11–20 of 33 posts
Unless you find a fast station that sells ethanol free gasoline (and you'll know because it costs more), gasoline is cut with up to 10% ethanol. 1 gallon of ethanol is equivalent to 2/3 a gallon of good old gasoline. So to keep things simple, if you buy 10 gallons of gasoline @ 20 mpg is 200 miles. But 10 gallons of gasoline with 10% ethanol filler is really 9.6 gallons, that's only going to get you 193 miles. That's…
Do you always fill up at the same station or same brand? Maybe they are adulterating the fuel (higher ethanol content, etc.). You can get test kits for ethanol content. Maybe your vehicle needs a tune-up? They could also be fiddling with the dispensing measurement, saying that you put in 12 gallons, when it was really only 11. Harder to check than you might think, since some operators were adjusting things to come ou…
Gasoline and diesel usually sell by volume, and if the temperature of the fuel is cold when you purchase it, you get more kilos per volume than you do when the dispensing tank is warmer. There is quite a bit more expansion & contraction of hydrocarbons with temperature than many peoople expect.
They’ve probably rolled out the E15 again: https://carbuzz.com/feds-fight-gas-prices-easing-ethanol-res...
gasflation
Maybe your tires need air or your engine needs a tuneup or it's windier. Or not.
You shouldn’t be noticing more than a 7.5% drop between E0 and E15 gas, which would be a pretty hard swing in gas composition. What % do your figures show?
Gasoline and diesel usually sell by volume, and if the temperature of the fuel is cold when you purchase it, you get more kilos per volume than you do when the dispensing tank is warmer. There is quite a bit more expansion & contraction of hydrocarbons with temperature than many peoople expect.
I live in California. Our temperature variation is not that large to explain this difference in fuel efficiency.
Fuels containing a higher amount of Aromatic class hydrocarbons, (or just lesser "light" hydrocarbons) will have a higher density (lb/gal) compared to fuels having lower amounts of the heavier molecules.
Also the aromatics bring with them higher antiknock ratings which can also be better for efficiency in a number of different engines.
When acceptable octane rating is achieved by ethanol content instead, it works good too, but fuel efficiency is reduced chemically because alcohol does not consist of only carbon & hydrogen, alcohol molecules also contain oxygen which provides bulk but not energy, so alcohols can be considered to already be "partially oxidized hydrocarbons" to begin with. It's really the oxidation process of the burning fuel that provides the energy, and alcohols just have less to give than hydrocarbons.
Miles per gallon is the conventionally understandable measurement units, and even fuel injectors meter the fuel in by volume, but actual energy obtained and resulting engine efficiency depends on performance per weight of fuel, not exactly per gallon directly.
During changing seasons I like to feel the metal part of the gas nozzle for temperature during dispensing. One of the worst times is when a tank trailer has been sitting in the sun a while before delivery, and it's 95 Fahrenheit when it's not even that hot outside. I like it much better when a trailer comes from northern locations where the fuel is less than 60 degrees, then I buy more but don't fill it up. It's nice when it is colder fuel to purchase and if it's a hot summer once the gas warms up to ambient conditions you end up with more gallons than you pumped, but if you are not careful the gas tank will overflow "autonomously" if you fill it too much with cold fuel when it warms up like that :0
There are a number of other factors too, but this one is often overlooked.