I would agree with stranger as to making sure the engine is tuned. Probably wouldn't hurt to have the injectors gone thru and rebuild the pump. Get the rail pressure set up a little higher than stock with about a number 12 button in the pump. Also as he mentioned make sure the overhead is run correctly. That is critical and it should be run at least every 50,000 miles or you will beat the copper out of the injectors. With the ulsd fuel try adding some howes or lucas to boost the cetane level. Dragging a belly dump especially on job sites tends to use more fuel than going down the road. One other consideration is how many miles are you actually putting on the rig? Even boosting fuel economy by 2mpg and running 1000 miles a week will only net you a 75.00 savings.Anyway that's my 2 cents worth

ever consider a transmision with a deep reduction so you could use a more highway friendly rear gear without loosing th ebottom end?

I know that's pricey but if you want to keep it (and I would) then it's all stuf you will end up doing anyways.I wouldn't get rid of it. The piece of mind "knowing" your truck is priceless. You buy something else and you on't know what you will get.
Pittsburg diesel injection can set up a cummins pump like nobody else. Great thing is that cummins pumps are cheap. You can buy one from them instead of having to pull yours and wait for it. Call them and talk to them, they are the best cummins performance people I know of

What about water/meth injection? Quite a popular mod to increase mileage and cool exhaust temps on diesel pickups. I'm about to add that too my duramax. Reasonable cost of about $500.00 and u pick up added hp too! Just a thought!

Suggestions here may improve fuel mileage a bit but not much. I ran a similar setup hauling logs and was happy with 4 mpg. Running in a 55mph state and the work you do I would stay with the rear end ratio you have. If you do a lot of running empty a 15 speed would help ( the big jump in top gear was designed for work trucks.)

I appreciate the input from everyone on this post I made (quite awhile back, in fact). Thanks again to all.

I've been told not to sell my Pete, by more than one driver. It's not far from becoming a classic and I must admit that it's been a trouble-free power unit. She needs a good paint job and some cab interior work but mechanically she is sound. It just sat for a full month here in Oregon. I went down to start it a few days ago and it fired off like I had run it just yesterday. I can't complain about that. I stay on her for maintenance like a fly on a roadapple. So many owner/operators just drive them until they drop. You just can't expect a truck to stay running without taking care of it. That old girl never ceases to amaze me when I see so many newer rigs sitting along the road in their death throes....I just steam on by.

The mileage improvements here won't cost me an arm and a leg (tune-ups, etc.) and if, with everything considered, I can see just a 1 mpg increase (that might be optimistic but just don't know) it'll be worth it. I know driving habits play a big part in one's mileage. There are truck drivers then there are truck drivers.... I drive mine like I have an egg between my foot and the throttle. Funny how that works....when you drive for someone else and aren't footing the fuel bill you drive differently that when YOU'RE paying for it.

Thanks again to all for your experience and expertise. Finding a good Cummins mechanic may be a job but know they're out there.

Rod

I just read this whole thread an no one mentioned the easiest and first thing i would to get better fuel mileage out of your rig. I would change the gear ratio in the rears and get it more realistic like 3.73 or so would do wonders for the fuel millage and still be able to pull well. The tune up and over head and every thing are givens but the easiest and quickest way to get better fuel millage is go to a taller gear and bring the rpm down on that motor.

you don't want to bring the rpm down too much on this engine. Giving it a little more rail pressure will give more power and better economy. The small cam is not designed to run much lower than 1500 rpm. If you try pulling the rpm down and lugging you will start breaking head bolts. For a 55 mph state 4.11 single over 13 and tall 24.5's are a good combo. The tall rubber gives more ground clearence for dirt work and they cap very well. If you are running a lug tread design that also will lower economy by 2 tenths a mile also.

That's beacuase he's working of road where he needs that gear

howabout an RTO18?

Hey I was reading this thread and had some thoughts.

First is that your Small Cam 350 is designed to run from 1700-2100 rpm. It's fuel milage will never be as good as a newer engine. Running it below 1700 rpm can damage it.

Does this truck have a air fan or a solid driven fan? If it's solid driven that will kill your fuel milage.