The Stovebolt Site Forums The Shop Area General Truck Talk Consumption 3100 54

Hello
Few weeks ago I posted about my consumption

I use an iPhone app to register kms
My odometer is minoring 11% miles to the real distances
I’ve 19liters/100kms it’s 12,38 MPG
What do you think about that ?

My tires are 6,50R16C instead of 6,00R16C normally on this 3100 54 1/2T
Perhaps a part of the explanation.
Any ideas ?
Best Regards

I'm thinking that 12 mpg might not be too bad. my 2005 Chevy averages about 13 mpg. I did not check your math, because the only kilometers I know are the 5 and 10 km's (and I run those).

That is right in the range one expects from your truck. A set of 3.55 gears for the rear end should boost it up to 14.5 to 15mpg. Many are using the T5 overdrive transmission which some claim puts them near the 20mpg mark but I think 17-18 is more realistic. When your truck was new it was most likely used as a TRUCK so getting the job done was more important than fuel economy plus gas was in the 20-25 cent range in 1954. Radial tires can gain at least 1mpg. None of the above mentioned modifications are easy or cheap to do in France (I'd guess) and would take a long time to recover the expense with increased gas mileage saving.

I agree with Evan's statements (my comments/additions are in brackets/braces, below):

"That is right in the range one expects from your truck. A set of 3.55 gears for the rear end should boost it up to 14.5 to 15 mpg." [at 60 mph or less]

"Radial tires can gain at least 1 mpg. [adjust/play-with tire PSI to provide the best "balance" between steadiest/easiest steering]

Get 3.55 installation parts kit
- decrease oil leakage and looseness in parts.
- rear axle bearings often lower some noise.

Check, replace, adjust all front end/steering parts/seals - assemblies and alignment.

I have a 1951 1 Ton Canadian GMC (Chevrolet) and a 1938 Chevrolet Master, which is a sedan. They both have 216s in them. The 1 Ton now has 410 rearend gears and the Master has 422 gears. The 1 Ton gets excellent mileage, almost twice that of the Master. Oh and the 1 Ton is about 900 pounds heavier. I seem to remember years ago that mileage was not consistent vehicle to vehicle, even with the same model.

The items in my signature include most importantly the 4:10 rear end (replacing the 4.57). I get 13-14 MPG around town. 35-45 miles per hour. I'm happy with that.

Here's a data point:
1959 NAPCO suburban, stock 235 engine, 32" tires, 3.38 differential
After 3 hours on the highway 2000-2200 rpm (60-70mph), no braking, mild hills, it averaged 16mpg

Pretty good for an engine last rebuilt in the 1960s with 1/8" ring gaps!

I think stovebolt efficiency is greatly reduced when stop and go is involved... slow driving ~10-20 mph I bet it's below 10mpg.

As always the model "B" is the heart of everything plus EXACT timing, good plugs, etc. In the old days a point file and gap gauge was in glove box. My father one of the best diagnosticians I have ever known, ( Dad made a very good living at it). Dad and all the old time mechanics he and I knew claimed that the points should be paid attention to several times between oil changes. I get 19 mpg at highway speeds consistently on my pure stock 1954-3100 truck. I know this because like my father I always keep a little book of mileage and gallons of gas when I fill up. Remember.....proper metering jets for altitude or weight, and always use leather accelerator pump gasket and to compensate for unleaded gasoline one ounce of chain saw oil per ten gallons of gas. One should be able to get at least 18 mpg. Doc

Running 3.55 gears and yes, I'm getting 14+ MPG.