'84 K10 getting 8.9mpg....is this normal?

[trevor73402]

I have been curious for a while on what the MGP were on my 84 SWB K10. I was thinking that it couldnt be very high because it seems like it sucks the gas pretty quickly. This truck is all stock, 350, 700R4, no lift, 31" tires. It has a recent rebuild on both motor and trans (within 10,000 miles). It has stock manifolds, Magnaflows, and NO cats.

I checked the MPG on it over the past week and it came out to 8.9MPG with a combo of town/Hwy driving in on average 95-105 degree heat with the A/C on MAX the entire time. Is this about average compared to everyone else? It seems a little low, even for a 4wd and running the A/C.

Any adivce to on helping to increase this besides the usual tune up stuff like plugs, wires, cap, etc.... The truck runs great, nice and smooth, no issues at all.

[Zane M]

It will be interesting to see what others have to say. Your milage doesn't seem too far out of line to me considering you have been running the air constantly.

[Stepper562]

Seems too low to me...especially with a 700R. Could be your gearing and the 31'.
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[Littlebuddy]

I get the same in my truck, Ive got 6" of lift and 35" tires though...

[DetroitDan]

I get the same with my truck, and I've got a th400 3 speed, cast iron t-case, 6 wheels, 4 doors and 4.10 gears. Oh yeah, I've got a 454 with a 4 bbl too. I would expect to see 12-14 with your combo, depending on gear ratio. You likely had 3.08s with that motor/tranny, but not for certain.

[trevor73402]

Hmm,
Well I guess it is low then. I was wanting to know what others were getting. I'm not positve what gears I have, I assume the stock setup. I suppose I need to check my plugs, wires, etc....
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[donut]

Depends on gearing, driving habits, condition of tune...
Full time 4wd?

Turn off the ac and check it. If nothing else, I'd be curious.

My father was happy if he could get 10 out of his '84 (and this was just a couple years ago.)

[meter swinger]

Ill take that anyday with my 454 powered dually
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[USSkoval]

That's low. When my '88 Burb was still stock, 1/2 ton, 350, 700r4, and 31's... it averaged 12-13. Now that it's lifted, bigger axles, etc, it still averages about 11mpg. Heck, I have to REALLY work my 454 Burb to get less than 9mpg.

[Littlebuddy]

Originally Posted by USSkoval

That's low. When my '88 Burb was still stock, 1/2 ton, 350, 700r4, and 31's... it averaged 12-13. Now that it's lifted, bigger axles, etc, it still averages about 11mpg. Heck, I have to REALLY work my 454 Burb to get less than 9mpg.

What type of Axles/Gears are you running? I would love to squeeze even 2 more MPG out mine.

[tucsonjwt]

This topic comes up often here. My experience after owning 3 old squares - expect no more than 9-10 mpg regardless on a big old heavy truck. If you have a 1/2 ton, overdrive trans, low number rear end, all stock, light foot on the accelerator, fuel injection (like an 87), small block or V6, you can get 14 city/18 highway or slightly better. 14/18 mpg is what the new GM full size pickups get, and they are designed for fuel efficiency. My 2010 GMC Sierra ext cab 4.8L, 4speed auto trans, 3.08 rear axle got 15.5 city/ 18.5 highway with very careful driving - so I would say that is the maximum achievable on a V8 pickup. I did have a V6 2000 Silverado that got 19 city/23 highway, but you won't be pulling any heavy loads with a truck like that. Others will post here with much better gas mileage numbers - but I never got that, although all of my squares were 3/4 ton trucks, which means I carry an extra 1000 lbs. of dead weight.
Some common tips an gas mileage:
All tune up parts in good shape or replace - spark plugs, wires, cap , air cleaner
Very light touch on the accelerator when leaving a traffic light
Let off the gas when you are approaching a red light and coast to a stop
Pump up air in tires to max inflation or near it (watch your tires wear sooner)

[tucsonjwt]

One more thought - make sure you don't have a fuel leak. I had a leak at the fuel inlet nut on the carburetor which I never noticed because the gas would evaporate as soon as it leaked on the intake manifold so I never saw it - just smelled it - so I did not see it until it got very bad. Also, I just noticed a leak at the fuel pump - looks like it was leaking for quite a while but since the fuel dripped off directly to the ground because of the part location I never noticed it- I would have noticed it if I was under the truck with the engine running, something I never do. Bottom line - if you notice any gas smell check the fuel system completely with the engine running, maybe have someone you trust rev the engine while your check it out. I also had fuel slosh out of a full tank of gas because the rubber hoses at the sending unit or to the hard lines were cracked or loose - you might see traces of fuel leaks on the tank or lines - stains on the hose or tank.

[C-10 simplex]

How are you calculating mpg?

[78c10]

my '78 2WD 350 4Bbl/TH350 with 3.73 gears and 235/75/r15 tires would only get 13 on a really good day. average, with air running, was between 9 and 10. you have the 700r4, which should help, but yours is 4WD, which in my experience negates the benefit of the 700r4. And, overdrive will only help you out on the highway, it won't do much for you around town.

I noticed a jump of about 1 mpg with the edelbrock performer intake, but ymmv.

[Stoney]

My 84 K5 gets about the same.

[trevor73402]

Originally Posted by C-10 simplex

How are you calculating mpg?

Number of gallons used divided by the total miles driven.

[Goldfinger]

do you live on a mountain/drag strip. that's ridiculously low.

[karlbenz]

my 85 k10, 350, 700r4, carberated, on stock 31's gets 15. I can get better when tuned up. thats no a/c also

[bradford]

Mine is getting about 8-9 mpg also but I know its not running right.
I have a timing light on the way and a new distributor.
I put a new edelbrock 600 cfm carb on it, new fuel pump and new plugs and it made no difference on mpg but runs alot better.
I will see this weekend if the new distributor and timing helps.
Oh, mine is an 83 K10 short bed, standard gearing but I have a 4 speed manual with granny gear.
I get that mileage at 65 mph with AC on.

[dman1982]

i just drove my 84 from jacksonville nc to south of the boarder sc, and i was getting 10 to 11 on the high way and i get a little better when im in the city, kinda wierd...running 35's with a six inch lift

[Your41Plague12]

That's about what I get, but I have a K20 sitting on 38's with a TH400 and a mild 350. Yours should be better, for sure.

[veinbar]

Everything Tusconjwt said sound advice. I think you can achieve better fuel efficiency, so start experimenting with some of these items. Check for leaks, tune or rebuild your carb, tune up you truck, set your timing properly, repair exhaust leaks, max out your tire psi, and manage your foot. You will see improvements.

[kris's66lwb]

Make sure you odometer is correct that will affect it mins off i thought i was getting 10 average i did some mapping of my routes and it turns out im gettin 15

[veinbar]

Originally Posted by kris's66lwb

Make sure you odometer is correct that will affect it mins off i thought i was getting 10 average i did some mapping of my routes and it turns out im gettin 15

Good point. If you have a GPS (Tom Tom, Garmin) they will track your actual distance and speed. Or if you have a smart phone, there are several free apps out there that do the same. I have a GPS Speedometer app that displays my exact speed, my avg speed, my overall distance traveled, and has a place to plug in my fuel usage to get my MPG avg.

My speedo doesn't work, my gas gauge doesn't work, non stock tire height, and my dash light are out. I run out of gas all the time. I had to get smart and this app helped me a lot.

[dman1982]

oh i also forgot to mention that mine has a couple gas leaks and im getting that....gonna be fixing those leaks this weekend