I just filled up my tank yesterday and calculated 34.6 MPG's.I had 533 miles on that tank of gas with 3 gallons left in the tank.
I tuned the car up back in February including NGK iridiums plugs,wires,cap and rotor,and fuel filter.I replaced my paper air filter with a Spectre air filter about two weeks ago.
I also used Auto-RX since I bought the car about a year and a half ago.I can actually pass on the highway without downshifting out of fifth to pass.
When I bought the car it had 71K miles and now has 109K.
I had to post because this is the first time ever getting this kind of MPG's with this car.

 

Four or six? Did you calculate by miles on tank or by actually calculating miles driven and gallons added?

 

Four with a 5 speed.
I calculated the miles driven 533 from the last fill up then divide the amount of gas that went in.

533/15.4

 

Sounds high, unless the wind was at your back. Keep track of mileage for next 5 tanks and see if it stays the same.

 

It seems very high.I was shocked when I figured it out.
I'll keep this site posted.

 

My last two fill-ups were 30 mpg and 32 mpg.
Working on my third tank now.

 

wow! thats very high.. my 93 4cyl auto usually gets 25 or so. I'm a little heavy on the throttle and drive ALL THE WAY across the city to get from home to the dealership. I'll try some of the stuff you listed though. A lady that used to work at teh dealership had a 2004 and she was getting 35mpg also.. every time.. since she bought the car. It is a vastly different platform, but still much higher than teh advertised mpg.

 

the website is www.auto-rx.com
I'm not affiliated in any way with them.I've used this stuff in four cars that I own and it works.
I also shift the car around 3K RPM's.I'm sure that helps alot too.