When does MPG STOP getting better?
Team Owner
Joined: Feb 2000
Posts: 53,529
Likes: 77
From: Arizona
Originally Posted by cg205
I use a calculator. My DIC has shown lower mpg than I'm actually getting every tankful so far. Gas mileage fascinates me, and I've checked it on almost every tank I've ever used in all my cars. That's why the Vette amazes me so much. My wife drives an AWD 4 cylinder Pontiac Vibe (Toyota Matrix rebadge)....118 hp. I seriously doubt her car would have matched the 26.261 mpg I got in the Vette yesteday under the exact same driving conditions.
1) What was your difference between the DIC and your manual calculations?
2) Calculating your mileage to 5 significant figures? Just how accurate do you think your various gas pump meters are? I'm sure that there are laws that regulate their accuracy, but I'd bet there's more than a 1% variation there.
C6 mileage is great! C5 ain't bad, either...
Instructor
Joined: Dec 2005
Posts: 169
Likes: 0
From: Lawton OK
Originally Posted by Hoonose
2 things.
1) What was your difference between the DIC and your manual calculations?
2) Calculating your mileage to 5 significant figures? Just how accurate do you think your various gas pump meters are? I'm sure that there are laws that regulate their accuracy, but I'd bet there's more than a 1% variation there.
1) What was your difference between the DIC and your manual calculations?
2) Calculating your mileage to 5 significant figures? Just how accurate do you think your various gas pump meters are? I'm sure that there are laws that regulate their accuracy, but I'd bet there's more than a 1% variation there.
Gas pump meters have to be very close. Each state has a different agency that checks the accuracy of the pumps every year or so (some states may vary). I used to help my grandfather measure the pump accuracy when I was younger. He was the inspector of weights and measures for W. Springfield Mass. You take a 5 gallon measuring container with a meter on the top. You fill it up with the pump on the slow setting and once on the fast setting. If it is within a specific accuracy, the pump gets a seal with the date stamped on it. The seal cannot be broken or the station gets in big trouble. That way, it keeps stations from modifying the pumps to overcharge.
Next time you are filling up, look for the decal on the pump and it should tell you when the last time it was verified.
Team Owner
Joined: Feb 2000
Posts: 53,529
Likes: 77
From: Arizona
Originally Posted by youngs98
I calculate mine at every fillup with a calculator as well. It's always within 1 or 2 mpg of the DIC reading...usually the actual (calculator value) is better than the DIC.
Gas pump meters have to be very close. Each state has a different agency that checks the accuracy of the pumps every year or so (some states may vary). I used to help my grandfather measure the pump accuracy when I was younger. He was the inspector of weights and measures for W. Springfield Mass. You take a 5 gallon measuring container with a meter on the top. You fill it up with the pump on the slow setting and once on the fast setting. If it is within a specific accuracy, the pump gets a seal with the date stamped on it. The seal cannot be broken or the station gets in big trouble. That way, it keeps stations from modifying the pumps to overcharge.
Next time you are filling up, look for the decal on the pump and it should tell you when the last time it was verified.
Gas pump meters have to be very close. Each state has a different agency that checks the accuracy of the pumps every year or so (some states may vary). I used to help my grandfather measure the pump accuracy when I was younger. He was the inspector of weights and measures for W. Springfield Mass. You take a 5 gallon measuring container with a meter on the top. You fill it up with the pump on the slow setting and once on the fast setting. If it is within a specific accuracy, the pump gets a seal with the date stamped on it. The seal cannot be broken or the station gets in big trouble. That way, it keeps stations from modifying the pumps to overcharge.
Next time you are filling up, look for the decal on the pump and it should tell you when the last time it was verified.
1) Do you remember the variance allowed?
2) When will they get rid of the damn .9?
When gas was 17.9, I could almost see it. But 3.00.9? It's less than 1/3 of a %!
Race Director
Joined: Oct 2004
Posts: 10,089
Likes: 14
Originally Posted by Hoonose
2) Calculating your mileage to 5 significant figures? Just how accurate do you think your various gas pump meters are? I'm sure that there are laws that regulate their accuracy, but I'd bet there's more than a 1% variation there.
But that said, your accuracy in always refilling the tank to the exact same level isn't anywhere near that close. Nor is your odometer that accurate. I make it a practice to round all MPG calculations to the nearest tenth MPG, and even that may be a bit optimistic. BTW my long term manual calcuations tend to track closely with the long term DIC reading.
Team Owner
Joined: Feb 2000
Posts: 53,529
Likes: 77
From: Arizona
Originally Posted by shopdog
There are laws, and the various states have agents whose job it is to enforce those laws. In Georgia, pump accuracy is required to be 100 times more accurate than your 1% guess, ie pump error may not exceed 0.01 gallon per gallon.
