13.85 Mpg!

[nroden]

OK. Nothing great but 13.85 MPG is the best MPG that I have ever gotten. I keep track of my MPG always by righting down every fuel purchase info and my mileage in a notebook I keep with my oil changes, repairs, ect.
The lowest I have ever gotten was 10.05.
I think I could get 14 or more with the Pertronix ignition like I want. Think of what could happen with a new Edelbrock carb (or rebuild my Rochester Quad) and different rear end gears, TH700R4. (cant afford all this though... ignition most likely to get)
This was mostly highway driving going 50-55 that I got 13.85. Some of it was town going 25-40 MPH with stops. I wonder what all highway would be?? I have noticed summer gets better MPG than winter because in the winter you have to warm up. When I used that thank it was 60-70 degrees..... hmm.. its almost a science.

[dinnut]

thats not so good... you should upgrade to hei and get bosch 4 tip platinum plugs. that helps gas mileage A LOT. is ur 350 modded? big rear end?

[nroden]

I am not sure what the rear end is. Its stock. The 350 is completely unmodified original 350 that came in the truck back in 72.

[lukecp]

14mpg is actually pretty good for these trucks....the highest i have ever obserbed with mine has been 13.1 mpg....most get 10-12. When you have a low-compression V8 pulling a 4000lb truck that has no aerodynamics, 15mpg is usually the best you can get keeping you foot out of the gas pedal.

[Longhorn Man]

I'm getting about 13 - 14 now, I've gotten 16 once in the old longhorn...still trying to figure that one out.

[gmc67swb]

I GET AROUND 20 MPG IN MY TRUCK. THAT'S WITH 3.54 GEARS AN OVERDRIVE AND TBI.

[67cst]

i was getting 8 mpg but then i did plugs wires and air filter, i just put 93 bucks of propane in, wrote down my mileage and hopefully ill get 10 or 11 mpg now...

[Stocker]

Haven't checked mine in several years, but a cross country trip averaged 11.5. Triple tanks make it a PITA to check, and nothing but short trips just kills the average anyway. My truck doesn't get mileage - it gets yardage!

[72chevyLWB]

I have a 350 with vortec heads, larger cam, RPM air gap intake, 750 Edelbrock performer carb, headers, overdrive, 3.73's and 26" tall tires and I get 15.4 going 65 at 3,300 rpm

[EJ]

You know my old 1 ton crewcab 4x4 dually with a heavy flatbed diesel F&*d gets 14 mpg.

Someone needs to put a Duromax with an allison transmission in these trucks I think that would be one heck of a combo

[Carl71]

Agree with the yardage stocker.....Gas gage moves around more then the speedo

[Tx Firefighter]

My 3/4 ton work truck gets 21 mpg unloaded and 19 mpg pulling my trailer.

It also has 555 ft/lb of torque too. Torque rules!

My 69 SWB truck with a decent 350 and 3.73 gears got 13 mpg best ever. I put a built 700R4 overdrive in it and got.......13.5 mpg. That last half mile per gallon cost me 1250 bucks to get!

[nate68]

13.1 ist the best i've gotten with this motor. i need to set it up with a timing light and vaccuum guage since i never have

[nroden]

I wonder what these trucks came out of the factory getting? Did they keep track of all that at that time? Maybe someone has the info.

[Longhorn Man]

TX FIREFIGHTER...that just proves what I am always saying on here...lower RPM does not always equate to better MPG.
My GMC needs to run 75 - 80 to get the best numbers. Problem is, 75 - 80 is when the lack of aerodynamics really starts to hurt.
My engine is happy when it hits 3000 RPM. That is why I got such good MPG in the old longhorn. It was geared to where i was doing 3200 RPM right at 70 MPH.
I put that engien in the GMC with crappy 3.07 gears and my MPG went into the crapper. Down to 10 MPG overnight.

[cheyenne10]

Burnt a tank of gas this weekend with my new upgrades of rebuilt quadrajet and new HEI on my 402/T400 with 3.08 gears. Crusied fairly hard for around here 70-75mph and got 13.1 also. Much improved over untuned motor, points ign and old holley. Was getting probalbly around 8-9 mpg before

[BAD4X4]

Hey you guys I don't want to hear any complaints till you get 4mpg yes I said 4 in my old 84 1-ton chevy daily driver with 5:13 gears and 40'' tires. Oh and the 11.5 to 1 comp only ran on super. so quit being cry babies. ha,ha,ha I know my own fault. To also add to this I had a 72 1/2 4x4 on 35s with 3:08 gears and a small block all stock and it got 20 mpg on the highway ang 17-18mpg in town, I miss that old truck.

[1969 GMC]

35's and 3.08? sheesh. no wonder.
i swear that when i first got my truck, it did around 17-18-19 mpg, but that was all highway. I have all stock engine, SM465, 3.73 gears, and 32" tire. now it seems to do a little worse, but i do more around town driving. i can't bear to wind up my engine for more than 3k rpm for long periods of time. i usually cruise around 2500, which is about 60mph (i think).

[Longhorn Man]

As long as your engine sin't about to fall apart, it can hold 3000 RPMs for a while.
I did a 1000 mile trip in 14 hrs in the blue longhorn once, from Ft Hood Tx to Ft Knox Ky, had to pull over to J.B. weld my radiator back together, and stop every 150 miles or so for gas...but no sleep. I don't know what it averaged out to, and no idea what speed I was actually doing...but I know I held her just below 4000 RPM for about 1 1/2 hrs straight.
And for the record...I did make it there on time...but not with much time to spare.

[71-longbed]

best ive had is 15.88 mpg with the ol' 350.... much better after my rear diff. was shimmed correctly

[lukecp]

I've held mine at a steady 3k for about 3hours straight before....with a couple bursts up to 4k or so

[nroden]

New record for my 72... 15.38 MPG. I track this using the fuel logbook on Missourigasprices.com after writing down all the info in a little notebook I keep every time I get gas.
I drove from the Pamida store where I work in Lexington MO to the Pamida store in Trenton MO (its the ultimate of all Pamida stores... at least in Missouri.... never was a Places) The trip was
mostly highway going aprrox 50-55 MPH. Filled up at the gas station real close to store and drove up, went to Taco Bell across from Pamida, and then drove about the same distance back except on another highway. Went home and then filled back up the next morning. I am wanting to do another trip someday, on flatter road, all HWY and see what it gets.

[71-longbed]

nroden .. how many miles on your 350 ??

[lukecp]

That is excellent mileage Nick......you must have a light foot 50-55 mph proably also helps out alot, being that your enigne would be pulling ~2000rpm at those speeds, right around the toruqe peak of a stock 350. If only mine would get that, lol

[jorgensensc]

What! You don't cruise your truck over 3000, 1969 GMC
On the trip from California to Tx I drove for 14 hours straight, only stopping for gas and food, Slept, then drove for another 10 hours straight. I averaged 13.6 MPG with a mild 350 engine, th350 tranny, and 4.10 rear gears. Yes ladies and gentlemen, that was 4000 to 4500 RPMs at 70-80 miles per hour THE WHOLE WAY. Truck ran like a dream, and still runs perfect to this day. We didn't have 1 hiccup, except for the leaking fuel pump that I had just replaced, but didn't tighten it down quite enough. Ran out of gas in the middle of the Arizona Desert. At least it was at night.