I calculated the mileage that my Land Rover is getting. I have a 1999 Discovery II. I have been saving gas receipts since I bought it in July. The first receipt ended up not being legible, and so I only have two tanks to go on. Fortunately one tank was 89 octane and the other was 93 octane. I am really interested to see what the difference between octanes equates to in terms of mileage and cost/mile.
The Disco got 15.76 miles/gallon on the 89 octane and 16.05 miles/gallon on the 93 octane. I am tracking this using Google Spreadsheets and I have set the sheet up to be viewable by everone. 1999 Land Rover Discovery II mileage spreadsheet. Unfortunately it looks like you have to have a google account and sign in to see it. If anyone wants, I can just copy it into excel and put a link in the sidebar. Let me know.