Originally Posted by Mr_Draco
Because according to my test's it's cheaper in the long run.
First off let me say the cost for 93 as pretty much stayed the same at the gas station I use for the last 2 years at $3.70. Now when I filled up at 1/4 a tank, I had to fill up every 7 days. No matter what, I had to get gas every Wednesday on the way home for work. It was like clock work for a year. My bill for filling up was always between $54-$56 every week and according to my credit card bills it averaged out to $55. $55 a fill up times 52 fill ups comes out to $2,860.
Back in Jan I started something new. I started to push it until right around the time the light would come on. It's always on at round 35 miles to go so I know when it's getting ready to come on. I found out that by doing this I could get one extra day between fill ups and the cost of one extra gal of gas (instead of my buying 14.5-14.8 gals I'm now getting 15.5-15.8 gals). Since Jan my average cost for a fill up is $58.50 every 8 days, which comes out 45.5 fill ups a years. $58.50 a fill up times 45.5 fill ups a year is $2,661.75. This is a $200 savings every year just by do this.
Your analysis is flawed. If you drive the same number of miles, getting the same MPG and pay the same price per gallon then your total cost will be the same no matter when you fill up. If your total cost has changed then one or more of those three variables has changed.