up my Polo that I saw almost 60 litres of petrol at the pump, I had fuel for at least 100km of driving and my Polo has 50 litres tank ;-)

That's the sad reality here in Poland sometimes...