I Stretched My Bladder!! (i think)

i went to the gas station today filled with anticipation since my computer mileage was at 56.5 mpg. i figured for sure that this would be the 3rd consecutive tank in a row with increased mpg.

but the "pump" mileage worked out to only 52.2 mpg!!! that is 4.2 mpg below the computer. i was astounded.

so i started to think why this had happened. i think that i basically have filled up to a fuller tank than i have before. the reason i think this is that i was unfortunate enough to choose a pump that had a messed up seal on it. so when i filled up, it pumped only the first 2 gallons or so in and then it kept shutting off. i could then only put gas in in 10-20 cent increments. ( a major pain in the A#@!!) this made it difficult to determine where full was since i couldnt even keep the pump going at the lowest speed either.

i stopped at the nearest dollar after i got to the point where i could only put in a nickel or so at a time. so i guess, im going to have to wait until i fill up again to really figure out where my mileage stands.

but the pump mileage is only .7 mpg below my lifetime average. but it does make the lifetime difference from the computer verses pump average to 1.5 mpg. because of lower gas prices ($1.839) i set record for lowest cost at 3.34 cpm

but i was surprized at how difficult it was to put gas in when the seal was screwed up. no matter how hard i pushed the nozzle in, it didnt do any good. this is also the first time i actually could smell gas when fueling my Prius. so i guess i poluted even though i didnt spill anything... :|

 

well i have seen two kinds of gaskets. there is the flexible hose that is large enough to cover the entire filler tube.

unfortunately, the one i had problems with is the thicker donut shaped one that seems to be filled with soft foam. it is the same size as the outside and can be difficult to seal well. the one i had the donut was crushed on one side and torn away from the nozzle a bit.

as far as capacity, i dont run the tank that low to be honest with ya. the most ive gotten on a tank was 470 miles but i had 2 bars left. (ive never seen it down to one bar)

but as i said, i'll just have to see how the next tank looks to get a good idea of things. when doing the fill the tank up even in a regular car, you will have variances that will fluctuate your mileage a ½ mpg or so. i really only look at tankfulls to see if any trends are developing. the only thing i really take to heart is the lifetime mileage. (the more gallons and miles you add up, the smaller the error in your calculations become)

 

ok i have an update.

it now appears that my bladder did not stretch. i simply used a gas pump that ripped me off.

i have come to rely on the mpg reading on the computer more than the "pump" mpg simply because its an established fact that 11% of pumps in WA st are inaccurate. (the nationwide average is expected to be about the same as the inaccuracies is the result of physical deterioration of a metering value in the gas pump. the only way to avoid this possibility is to only use pumps that have been inspected recently. that is something that i am beginning to find out is not possible where i live.)

i was going to use the same pump 3 times in a row to eliminate variations in fill amounts, but after two times in a row where the pump average was way below the computer average i decided i was tired of giving away my money.

i have since reported the pump to the dept of weights and measures and they said it will be put on their inspection schedule. a quick survey of the other pumps (this is a big station!) shows that 7 pumps no longer have the inspection sticker ( a violation of the law) and others have inspection dates that range from May 1999 to April 2000) ironically, this station is located about 3 miles from the state weights and measures office. the station is off Lakewood Dr in Olympia WA. (its the Arco station that you would see just off Hwy 101 at the Thurston County Courthouse exit)

 

if there were any repairs made on the pump, then the inspection sticker should have been updated.

if they were inspected less than 2 years ago, then they most likely were inspected because someone complained about the accuracy.

im still waiting on my inspection request. i am positive the pump is off though. i figured that using those pumps lowered my overall mpg .6 mpg

BUMMER!!

 

well actually, im comparing the accuracy of the computer and the what is figured mpg using the gas pump figures.

i am beginning to think that the computer is the most accurate measure and that variances are not due as much to bladder volume differences than the differences in the gas pumps.

the reason why i felt this way was because, i was religiously alternating between the computer being over and being under the pump mpg's. this is attributable to the variances in the volume of the individual fillup.

but then, i changed stations that i normally used and experience two tanks in a row that were below the computer mileage by quite a bit. (3.2 mpg and 3.8 mpg. up until this time, i was less than a mile apart from lifetime computer verses pump mpg.)

right away, i suspected something fishy. when i got a third tank that was under the computer mpg then i was convinced my theory was correct.

i am now waiting for positive confirmation from the state on my findings.

 

well good question, at least that is what i thought when i first got my Prius. and i did add the pump mpg's so my spreadsheet didnt look so anemic to be honest with ya.

but serendipity has struck again. i have begun to realize that i can use the computer to gauge how accurate the pump is. i quickly noticed a pattern when using a certain pump that im positive is shorting me at the pump. the reason was 3 consecutative tanks when the pump was lower than the computer. something that has never happened before.

previously, i alternated between being over and under the computer reading. remove the times i used the suspected short pump and the difference bet pump and computer is .8 mpg. now realize that i have had tanks that were as much at +3.4 to -2.8 mpg. but that is due to variances in tank fill levels.

but getting short or over 3 times in a row means that a measurement is off. so the possible culprits are the computer being in error or the pump in error (assuming you dont spill any gas, etc) seeing as it has been shown in a study performed by KING % news this past spring that 11% of the pumps in the state are inaccurate, i have to blame the pump.

to further test my theory, i went to where i was getting the best mpgs (yes i tracked location and pump # too...so more of that macho spreadsheet thing :roll: ) and i now im sure of my findings. i will have fairly definitive proof Fri Afternoon when i gas up. that will make 3 tanks at the suspected worst pump and 3 at the best pump.