K30 CC 15-20mpg?

[Evane201]

hey guys,

I'm looking into purchasing a crew cab k30. It'll be my daily driver so I'm wondering if there is any way to get 15-20 mpg. I know that it'll never happen on a 454 so I'm thinking either a 6.2l diesel or a Cummins swap. Probably going to run Dana 60s, 35 bf goodrich allterains and a 3 inch body or shackle flip,with an np205.
I won't do much for towing besides small trailers less than 100 miles so I don't really need a 454. So what else could I do to enhance mileage and what are you getting with your build? if it makes any difference I may throw a flat bed on it.
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[jocko]

Welcome to the forum. I'm assuming you're talkin about a squarebody? There weren't any K30s made in the 67-72 era. But, stuff that improves fuel economy is kinda universal - 1st order of importance would be an o/d trans. Your diff gearing will need to be optimized for tire size combo with 1st gear and o/d ratios, all in the middle is gonna work out. And with 35's, 4.10 is probably the minimum gearing. O/D trans will help on the highway. If you aren't gonna haul a lot, I guess I'd question the goal of a K30 crew cab in the first place - that's a lot of truck and, even with an O/D trans, mileage will suck. 15-20 mpg is not a realistic goal. We're lucky to get that in a C10 swb with a 6 cylinder. But if you just gotta have one, well, THAT I do understand Again, welcome to the forum.

[special-K]

I got 12.5 consistent mpg out of this '72 K/20 4.10s, 4spd, 400 SBC, & 35/12.50s. I got the same with my '72 K2500 4.10s, TH350, 350, & 33/12.50s


I think the more torque the better, but with less cubes. I also drive 60-65 mph. Even in my '92 K3500 SRW 4.10s, 5spd, 6.5TD, 285/75s or 255/85s I found I got 2-3 more mpg keeping at that speed. I was getting about the same mileage out of that truck.

I think the K/20 did so well because it had enough torque (like a big block) with the lightest touch of the pedal. Never felt like it was working, just rolled down the hiway

[B. W.]

IMO, you could drive your rig for a decade with the stock engine @ 12 mpg by the time you "payback" the cost of the diesel conversion. ( I know, lot of variables, some will say it'll pay back in two years!) Jocko & special-k are spot on, overdrive & reduce speed - cheapest way to save money. If I felt froggy I might add fuel injection, relatively short payback on it.

[special-K]

I'm wondering what Jocko was, is this a total creation or a square body? Neither K/30s nor CrewCab/BonusCabs were available till later. A square body 6.2 with 700r4 will get you around 20mpg, maybe better. I got 22mpg with my '85 Jimmy with 3/4t 4.10s and 315/75-16s (35s). A big old 4wd that got mini-truck mileage.