I had a TERRIBLE tank going on the Insight over a span of 113 miles and found some cheap gas at Wal-Mart ($2.03 compared to the $2.29 next to my house). Since I had time I decided it would be a good time to retop the tank and try to startover again.

FCD read "55.something either 2 or 4". We'll say 55.4. Anyways, I topped off the tank. On the first click I stopped fueling instead of trying to get every drop of gas I can in the tank. Once I was done gassing, I had put 2.4 gallons in there! ---according to their pump--

Quickly I used my handy dandy calculator remote control watch to check my mileage. 45 miles per gallon! NO WAY! I starting looking all around the pump to see when the last calibration was done. While I was doing circles around the pump the girl came out of the cashiers cage and asked if I needed help. I said I was looking for the sticker to see when the last calibration was done on that pump as it was wrong. (or my FCD was wrong) So far the FCD has been incredibly accurate so the station had to of been off. She told me they were just calibrated last Friday so I took her word and left.

Any thoughts? Is this the latest WM rip off? Seldom do I buy gas from there,

 

The opposite may have happened on my last tank, which can only explain my last tank of 81MPG in my HCH.

My current tank is still about 2/3 full and crossed 450 miles. I'll have some adjusting to do with that last tank in the database.

 

I'm running the same as you with my HCH, abnormally high. Since my wife and I carpool in the Insight it doesn't get driven much and I haven't driven it during rush hours lately so I'm actually getting a decent tank for a change.

The Insight on the other hand gets better than HCH but not great for an Insight. New tires are in the near future. Someone put some cheap junkers on it (they have tread though so I'll limp them for a while).

 

I live in south Florida. According to our local paper, the Sun Sentinel, gas pumps here routinely fail periodic weight-and-measure tests. To do an inspection, the state inspector fills exactly 5.000 gallons (according to the pump) into a calibrated container, and then reads the actual gallons from the container. They are allowed 0.5% error. (Thats about 3 1/2 ounces per 5 gallons).

There are two problems: In more than one third of those tests, the pumps actually dispense less then the minimum required amount of fuel; and, in almost all cases, the state imposes no penalty on the gas station owner or operator. (And, on the rare occasion when a station owner is prosecuted, the charge is a misdemeanor, and the fine is small.)

The article doesn't say how much error is commonly found, only that errors exceeding 0.5% are found in more than one third of tests.

I do believe that at least two of the stations near my house routinely dispense significantly less fuel than the meter claims. This morning, a fill-up took nearly 14.5 gallons, according to the pump. Before that fill-up, the idiot light was not lit, I had nearly a quarter of a tank left on the gauge, and I had almost 50 miles remaining on the cruising range. When I calculated the MPG from that number of gallons, I got about 6 MPG less than I expected.

 

Keep in mind it is IMPOSSIBLE to fill your gas tank to the same level two times in a row. If you put in more gas than expected this time, you put in less than you thought last time.

Most ( if not all ) gas tanks have air in them. And depending on how much air escapes, or does not escape while fueling, you get vastly different amounts. In the case of the Ford Escape Hybrid, there is 3 gallons of air space in the tank. The tank is labeled as "15 gallons" but most people can never dispense that much. If you park on a slope, with the fill tube on the high side, you can ( and I have ) dispensed 17.5 gallons.

-John

Also keep in mind, nearly all MPG multi-functions displays on cars read HIGHER than real. This may be to make the driver ( who never checks at the pump... aka most people ) feel better about their car.

 

I'm curious if this is a common practice among owners, to try and squeeze every ounce into the tank.

When it clicks off, it's full, slipping a little more in can cause damage to the EVAP system due to fuel going into the lines and possibly damaging the purge valves and other items. This happens often on gas only cars. I'll see EVAP codes due to extreme over filling. Once the system lowers and fuel escapes from the EVAP lines the valves can again send and read vacuum, hopefully. If the fuel went to far some sensors could be fubared.

I'm not up to date on the EVAP systems for Hybrids so I wonder if similar problems could occur...

 

Fuel does expand and contract with temp. as well. When I would fill my Civic on a hot day in the summer the pump would click off noticeably early, and I could easily get another gallon in beofre the "actual" click off point. What time of day did you fill up at? I always do better at night or first thing in the morning. A HazMat tech at work told me gas can expand as much as 1/8 or more its volume depending on the temperature.

 

If that's true, then gas needs to be sold by weight, not volume.

How does $.50 per pound sound? ( there's 6.x pounds per gallon )

I'm sure it does expand, but 1/8 (12.5%) sounds ( a lot ) high.

 

A quick search and I found, in reality, thermal expansion is more like 1% from summer to winter. Here's why, the gas is stored underground. And winter or summer, the gas is always dispensed at between 60 and 65 degrees. Close to 60 winter, close to 65 summer. The pumps are calibrated to be accurate at 60 degrees, so you do get 1% less gasoline for your money in summer.

It does not matter what time of day you fill up, since it is the temperature in the underground tank, not the outside air that matters.

You should not "top off" in summer, because the gas will expand in your tank... after you already paid for it.... and could overflow if you don't use some right away.

Still, that 1% is extra profit for the gas station in summer.

 

Makes sense, since the tanks are underground. What about iN Canada, though, where many stations adjust the price of gas based on the temp (or so I've seen reference to)?