Precipitous MPG drop

[calauslon]

I was getting pretty decent MPG in my 06 HSE (about 15 city, and 18.5-19 hwy). That came to a dramatic end when I put in a fuel injector cleaner - thinking I might be able to eek out a few more tenths of a mile. Ever since then I have been at the 13 city. Still getting good cruising highway mpg, but it drops dramatically once I getf of the hwy. I am averaging 300 mile/tank. The problem seems the be the worst when I start the car. I could have a display range of 100 miles when I park at night, but when I start the car in the morning it is 90 (even in cold weather). There are no noticeable fuel leaks. I use only Chevron Premium, I get the oil changed and maintenance on schedule, and keep the tires are correct pressure levels.

Any ideas?

 

[jimbiram]

Not sure how many tanks of good fuel you have run since the injector cleaner, but I would get fresh fuel in that tanks ASAP. Sounds like the computer has made some adjustments in the burn ratio, due to the lowering of the octane from the fuel cleaner.