K30 15-20 mpg?

[Alex V.]

If left pretty much stock, a Vortec 454 set up just right might yield 15 on the highway in a K30. If you want it to look "tough" it's gonna cost, one way or the other. A Duramax or Cummins should easily exceed 15, maybe even 20, but you have the initial cost and effort put into the conversion.

[Evane201]

For now I'm going to purchase that suburban and the c20. I'll drive the suburban for a while while I repair the few rust spots and repaint the c20. Then I might tackle rebuilding that 350 that's in it and just leave it the way it is or down the road swap motors and convert the c20 to a 4wd.

Thanks for all of your help! It is much appreciated!

[shootracing22]

My 12 valve Cummins swapped 89 crew cab short bed with a 8" lift and 37" mud grapplers 4.56 gears a 4l80e trans with a gear vendor overdrive gets 15.5 on the interstate. Which is really good for a truck its size. I had it on 35" toyo MTs for a while and got a little better than 16 per gallon.

[mongocanfly]

Been following this to see where it lead so ill put in another 2cents..on my 81 c30 I considered a duramax swap for my ol 350..after factoring in the extreme cost of the diesel swap I went with a lq9 ls..still not the cheapest ls swap but I'm happy with the results..if I baby drive it it "might" get 14-15 mpg..put a trailer behind it and thatll cut it in half...I've had many a friend of mine brag about the mpgs they get with their diesel but it amazes me how many of them are just guesstamating..never put it to pencil and paper..the few that have usually get their feelings hurt...that 25-30 mpg they think their getting usually winds up being 15 or so..all of these are 3/4ton 4x4s of all makes..the other thing that amazes me is how much time most of them stay in the shop..seems like every trip to the shop they make the mech bill starts at a grand and goes up from there..I can't figure how with todays technology that the new diesels gives so much trouble...i know there's exceptions.some people have great luck with them...we've got diesel tractors that are 40 yrs old that don't give a minutes trouble..on the flip side though youll find it hard to beat a diesel for towing..really no comparison to a gas burner..