Author Topic: 79 k20 5.5 mpg  (Read 576 times)

Offline Wadell

  • Newbie
  • Posts: 5
  • Newbie
79 k20 5.5 mpg
« on: December 09, 2022, 11:46:57 AM »
Hopefully someone can help me I have a 1979k20 truck stock 350 4 speed im getting 5.5 miles per gallon . Is this normal for this truck or is something wrong

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6313
Re: 79 k20 5.5 mpg
« Reply #1 on: December 09, 2022, 05:44:54 PM »
The simple answer is that 5.5 MPG seems low.  However, driving style has a HUGH impact on fuel mileage as does maintenance history, gearing, state of tune, condition of the fuel system, the environment in which the vehicle is used (flatland vs hilly terrain), tire size and pressure, vehicle load, the time spent idling the engine vs stop-n-go vs highway usage, and the quality of fuel.  So, the answer to your question is a resounding, "could be normal... could be something wrong..."
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline JohnnyPopper

  • Senior Member
  • ****
  • Posts: 2266
  • Old Goof
Re: 79 k20 5.5 mpg
« Reply #2 on: December 09, 2022, 07:45:31 PM »
Copy that on tire PSI...35 might be a more comfortable ride but it cost you biggly.

I take mine to just under the limit cold.

How many miles are on the motor? If you don't know, I would do a compression test first thing, or while you're doing a tune up.

It can and will tell the tale of your engine condition.

I only touched two of bd's scope, there's a lot more to go.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline Big Dee

  • Newbie
  • Posts: 20
  • Newbie
Re: 79 k20 5.5 mpg
« Reply #3 on: December 12, 2022, 09:36:12 PM »
The brakes might be dragging. lift the front and spin the tire. friction will increase m.p.g.
bd is right in everything written, so pay close attention to that wisdom.
85C30...

Offline Jimbo302

  • Newbie
  • Posts: 3
  • Newbie
Re: 79 k20 5.5 mpg
« Reply #4 on: December 18, 2022, 06:55:41 PM »
For reference, my 77 C20 2wd, 350/th350, 4.10 rear, 31" tires, got 14mpg on the last tank .

Offline Wadell

  • Newbie
  • Posts: 5
  • Newbie
Re: 79 k20 5.5 mpg
« Reply #5 on: December 21, 2022, 06:48:49 PM »
Thank yall for the wisdom I will look at all of the ideas

Offline Shifty

  • Junior Member
  • ***
  • Posts: 765
  • I bleed Bowtie red...
Re: 79 k20 5.5 mpg
« Reply #6 on: December 22, 2022, 08:12:56 AM »
87 V20 TBI350/400 4.11 gear w/33's, I get 10 smiles/gallon.   :D
87 V20 Standard Cab Longbed (current)

87 R30 3+3 Longbed (days of yore)

98 C2500 ext cab longbed