New diesel modder here
 

Hi all,
I bought my big old diesel suburban to move and tow what ever I need.
Its not built for speed :turtle: or off roading (2wd).
I mod for power and economy, which is easy to do on a diesel.
I got the truck in 2006 and started cutting waste vegetable oil into the diesel fuel almost right away. At the same time I started modding for power and economy, over the years from 2006 to 2010 I did several mods to pick up between 5 to 6mpg. Most of those gains came from intake and electric fans.
Starting in 2010 I tore the engine down and nothing was off limits. I built the engine back up with just about every affordable power and MPG mod I could think of and I am working on doing alot more.
Not much is off limits.
A 1984 diesel suburban that gets 30mpg is not out of the question.

I use to have an 84, 4x4 Suburban which got 19mpg, with 185,000 miles on the original 6.2 non turbo, automatic. What did you do to the engine that helped?

http://ecomodder.com/forum/showthrea...uck-18187.html
That is my post where I talk about what I have done in the past, what I just finished doing and have not tested along with all the parts I have bought while I am away and will be installing when I get home.
When I pulled the old engine apart it had 235,000 miles and was getting over 26mpg.

My friend had an '85 (I think) non turbo 6.2 4x4 Suburban that got around 22 mpg. I always regretted not buying it off him when he sold it, and to make matters worse I still see it around (10 years later) just to remind me of my poor decision. If I did need a large vehicle for something I would certainly look for a 6.2, good luck with your quest for 30 mpg.

Yes my truck started out at about 21mpg.
GM didn't start turbo charging them from the factory till the late 80s or early 90s. By that time they had changed the heads to produce more power and less economy, 3.08 diff gears were no longer put into most trucks.
Back then diesel was cheap and they were going for more power and moving away from economy.
Last time I ran My truck I was getting 26mpg, since then the new engine went in and is untested. I think everything I did internally should be good for 2MPG, I dont think that is unreasonable.
Thanks to banks engineering any year non-turbo 6.2 or 6.5 diesel can be turbocharged and as of last week they still offer product support in the form of fairly pricey replacement parts.

With the 6.2/6.5s, it's all in the precups. The smaller precups used on the earlier, non turbo 6.2s were the ones for the mpg. The larger 6.5 turbo precups were great for power, but the mpg dropped.

That is why I reused my 6.2L heads on the 6.5T block.
You read my mind.
Also my 6.2L "c-code" heads are known as the small valve heads, but they do not crack between the valves like the later 6.5L heads with larger valves.
So I picked economy and durability over power.

I am a fan of the 6.2/6.5. Heath Diesel and Kennedy Diesel keep me inspired. It's like with anything, once you understand them, they're good engines.

Go for it!
 

Go for it, man! I think you should be able to do it. I've recently broken into the 30's with my Cummins. Hopefully I can keep it there. There's a few other guys on here that have 3/4 & 1 ton diesel trucks that regularly run tanks in the mid and high 20's. I find it wonderfully amusing that some of us are getting mileage that we're only "supposed" to get with compact cars!

Is it a manual or automatic? It'll be easier to do if you have a manual.

Only problem that I see is I am getting rid of my 31 inch goodyear RT/S tires and putting on 31 inch yoko AT-S. My friend did the exact same swap, identical tire size and all then lost almost 1mpg.
The problem with the goodyears is after 10 years they have dry rotted to the point of tread seperation and they were only good on dry pavement going in a straight line any way. In the rain, snow, mud they would not grip the road at all. If my truck didn't have a factory posi differential I would have gotten stuck in my own yard and my parents drive way numerous times. Being strictly on road only is not good for a work truck that pulls a trailer for fire wood among other things. Few of the trees I cut are right next to the road.

I have the more efficient of the old GM autos, a TH700R4 with converter lock up. Also my truck is a half ton.