Driving to atlanta and back i was able to get 21 mpg. I didnt think that was too bad. I was running 76 as much as i could. My average speed was 71. I drove 487 miles with 23 gallons of fuel. I figured it the old fashion way and the on board computer was off a little bit. Thought id post this if anyone was wondering about the mpg for 410's. I saw a post a while back that claimed over 23.

 

Fuel economy is VERY engine speed dependent. With my 3.55's, My economy is best around 1600-1800 RPM (which equates to ~65 MPH @ 1800 RPM). At 70 MPH I drop off about 2-4 MPG off my average maximum and at 80 MPH I drop about 6 or more MPG's off my average max. I just ran from Chicago to Mississippi yesterday. The first 2 tanks were at an average speed of 75 MPH. The 3rd tank, well, all bets were off. I ran the portion of that from Memphis to Jackson, MS at an average speed of about 82 (thanks to 2 dudes in a new Camaro and some chick and her dog in a Camry running rabbit for me). I'll update this after I hand calculate the #'s over the next few days.

 

I have no idea how ya'll get such good mpg aside from maybe me being an auto. Even with hand calculation, I'm running 18.5mpg speeds 50-70mph +/-. This is with 3.55 too.

 

Ditto.

 

could be ur tune. not sure with my 331's i was getting 24 with 93 tune from brenspeed

 

20+ MPG on our V8's should be easily attainable if you're driving at least 50% highway or any other 50% or more steady state driving at or below 2000 RPM AND with only the rare occasion of "get on it". Although I have noticed that the fuels containing higher percentages of ethanol seem to reduce overall fuel mileage.

There are so many variables; terrain, road surface, environmental conditions, fuel... let alone the car itself.

 

I get 31 at 45 mph on a flat road with no wind and constant speed. :P

I get around 23 @ 70, 21 @ 75, and mid 17's at 90-95

 

3.31 to 3.73s, which is about a 12.6% increase in RPM cost me about a 9% reduction in Highway MPG.

 

That's odd cuz I run brenspeed tunes, so there shouldn't be any issues. Even before the tune I was running approx the same mpg. Not to mention I coast a lot so I'm usually easy on the throttle.

I don't take highway much, but they are local roads where its customary to do 65-70 in a 55.

Maybe shell gas isn't as good as I think it is.

 

ANY accelerating will reduce fuel mileage. Maintaining a steady state speed within the "sweet spot" (which is pretty much around 1600 RPM give-or-take about 300 RPM) on flat, smooth terrain and using gas that's not garbage will yield the best gas mileage. Expect it to drop with ANY deviation. Even having to slow down or stop on occasion and then get back up to speed, no matter how gentle, will reduce fuel mileage from the steady state conditions.

Are you sure your tires are at or above the pressure stated on the door jamb sticker?