Helen from SLC
I can't explain why the fuel economy increased after she moved from WI to SLC, but my guess would be driving habits (more highway miles, for example). She said she lost her additional mileage AFTER putting on new tires and has yet to get it back. Are the tires the sames size or are they different? Even if they are the same size, the new tires could be larger in diameter and now the speedometer is probably slow. In other words, the vehicle is now going faster than the speedometer reads. If this is true,then when the trip odometer reads 100 miles, the vehicle really traveled, say 110 miles, depending on how far off the speedometer is. Therefore, the fuel economy never changed, just the odometer. To verify this, she needs to drive down the highway and set the cruise on 60mph. While driving at this constant speed, time yourself between mile markers. It will take 60 seconds to travel 1 mile. If it takes you less than a minute, then you are traveling faster than 60mph and thus traveling farther than the odometer is reading. You can then figure the percentage that the speedometer is off, and calculate the loss in mileage per tank.