So, I did it. I drove the speed limit to Clarksville. (When I say I drove the speed limit, I stayed within 5 mph of it.) I have my results which I think you will be rather surprised at.
On a normal tank of gas I used to get about 26-27 mpg. Today I saw gas for 3.67 a gallon. My car usually holds about 12 gallons. So that's approximately $44.00 a tank. I usually fill up about every 5 days. There are 365 days a year so I fill up 73 times a year (WOW that's a lot!). SOOO 73 times a year at $44.00 a tank is $3,212.00 a year on gas (MY GOODNESS!)
Driving the speed limit, however, I got 30 mpg (I think it was 30.8 but I'll go with 30 just so it won't be as confusing). That's 3 more mpg than before. So for every tank of gas I'm going about 36 miles farther than before. Which is about an extra gallon per fill up. I drive about 18 miles to and from work each day (36 miles) so I'm going to say I can add an extra day to my fill ups, making it every 6 days. So 365 days/6 is 60.8 so 61 times a year. 61 times a year at $44.00 a tank is $2684.00.
A savings of $528.00 a year! Seriously, aren't you going to be driving the speed limit from now on????