22-24 Mpg Average....
1999 Buick 205K miles.
gas mileage 55-70mph = 24.1 mpg 70-80mph 22.0 mpg, 80-90mph 20-21 mpg 90mph+ 17.8 mpg
If the gas contains 10% ethanol I get 18 mpg driving 70-80mph!!!
When light goes on its always with 4 gallons remaining for me in the tank since it has a capacity of 18 gallons that means 72-100 miles to go... for me that is.
I bought a 99 LeSabre last fall. I learned the hard way when my gas light goes on I only have a little over a gallon left and need to get gas within 25 miles.
First, if you are only getting 24mpg maximum on your '99 Buick then something is wrong with your car. I'd get a mechanic to look at it. The age of the engine is practically irrelevant as there are test '99 LeSabres with well over a million miles, still running at the factory. That powerplant is proven to be good to 500,000 miles on marginal maintenance. Second, any ethanol mixture will be harmful to your engine in the long run and you simply should not use it at all. Finally, any ethanol mixture such as 10% and worse 15% (E85) produces about 25-27% less energy which means you will spend much more in the long run on gasoline. Good luck with your Buick.
to the above poster e85 is 85% ethanoland100% garbage. its not 15% ethanol.also i have a 92 lasabre and get almost 30 mpg highway
We have a 1999 LeSabre and have averaged 26 mpg overall driving for the last 3 years. Highway up to 31 mpg and city as low as 21-22. I use 3 ounces of acetone per 10 gallons of gas to counter-act the effects of the 10% ethanol. It keeps my fuel system and exhaust clean.