Hey everyone…I wrote a quick little program that calculates MPG and other info. The more useful feature is that it allows you to see what you’d pay/how many miles per tank you’d get with different octanes for those of us with vehicles that “recommend” premium but can use regular.
For example, I found that using premium in my Cadillac got me an average of 3 more MPG (25 MPG mixed average, vs 22 MPG before on regular), so I’m actually saving a bit of money by filling up with premium.
Anyway, it’s just a basic little thing that hopefully some of you will find useful, I made it mostly for myself to save doing the math everytime. 
Enjoy, and let me know what you think or if you’d like any changes, or find any bugs.
Jad
Oops, here’s the file! Just download and run it (scan it with your anti-virus first if you’re not too sure about me…
Thanks Jad. Appreciate it.
Glad you found it useful, Steve. Let me know if it has any bugs to be worked out, I just put it together today.
That’s really quite neat. Mind you, I only have to use regular in my Impala, but still… quite neat.
You need to make a program now to determine how much more energetic someone is after drinking a large coffee from Timmy’s, versus a crappy sludge they call coffee from any other store.
Thanks!
And no kidding! …Timmy’s is calling me right now…haha
Your calculation is making a BIG assumption. That every vehicle will have the same delta in gas mileage from using regular or mid or high-test. You can’t make that assumption.
My 4-runner is recommended to use 91 octane. Using hightest I get about 23mpg highway. If I use regular I average about 21.5mpg.
Actually, the program isn’t supposed to be used for making predictions. It’s only really useful once you have your averages (as you do) to see what the cost benefit is, or isn’t. You have to calculate the different average MPG yourself and then plug it in there, or, use the program to see what you’d need to achieve to save money at different octanes.
For example…if you are averaging 20 MPG on regular, and you have a vehicle that is designed to run on high test, you can use the program to see what kind of MPG you’d need to achieve using high test to make it equal out in cost, or even save money, based on the current cost of different grades and what you’re averaging on regular.
Hope that explains the purpose of the program better.
To use your example, I looked up the current regular, mid, and premium cost/gallon in Louisiana (random). $3.77, $3.87, and $3.97, respectively.
Plugged those numbers, an 18 gallon gas tank, and your average of 21.5 MPG on Regular into my program and got the following results:
On Regular: $67.86/tank, and 387 miles/tank
Selected Premium, and adjusted the “possible” MPG to your already calculated 23 MPG and this is what I got:
New cost per tank is $71.46, but now you’re getting 414.36 miles per tank.
So although you’re paying an extra $3.60 per tank at those prices, overall you’re saving $1.20 per tank due to the additional miles/tank. And, you’re treating the engine the way it was designed to be treated.
All this can change due to different prices at the pumps, or varying MPG calculations, which is what I wrote the program for.
Hope that helps explain its use.
Addendum: The “savings” is calculated based on the additional miles you are getting on Premium, or Midgrade fuel. That is, in the example above, you are getting an additional 27.36 miles using Premium, so I calculate how much it would cost to achieve an extra 27.36 miles at the Regular gas price and then compare that to what you paid extra for Premium.