I have been driving my 94' Q45t going into 4th year. I use synthetic motor oil and transmission fluid (Mobile 1.) I change oil and filter every 3500-4000 miles. I have flushed the transmission fluid twice since I took ownership (every 30K.) Make the story short I take care of the car.

I was getting 19+ miles/gallon on my daily commute up until 6 month ago at which point it dropped to 17+ miles/gallon. Two weeks ago when I changed oil and filter and flushed the transmission fluid I also changed the air filter. Right after that I added Chevron Techron Fuel System Cleaner (20 oz.) to empty gas tank and added 12 gallons of gas. After 12 gallons ran out, I filled up and to my surprise I drove 465 miles before the low fuel indicator appeared. The gas mileage I got was 26.92 miles/gallon. The second full tank took me for 535 miles before the low fuel appeared. I GOT 28.037 MILES/GALLON.

What's going on here? I understand that I had a pretty dirty air filter. I hadn't changed that for over a year, but clean air filter can have such an amazing impact? Or was it the heavy dose of Chevron Techron that cleaned the fuel system really good?

I usually use BG 44k every 5000 miles to a full tank of gas and I had not seen any improvement at all. This time around I used Chevron Techron because I could not find any BG 44k locally.

I am static about this very pleasant gas mileage improvement. How can it be? I know I am going to change air filter at every oil/filter change intervals. Gas mileage specs when the car was brand new were 17/23. How can I possibly get 28 on city commute at 170K? Just unbelievable.

I just thought I would share this unbelievable gas mileage with you folks here. By the way, I need to add that I drive pretty hard.

Somebody added gasoline? Your odometer is off? The O2 are stuck at super lean? Or you are running on 6-7 cylinders and those injectors are not opening.24-25 mpg is possible with moderate highway speeds [55 mph] without AC - very level road.

Have to check the running at 60 mph injector open time with Consult.

I will have consult connected and get a read out of all cylinders and what you mentioned, injectors open time at 60 mpg. I'll keep you poested.

PS - The car drives pretty strong though. I'll be shocked if I have non-functioning cylinders.

Well. The main odometer is fine. The two trip counters, A nad B are off. Any idea how to fix that. Is it a matter replacing some electronics that lost its ability do some calculation? Part numbers please? :-)

Sure you haven't switched to kilometers instead of miles. 1.6 x 18 miles would create the 28 mpg. Push the reset inward instead of turning it.

Happened to me 7 years ago!

Is there a comedy section here in this forum? I need to put his post there. ;-)

I was well aware of the trip counters switching to miles/km but some how in this particular case I think I was so hyped up about those unbelievable gas mileages that it never crossed my mind. Oh well it was too good to be true. :-

LOL - I was getting ready to drive to Plano, TX in my 16mpg Q45 and sock you right in the eye.