Vexed at the pump

[grggwlkr]

In Kentucky, you pump your own. I try to be consistent, first click on the nozzle and stop when it clicks off. No top offs.  Anyway, my previous fill up filled me with joy as I looked at Fuelly and saw 49.9mpg for the fill. Now to yesterday's fill up. The trip 1 was showing 11 gallons used but my low fuel warning had come on. I had 530 miles on the tank and avg MPG of 51.1. Something is not adding up. Roughly 50 mile drive home from work and the warning turns red and miles to empty read 30. What the hell, I should have nearly 2 more gallons in the tank. I I get to the gas station and fill up and put 13 gallons in using the same method as always.  Trip 1 said I had used 11.48 and I put in 13.04. Fuelly says 45.3mpg when trip 1 says 51.1. All I can figure is my last fill must have clicked off 1.5 to 2 gallons too soon.

 

Moral of the story is when to red low fuel indicator comes on,  TRUST IT!

[wab]

YEP every handle will click off at a different level AND that level will change as the handle wears.

 

I've thought about pumping what the car says I used.

BUT IT IS A DOCUMENTED FACT that the pump always lies

IN FAVOR of the station.

[KCmax]

In Oregon, we're one of only 2 states (I think) where it's illegal to pump your own. A few weeks ago after a fill up I entered the numbers into Fuelly and was amazed that my mileage had suddenly leaped up more that 10 MPG! It had to be too good to be true, and as I drove away I realized that the attendant had not topped up the tank. I thought about going back to complete the fill up, but that would have made me late for work.

It totally screwed up my Fuelly statistics, GRRR! I suppose in the long run it will be a blip, but I don't have that many fuel ups yet, so it was a bit frustrating.

Edited September 3, 2013 by KCmax

[ScubaDadMiami]

IT IS A DOCUMENTED FACT that the pump always lies

IN FAVOR of the station.

This is why I decided to go with what the C-MAX says, not what the pump says. It is consistent.

[RaPieR]

I drive a pretty regular route and fill-up at the same pump in the morning every week or two.  Doing this has led to a pretty consistent reading between calculated gallons used and actual gallons used.

 

Date - Actual / Computer Calculated

9/3 - 12.94 / 12.68

8/30 - 1.81 / 1.78

8/27 - 15.24 / 14.61 (Used a different pump for a partial fill-up in Canada)

8/19 - 11.94 / 11.89

8/15 - 2.42 / 2.41

8/12 - 11.89 / 11.69

8/9 - 3.76 / 3.68

8/3 - 3 / 2.85

 

The results have been pretty consistent especially after the PCM update.  Before I would get slightly higher error in highway driving and low error in city driving.

[Noah Harbinger]

I'd say don't go back to that station. I find the stations around here generally short about 2%. 2 gallons out of 13 is 15% - that's way too much!

 

By the way, LOVE the car name :)

[C-MaxSea]

This thread has prompted me to revisit one of my fill-ups.  RaPieR, yours look pretty consistent - mine are as well, with the dash always lower than the pump.  I had one that I felt was bogus, however, where the dash showed 12.56, and the fill-up showed 13.36.  It was at a gas station 'on the road', and it did not seem correct.  It does seem to matter where you fill-up, and how careful you are (flat surface...).  I may go back and 'split the difference' on that one.  Nick

Edited September 4, 2013 by C-MaxSea

[tehuti]

How accurate is the "Miles to E" calculation anyway? Typically I fill up with a quarter tank to go, but with all of the talk on this forum it sounds like folks are milking the tanks a little closer to E than I am comfortable with. Today I supposedly have 62 miles to E and my commute home is 30 miles. That would be perfect for me to fill up at my usual station near home tonight. However, I am uneasy when I see the yellow pump icon, even though I should have plenty of gas to get me home.

 

Any comments? Am I taking a risk or do I have nothing to worry about? BTW, it's probably going to be close to 100 degrees out today.

[moytoyx]

In Oregon, we're one of only 2 states (I think) where it's illegal to pump your own. A few weeks ago after a fill up I entered the numbers into Fuelly and was amazed that my mileage had suddenly leaped up more that 10 MPG! It had to be too good to be true, and as I drove away I realized that the attendant had not topped up the tank. I thought about going back to complete the fill up, but that would have made me late for work.

It totally screwed up my Fuelly statistics, GRRR! I suppose in the long run it will be a blip, but I don't have that many fuel ups yet, so it was a bit frustrating.

Jersey being the other one.  I just mark my fillup on fuelly as a partial - and then hope it is done correctly the next fill-up.

[fbov]

How accurate is the "Miles to E" calculation anyway? ...I am uneasy when I see the yellow pump icon, even though I should have plenty of gas to get me home.

I find MTE a bit capricious as it seems to have a very short memory. One might think it would use the lifetime average MPG, but it seems to be adaptive, showing greater range when the car's being driven more efficiently. As long as you drive consistently, and don't decide to hot-rod it home, you should be fine. If you just came down from the mountains, fill up right away!!!

 

HAve fun,

Frnak

Edited September 4, 2013 by fbov

[bberg7794]

I have also noticed a discrepancy between the pump measured gallons vs. Trip 1 gallons.

 

During my second to last fuel, the pump measured 10.866 gallons where Trip 1 said 9.87 gallons.  This is a difference of 34.4 mpg vs. the 37.8 displayed mpg for the 373.8 miles traveled.

 

For my fuel up today, the pump measured 8.584 gallons and Trip 1 said 7.62 gallons.  This is a difference of 33.6 mpg vs. 37.9 mpg displayed on Trip 1 over 288.8 miles.

 

I would be hesitant to believe the pump, except New York State over-regulates everything.  You get to stare at the recent Bureau of Weights and Measures stamp right on the pump while fueling and also I happen to see the guy several times per year out measuring the tanks and certifying the pumps at different stations.  I even spoke with him a couple years ago.

 

Any ideas?  Has this been discussed in another post?

[Mamalou16201]

Ours always takes more gas and mpg is about 2-3 different. Which is rift?

[ptjones]

This is why I decided to go with what the C-MAX says, not what the pump says. It is consistent.

No one should never believe what the Trip Gauge says about gas used, It is wrong 90% of the time at least. Gas pumps are very accurate. Gas varies in BTU's which has effect on MPG.

Ours always takes more gas and mpg is about 2-3 different. Which is rift?

This is just the way it is, usually it is off by less than 10%. Just experiment by  filling up with Pure Gas once and see how close the gauge and pump are. All the vehicles I've owned have been this way. :)

Paul

Edited November 26, 2013 by ptjones

[ScubaDadMiami]

As long as I don't try to top off the tank, the two are pretty close.  I usually fill at the same place with real gas, Costco, which is pretty good about servicing their equipment.

[bigalpha]

I average about 2.8mpg less when I calculate the numbers using pump gallons vs. car gallons; and I have filled up at different gas stations.  On top of that, I have noticed the gas gauge changing - gaining and losing fuel...

[boilermax]

I have also noticed a discrepancy between the pump measured gallons vs. Trip 1 gallons.

 

During my second to last fuel, the pump measured 10.866 gallons where Trip 1 said 9.87 gallons.  This is a difference of 34.4 mpg vs. the 37.8 displayed mpg for the 373.8 miles traveled.

 

For my fuel up today, the pump measured 8.584 gallons and Trip 1 said 7.62 gallons.  This is a difference of 33.6 mpg vs. 37.9 mpg displayed on Trip 1 over 288.8 miles.

 

I would be hesitant to believe the pump, except New York State over-regulates everything.  You get to stare at the recent Bureau of Weights and Measures stamp right on the pump while fueling and also I happen to see the guy several times per year out measuring the tanks and certifying the pumps at different stations.  I even spoke with him a couple years ago.

 

Any ideas?  Has this been discussed in another post?

 

Some 30 years ago i worked for a company that made gas pumps.  One of the major national petroleum companies complained that our pumps would not hold calibration well enough to pass weights and measures checks.  All of our tests showed excellent calibration, right in the middle of the +/- allowable range.  Eventually we learned that it was their company's policy to set pump calibration right at the low calibration limit.  Then, if the calibration drifted just slightly lower, they would fail inspection.  

 

By setting calibration low they saved a fraction of a percent on every sale.  It's very little on a per-sale basis, but when you sell millions of gallons it adds up to a large amount of money.

 

That's long-winded way of saying that gas station operators have a built-in mechanism by which they can deliver less gas than they report and charge you for.

[bigalpha]

Well, at 8-10 gallons, is that difference enough to account for a 2-3mpg difference?

[ptjones]

Well, at 8-10 gallons, is that difference enough to account for a 2-3mpg difference?

For us it's just noise.  I've talk to a company here who installs pumps and we wouldn't see a difference..

 

Paul

[bigalpha]

I was thinking, the accuracy in the dispenser would also directly affect the Veeder-Root (or whatever else is installed) monitoring the whole system; especially if the operator was actively using the tank monitoring system to reconcile data and prompt a new fuel delivery.

[bberg7794]

Some 30 years ago i worked for a company that made gas pumps.  One of the major national petroleum companies complained that our pumps would not hold calibration well enough to pass weights and measures checks.  All of our tests showed excellent calibration, right in the middle of the +/- allowable range.  Eventually we learned that it was their company's policy to set pump calibration right at the low calibration limit.  Then, if the calibration drifted just slightly lower, they would fail inspection.  

 

By setting calibration low they saved a fraction of a percent on every sale.  It's very little on a per-sale basis, but when you sell millions of gallons it adds up to a large amount of money.

 

That's long-winded way of saying that gas station operators have a built-in mechanism by which they can deliver less gas than they report and charge you for.

Great story!   It reminds me of the scheme in the movie "Office Space."

 

Unfortunately, the two times I have checked so far the pump has been about a gallon high vs. the car.  I don't consider a gallon discrepancy "slightly lower" or "fraction of a percent."  Also, I commonly purchase 2.5 gallons in a plastic gas can for other than vehicle use.  I have had this can for many years and the manufacturer molded a line in it at exactly 2.5 gallons.  I have not noticed a difference between 2.5 gallons registering on the pump and the fuel level being anything but touching the line on the can, which still makes me wonder how the C-Max can claim 1 gallon less used.

 

I believe I read in the manual that Ford recommends only allowing the auto shut-off on the pump to shut off twice when filling the tank.  I was trying to top off the tank (old habits) more than this, but will begin using Ford's recommendation and see if the next few fuel ups are closer to what the car claims as gas used.

 

Thanks for the story.

[ptjones]

I believe we can scientifically figure this out by comparing Smart Gauge vs Actual and what kind of driving we did( %City vs Hwy ). I have Ipics of all my fill ups and actual on Fuelly with %City vs Hwy. On Smart Gauge divide Hrs into Miles to get average speed. Don't know when I'm going to have the time to do it. I believe there might be a clue there.  Also you could get a total of gallons used Smart Gauge vs Actual and end up with a percentage overall, I'm guessing in the 3-4% range :) 

 

Paul

[bigalpha]

I track all the data from 'Trip 1' with each fill up.

[ptjones]

I track all the data from 'Trip 1' with each fill up.

Great, see if there is a difference between hwy and city driving if you keep track of it.

 

Paul

[bigalpha]

There's definitely a difference.  I don't keep track of what % hwy/city driving I do because it's something like 90%+ hwy during the week.

[ptjones]

There's definitely a difference.  I don't keep track of what % hwy/city driving I do because it's something like 90%+ hwy during the week.

I was curious what your current MPG's are since your not posting on Fuelly? Also how far and fast do you drive on most of your trips? I would have thought you should be getting as least 40-42mpg. Do you happen to have a ScanGauge? What is your LifeTime Brake score? Just curious. :)

 

Paul