-My eyes almost popped! I knew we were getting good numbers but 25.5mpg? I went up to LK George in the Adirondacks this wkend. Last week the rearend install was finished on my 88Iroc. It now has a 3:23 posi. Of course I didn't get the speedo gears finished up, but I was running a steady 2250rpm. I figure roughly that it's about 72-75mph. The speedo was reading 85mph. Anyone else seeing these kind of numbers? On the way home I was running same speed except there were some slowups and delays, had the a/c on about 1/2 the time, 24mpg. I think it's awesome. I'm washing the K&Ns today and am making a run up to Boston this wkend coming and will verify my math. The maf is descreened,coolant bypass @ the throttle plate,desmogged,hooker headers, and 1.6 roller rockers, and the 3:23., Joe

 

Yes.

18-20 commuting, 23-25 highway.

It's a little harder to get those numbers these days, since it's out to the track almost every week.

 

Good numbers. Dyno Don reported 26mpg in his car. It also will turn a 12.8 @ 107 in the quarter mile. Best of both worlds.

 

Yeah, 25mpg highway has been seen on these cars before. Not too shabby for a powerful V8.

 

You haven't yet gotten the right speedo gears? Did you then adjust your odometer reading to obtain the corrected mileage reading? If you've swapped from 2.73 to 3.23 then the number of miles actually travelled is 2.73/3.23 X the odo reading. That math works for the speedo reading as well.

You probably figured all that in, just checking, and I average around 24 with my puny LG4.

 

well i dont know if anyone will believe me . just got back this week from san antonio and a trip last month to key largo i got as high as 29.5 to 26.6 m.p.g. . lo3 , t5 , 3.08 gears , headers , 3" ex. , 1.52 roller tips , MSD system ,K&N . i had to double check figures . could not believe the numbers . just shows what a proper and well tuned 305 can do . im a cruiser not a racer and my baby is my daily driver .

UNCLE TOM

 

-I did the adjusted math, then did it again. That's why I was surprised! The only thing I can figure is that at the slightly higher r's (2250) I was turning the motor was more into it's power band and just not working hard. I spoke to my brother and he says he's getting 16-19 in his 2004 Suburban @ 70mph on highway trips so I guess these numbers are pretty close to being good.

 

And with higher gearing the motor doesn't have to work as hard getting up to speed.

 

I was always afraid people wouldn't believe me when I told them about my 92RS. LO3/T5/open element car, pulled down 28.3-29 consistently on the highway when cruising 75ish. Mind you that was with VERY little use of the go-pedal to get to that speed.

 

i have an l03 and i got 28mpg on my last tank. not a single mile of highway driving, all was in town, and it includes plenty of WOT runs, and a couple races against my friends foxbody.

no joke!

 

I have pulled down 25-26 mpg with my 83 LG4 5-Speed with 3.73's believe it or not. The 3.73's are not spinning that hard with the 5-speed. Only mod to the car is no cat and a Eldebrock .442 .398 lift camshaft.

 

That's better highway MPG than the Lexus Hybrid - and not too far below many of the others...

http://www.fueleconomy.gov/feg/hybrid_news.shtml

 

when i first got mine, i did a road trip... took er pretty easy 'coz i wasn't quite comfortable with it (my first car and i'd never driven stick before) and pulled 27.4 mpg averaging about 65 mph. completely stock, minus cat.

 

wow, how in the heck do you do it... LOL!

I can pretty much see my gauge go down while im cranking it over getting it started, let alone get 25+ mpg!

 

If your car has the TH350 (from your profile) its understandable. Overdrive works wonders for fuel economy.