Topic: MPG what do you get
in Forum: C3 Fuel, Emission Control, and Exhaust Systems
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Jeff,
If you want better gas milage, change the axle ratio to 2.78 and put in an overdrive.
Then you will have a dog like mine.
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Since putting the 700R4 in, we run anywhere from 19 to 27 mpg (Effingham trip) depending on how "bad we treat her", as Joel said. 55 mph on the highway yielded best results. Before the 700R4...15-16
LIFETIME MEMBER # 191
Lifetime MemberPhoenix, AZ - USA
Joined: 3/13/2004
Posts: 537
Vette(s): 1975 Stingray Nomad Wagon, with Daytona front, custom hood scoop, dual side vents; 420HP 350; Doug Nash 5 speed; 1980 rear end W/4:11 gears; Cherry Red metallic paint.
exactly the same as my 74 4 speed, just ran with it last week and was happy with 15mpg @ 70-75.
Lifetime Member #36 
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Lifetime MemberHOWELL, NJ - USA
Joined: 5/18/2004
Posts: 6812
Vette(s): 1979, Targa Blue (72 Color), Pace Car rear spoiler, L88 hood, Dark blue factory interior, 525HP 406, HD 700R4, 370 gears,Steeroids, composite rear spring, TT IIs wrapped in T/A Radials.
[QUOTE=DaveM]Hey Barb, don't you just love that first gear!
Dave
[/QUOTE]
Davey, I love my first gear but the BFG TAs just haaaate it!! 
Believe it or not, with the 700R4 in OD mode, the Lukester gets anywhere from 16-18 HWY.
On local roads, its GPM, not MPG!! 
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"Ruby" is my daily driver, and after the ignition upgrade, running on regular gasoline (87) I've had a chance to run several tanks of gasoline and she is giving me an average of 18 miles to the gallon. City and highway mix 50-50. I can't wait to take a long trip and find out what she'll do on a highway cruise.
TommySSE 2011-07-24 22:38:45
Tommy
1980 Project Corvette - (Need suggestions)
1982 "Ruby" (Ain't She Sweet!) 
On the last trip to Effingham I managed almost 23 mpg @ 70 mph. I had to go this slow due to a nasty vibration. I love my Tremec 5 speed.
TKO500 5 spd.
Borgeson Steering Box
Born 8/1981
Sequence #3975
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Lifetime Member #26
79 L-48 with 3.55 gears and 350THM auto:
Average of about 14 mpg with the former Rochester Carb. Just upgraded with a GM performance parts manifold and Holley 4160 carb. New dual exhaust (nice chambered dueal kit from Midamerica). Much better throttle response, much stronger acceleration off the line - about the same at upper RPM. Gas guage seems to drop off a little slower, but hard to really tell as I seem to be on it frequently so I can enjoy the really crisp exhaust note.
Guess it will be awhile before I drive it to maximize mileage....I am guessing sometime around the year 2035.
In the end, we didn't buy these things for their outstanding economy.
C3: 1979 Corvette Coupe, Auto, L-48, Red/Doeskin (my wife's fave);
C4s: 1986 C4 coupe (SCCA road race car), satin black, 4+3, Z51 package, L-98; & 1993 C4 coupe, white, 6-speed, LT-1.
in Forum: C3 Fuel, Emission Control, and Exhaust Systems
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