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Gas mileage
Thread Starter
Instructor
Joined: Apr 2005
Posts: 164
Likes: 0
From: Alexandria VA
Gas mileage
What kind of gas mileage do you guys get? I expected not so good gas mileage with my new 75, but I didnt think it would be this bad. I have an 18 gallon tank and got about 60 miles on the last 1/2 tank!!! (If you're doing the math, that's <7 mpg!) This cant be right - could I be leaking fuel somewhere before the carb? If I am, its somewhere hot b/c it's evaporating before I see a leak. Car has always smelled a little like gas when I fire it up, but I chalked it up to being an old Vette.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
theres a reason we say "its a Corvette ...we didn't buy it for gas mileage" instead we measure smiles per mile....its much higher
Last edited by bobs77vet; May 9, 2005 at 02:17 PM.
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Race Director
Joined: Feb 2005
Posts: 16,100
Likes: 17
Originally Posted by jaycjackson21
Yes, but SEVEN MPG?!?! Any ideas what could be holding me in the single digits? Running way rich? Fuel pump leak? Performance seems fine.
Nervous or jackrabbit drive
High speed
Short-run operation
Excessive fuel pump pressure
Choke partly closed after warm-up
Clogged air cleaner
High carburetor float level
Stuck or dirty float needle valve
Worn carburetor jets
Stuck metering rod or full-power piston
Idle too rich or too fast
Stuck accelerator-pump check valve
Carburetor leaks
Faulty ignition
Loss of engine compression
Defective valve action
Clutch slippage
Seriously,if you smell gas........I got 118,465 on original carb,no gas smells........
Last edited by rihwoods; May 5, 2005 at 09:53 AM.
Race Director
Joined: Sep 1999
Posts: 11,361
Likes: 383
From: Plano TX
I have an 18 gallon tank and got about 60 miles on the last 1/2 tank!!! [/QUOTE]
What do you mean by "half tank"? When the needle shows 1/2 full there is much less than 9 gallons in the tank. My gauge works about like this:
Full tank = slightly above full on gauge
50 miles = Full
100 miles = 3/4
130 miles = 1/2
160 miles = 1/4
So as you can see the gauge is not linear.
What do you mean by "half tank"? When the needle shows 1/2 full there is much less than 9 gallons in the tank. My gauge works about like this:
Full tank = slightly above full on gauge
50 miles = Full
100 miles = 3/4
130 miles = 1/2
160 miles = 1/4
So as you can see the gauge is not linear.
Drifting
Joined: Nov 2003
Posts: 1,634
Likes: 4
From: Northern NJ
St. Jude Donor '04 & '05
Originally Posted by bobs77vet
theres a reason we say "its a Corvette ...we didn't by it for gas mileage" instead we measure smiles per mile....its much higher
. Not the right car to be driving if MPG is your main concern.Now that said, 7 MPG does seem a bit low. Are you actually recording the amount of gas used? The 75's were the first year (I believe) of the fuel tank bladders and very often these collaspe restricting the amount of fuel you can put in the tank. In my case, when the guage reads empty I can only get about 12 gallons in the car to fill it.
I'd suggest you top off the tank, drive it for a 100-150 or so miles using your regular routine and top it off again. Then do your calculations based upon mileage driven and how many gallons it took to top it off the second time. Now you will know tha real MPG you are getting. In my case with a 70+K miles on an L-48, 4 spd w/a carb in need of attention, I'm getting about 15-16 MPG.
FWIW. Good Luck!
Last edited by ACECO; May 5, 2005 at 11:58 AM.
Thread Starter
Instructor
Joined: Apr 2005
Posts: 164
Likes: 0
From: Alexandria VA
Thanks guys - I'll check it out. Good times are definitely outweighing any gas issues (or any other issues, for that matter!), but I would like to get her up into the double digits if I can. 
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by jaycjackson21
Thanks guys - I'll check it out. Good times are definitely outweighing any gas issues (or any other issues, for that matter!), but I would like to get her up into the double digits if I can.
why not put Marrying Julia Roberts on that list too.... you pick the order
Burning Brakes
Joined: Nov 2004
Posts: 1,028
Likes: 0
From: San Antonio Texas
Originally Posted by vabeachvette
My 73 350 gets 12 mpg.
79 L82, consistently gets 12 - 13 mpg. has for years. sounds low but i know several people with "modern" SUV's who get less. and know several people with Vortec V-8's in their trucks getting about
12 -14 mpg. this with "modern day" fuel injection and "computer controlled" ignitions.
guess when you play you gotta pay.
Race Director
Joined: Jan 2003
Posts: 15,176
Likes: 88
From: State of Confusion
I have an '82 with the CROSS-FIRE INJECTION motor (quit-laughing), 700R4 A-OD transmission:
with the OEM 2.87:1 rear gears, it got 23.9 MPG over a 238-mile trip (exclusively-highway), and after a swap to 3.73 gears, it has gotten 17+ MPG over a 430-mile trip, featuring at-least half the trip using back-roads, country-roads, and city-driving.
with the OEM 2.87:1 rear gears, it got 23.9 MPG over a 238-mile trip (exclusively-highway), and after a swap to 3.73 gears, it has gotten 17+ MPG over a 430-mile trip, featuring at-least half the trip using back-roads, country-roads, and city-driving.
