The Stovebolt Site Forums The Shop Area General Truck Talk Gas Mileage? I have NONE

Not sure if I'm posting this in the right place topic wise...

Got my speedometer working and according to it,my gas mileage is in the range of about 6-8 mpg. I have changed spark plugs, distributor cap & wires, carb rebuilt, new fuel line from pump to carb, and an oil change about a month ago.

I have plans to move my tank outta the cab and run new lines this summer, but not sure if there's a remedy for this beast in the mean time.

C-20, Straight 6 235, and I'm not heavy on the pedal. I might be running a bit rich, but there's no telling cause I'm a know-nothing about performance stuff. I just drive em'. Any input is appreciated. You guys rock!!

- Will

Unless you have a leak somewhere my first guess (and it's a guess) would be to check the accuracy of your odometer. If it's ticking off the miles too slowly it'll look like you're getting crap for mileage. I assume your county roads are one mile apart. Go for a drive and check the odometer to the mile markers. If you drive a mile and the odometer only shows 7 or 8 tenths you found your problem.

Tiny,

Thanks for the input, I'll check it out on the way home from work. If that ain't it, what would you suggest I do? Scrap it? The tank that is.

- Will

what kind of gas milliage shold a235 with a 3 on tree get in a 62 burb

More than what I'm gettin at this point. I would figure a burb should pull about 12-15 mpg, but what do I know? I can't even get my beast's up without help. Frustration...don't let it get the best of you.

Will,

Not knowing what kind of gearing you have in the rear-end or tranny, it would be kind of hard to guesstimate what kind of mileage you should expect.

I can tell you my trucks, one 235, one 216, and one 250 I-6's, all with original 4 spds, and 4:11 rear ends will barely see 10 mpg on a good day.

i dont even know what rear end gears i have its a 3 on the tree and all orginal(for now)

Jed,
i think you should betting getting better then 10mpg with an inline 6 even if your rear gears are 4.11s my now stripped 1978 Chevy Suburban got around 8 with my reg. somewhat on the pedal and hotroadin driving but if i cruised on the highway and not alot of town driving i almost got 12 and thats with a 350 V-8 with 4 barrel 4.11 gears stock 4 spd 1:1 4th gear 4 in. lift and 32 in tires so something ain't quite right with your sixes i think but then again i don't really know either
Nate

My '66 C-10 with a 250, 3-spd, and a 3.73 can usually gets about 11 to 15, It usually depends on where I am and how I'm driving. The gear ratio in your rear-end makes a big difference on the gas mileage that you will get.

Drew
--------------------
'66 C-10 stepside

I get 10 from my modified 350 and brag about it

Check your speedo over several miles. Even if the Speedometer is accurate, the odometer may not be. These old ones tend to stick. I've seen them run fine through the tenths, but take several seconds to click over the mile...or the tenths and the miles are fine, but the "tens" stick (etc.)

Will, my 78 C-20 350 with th400 and 4:11 gear gets about 10 mpg. It does not matter if it is up hill down hill loaded or empty. Looking to change to a 3:73 gear to improve mileage.

i get 12 on a good day on my 1/2 ton, 53 gmc, 228, 1 bbl, 4:10 4speed and am happy as can be. the rebuilt zenith did the trick!

my 39 1.5 ton with 235, crash box 4 speed, 6.17 gears and 33 inch tires gets 10-12 mpg around town with a 55 mph top speed

How fast are you driving it. If you are going a little too fast you're on the fine line of the power valve in the carb and it's dumping fuel. Slow down about 5-10 mph for a week and see if there's a major difference in mpg. If so, a gear change will fix the problem. You may have a bad power valve also,
Scott

Probably 12 or so is about the best to hope for anything with a 4.11 or near gearing. I used an old three speed overdrive and bumped it up to 16-18(depends on load and driving) and am happy as a cat in the milk barn. The nice part is in OD the final ratio is 2.88 since the old Borgwarner OD's are 30%, and you still have the underdrive 4.11's for trailer toting or heavy loads. It's a direct bolt in just needing a lockout cable and a couple wires--didn't use the kickdown switch. Did have to reconfigure the shifter rods a tad but the driveshaft fit. The price of the old 3 spd OD's has come way down because everyone is going to the 400R4 or other automatic OD's or to the T5 trans.

My '62 one ton duallie with a 355,mild cam,Q-jet,4 speed,4.10 gears and 31" diam. tires will do about 11 mpg at 60 mph. Of course,last time I was able to chart it,I was fighting a 40 mph headwind and sideways rain half the way. On a nice day,I could probably get 12-13 mpg.
Speed

My 58 Chevy 1/2 ton with 3 speed trans and 261 -6 get about 11 mpg on the hwy. Doesn't matter about load. You get that if you are empty or pulling a trailer with a vehicle on it.

the last time i was able to check, my speedo is unhooked, i got 9.5 in town and 12.5 in highway. i have a 235 with dual carbs and fenton headers, 2.73 rearend and 15" tires. the odometer has to be off because of the tires and the rearend. ron

My '55 1st GMC Suburban gets 12 to 14. 270, SM420 and 3.08 gears in the rear.

I know I have a fuel leak and have suspected that some tuning might get be a little better milleage but I'd be surprised if it ever got much better.

How tall are your rear wheels/tires?
Lots of highway driving?
or backroads and city driving?
Good Luck.
Colin

I have 80 series 16s on a 69 292 1bbl in my 59 1 ton and on a trip to Oklahoma and back I got around 17 mpg and that with 4.10 gears. Went around 50-55 the whole time - didn't push it. And that was with a load in the truck on the way back. (i was surprised too)

My speeedo's broke, and my tach doesn't work, but I did have a GPS that should prove very accurate. That's how I knew speed and distance.

This month's Street Rodder has an article on tuning for today's gasoline. The subject was a 427 small block F**d, and the owner didn't care about mileage -- only driveability and power. However, the article contained a lot of good info and steps that apply to any engine.

My 64 with a 292 gets about 12. I am thinking about a t5 conversion.

Jed,

I have the 3 speed on the column with the Eaton rear axle, I have no idea what the gear ratio is, something pretty low though, that old truck will climb a tree and pull down a house with little effort. Thanks, -Will

Colin,

I am running 235/80/15's on the Red Devil....

Scott,

What is a power valve? I be a dummy when it comes to specifics. Please use small words and type slowly I'm a dunce, but learning as I go. Thanks. - Will

It's an enrichment valve inside of some carbs to add fuel to the engine at higher RPM's to prevent a overly lean condition. Of coarse, your carb would have to have one for this to apply. I personally don't know what carbs do and don't other than the Holleys, so maybe some carb guy can chime in here,
Scott

Everyone's favorite, the Rochester B, has a power valve. On the B, it's not directly linked to RPM. It kicks in when the vacuum drops below 5" Hg.

For the record, I'm _not_ a carb guy. I just happen to have been reading the Rochester service manual today.

I looked through my manual and it tells me that my transmission is geared at 3:91. Does this help anything? Certainly not my wallet but it is a step in the right direction. Does anyone think that a re-rebuild of my carb would be worth the effort? I'd like to try and keep it stock, but if it is not worth the effort, what would be a good carb to use in lieu of my Rochester B?

I ran my truck until I got to a 1/4 tank yesterday and according to my odometer, I put 69 miles on it, using 3/4 tank of fuel. So with a 20 gallon tank, that's 15 gallons used. That leaves me with 4.9 mpg, if I did my math correctly. This seems on the low side. Maybe I should adjust my idle? Could I be dumping fuel into the carb and the fuel not being burned efficiently?

try lucas fuel additive,,,excellent stuff!!!
increase power and mileage...
i am a believer and will use it forever!

Food for thought....

My 2004 chevy 2500HD gets 13.4 mpg on a good day.
This is the "latest greatest smog-friendly engine" with all the cat converters, smog pumps. etc.

Im getting AWEFUL gas milage. I wonder what it would get if you stripped all the emmission B.S. from it at let it RUN! Im Guessing double mpgs....... wouldn't that be 1/2 emissions?????

BTW it is an awesome motor!

I had a B on my 230 in my 64, & got 16.5-18.5mph. I kept it under 65 mph, stock w/HEI w/34 degrees total advance, Taylor plug wires(try them, I was amazed), 3.73 gears & 3 speed & light foot. But I had it apart about 4-5 times before I was satisfied the power valve was not sticking-polishing it & the bore w/000 steel wool did the trick. brian