Posted by richard schumacher on July 28, 2006, 3:01 pm
It is certainly not consistent. Thus one cannot assume that the amount
of fuel added at fillup number N is the same as the amount burned since
the previous fillup. Even if we assume that every gas pump is
completely accurate, this variability in the Prius gas tank capacity
makes a hash of trying to calculate MPG manually, except as an average
over many tanks.
And please don't top off. Topping off can saturate the fuel vapor
recovery canister and greatly increase emissions of unburned fuel from
the tank. Vapor recovery canisters have been around long enough that by
now topping off has become an old fart habit.
Posted by Bill on July 28, 2006, 4:38 pm
Thanks for telling us that Richard. This old fart will quit topping-off.
Posted by =?iso-8859-1?Q?mark=5Fdigital= on July 29, 2006, 7:01 am
Posted by Tony Belding on July 28, 2006, 11:15 pm
Something else to complicate your calculations. . .
You can't always trust the numbers you read off the gas pump. They can
be -- and sometimes are -- rigged to show more gasoline pumped than you
actually got. I've even heard in some cases they are even programmed
to be accurate up to the first five gallons, so people filling a
five-gallon can won't notice, then they start skewing the numbers.
Maybe it's just an urban myth, I've never set out to prove this
first-hand. But you know, gasoline scams have a long history (from
watered-down gas, to selling regular from the premium pump), so
jiggering the pump readings isn't far-fetched.
Tony Belding, Hamilton Texas
Posted by Davoud on July 29, 2006, 5:50 am
Tony Belding wrote:
Yep, urban myth, paranoia, or whatever you want to call it. It just
isn't done. That may not mean "never," but it means that such a
practice is exceedingly rare. Accidental inaccuracy is as likely to be
in your favor as against you. The flow meters are designed for high
accuracy, and that accuracy is tested by governments and by private
citizens who like to make sure that the station owners stay honest.
I've tested it at many stations (without meaning to) buy buying as much
as 50 gallons of fuel for farm tractors in five-gallon cans.
usenet *at* davidillig dawt com