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i have an 1984 scottsdale 4x4 with a 350 v8 and a sm 465 4 speed manual tranny 33x12.50x15 tires and 3 in lift in rear true dual exhaust with headers no cats and thrush turbo mufflers its been sucking gas so i calculated my mpg and its 5.9! why is it so bad i know this is not an economy truck by any means haha but i thought it should be a good bit better than that?
 

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Well the first reason its getting 5.9mpg is probably the 4 speed tranny.Overdrive would keep your RPM's down. The second reason is the bigger tires, and the third reason is that its probably got 2.73 or 3.08 gears. Not the best gearing for 33 inch tires. JMO
 

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TEC said:
Well the first reason its getting 5.9mpg is probably the 4 speed tranny.Overdrive would keep your RPM's down. The second reason is the bigger tires, and the third reason is that its probably got 2.73 or 3.08 gears. Not the best gearing for 33 inch tires. JMO
This is what I think it is but you may have a rich or lean engine problem a lot of things will make low mpg.
 

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Try a complete tuneup spark plugs,wires,air filter,timing check this may get you another 1-2 miles per gallon..
 

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I would think that you should be getting in the 10-12 mpg range. I know a guy you has a 77 F150 with a 460 in it and he gets sround 10. I think he has 35" tires on it
 

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My son's 84 K10 gets about 7-8, but he will have to tell you about the engine set-up etc...that ain't my gig.
 

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I had a couple Jimmy's with a 4.3 liter.They got crappy fuel mileage but it was never that bad.I had a 2004 2500hd with a 6.0 liter that I got about 6 mpg with.It had a couple busted manifold bolts which can mess with the air fuel mixture if air is leaking in.While I was replacing the manifold gaskets,I also replaced the plugs and wires.I also cleaned out the throttle body.It brought it up to 7 mpg lol.
 

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dce said:
I had a couple Jimmy's with a 4.3 liter.They got crappy fuel mileage but it was never that bad.I had a 2004 2500hd with a 6.0 liter that I got about 6 mpg with.It had a couple busted manifold bolts which can mess with the air fuel mixture if air is leaking in.While I was replacing the manifold gaskets,I also replaced the plugs and wires.I also cleaned out the throttle body.It brought it up to 7 mpg lol.
Gee...my '04 2500HD with 6.0 gets 12-13 mpg...I guess I should be happy?
 

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My '80 K10 short bed got around 16 highway, if IIRC?

350 CI V8, Rochester Quadra-Crap, Turbo 350 three speed auto (lock up converter when new - ditched it when I replaced the tranny at around 160K miles), 2.73 gears and 2" dual exhaust w/Thrush "almost mufflers".

Biggest tires I ever had on it, were 30" Firestone A/Ts.
 

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Was the speedometer/odometer recalculated for the larger tires? You will get a false reading if it wasn't. I know, I had an old S-15 Jimmy with a lift and 33" tires.
 

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Put a warmed tstat in, like a 190, 195 a warmer engine is more efficient. Long as your cooling system is up to snuff...
 
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