A guy could write a 5 page essay to cover that question.
Indeed, but Lenguevo is one of the few Guys left on Moparts that actually contributes to this site, has a sense of humour/a bit of sarcasm and is more like what Moparts used to be like. So lets do something for him as opposed to the rest of these lazy Twits that never give anything to the site and ask this same question twice a month.
You want to buy a second-hand Cummins from someone who has the first clue of how to look after a diesel engine.
1. If some Meathead has a "hot air kit" or some stupid straight-pipe on it: walk away. Don't even waste your time. The explanation is long, but just trust me, they don't have a clue and that's all you need to know.
2. Talk to your local Cummins shop and ask them if they know of anyone with a Dodge they might be willing to part with. These guys know diesel power not these Posers on the Internet with a chip and lift-kit in their truck.
3. For your Brothers' own good, just simply steer clear of Fords. Latest report from a good Friend that is an HD Mechanic, even the latest Ford (engine number 7 or 8 I think since the 80's for that hopeless operation) is littered with expensive problems: transmission, turbos. Leave it to Ford to create jobs for Mechanics.
4. Isuzu. Well, it's pretty well-known that I can't stand anything Blunder Motors puts out, but Isuzu does know what they are doing. Total shame you have to take the crap tin-can they are wrapped in. Not worth the trouble or humiliation of driving a vehicle that our Gov lost 11 billion on, or being seen in one of those gawd-awful ugly things. Have some pride Man, you are on a Mopar site, tell your Brother they are under top secret recall like the gm ignition switches for example. gm would rather see dead Customers than build a proper vehicle, so you take your chances with them. Avoid at all costs.
5. Direct from the Guys I know at Cummins: as soon as the engine was bumped to 300hp everything has gone downhill since. In a nutshell, that is all you need to know. The ISB was never meant to have ridiculous 3.73 gears behind it, or some funky "pre-injection event" to reduce the noise. Both equal one thing in a diesel: piss-poor fuel mileage. Sheldon may argue with Me, but it's all I've heard since the '03/04's came out.
6. I've owned a few, and the best is the '94 to 2002 with 3.54 gears. They will go down in history as the best-looking, and best performing Cummins ever. Many know this, and Ebay listings prove it. The ride is harsh, the noise from the Cummins is almost unbearable, but they are the real deal and you just have to live with it.
7. Get a brand-new Cummins. Disclosure: I have been out of this since the 6.7 festival of failure, so......... if you have deep pockets, have work for the engine to do (read: no short trips and should be loaded 50% of the time), and have a good dealer it could be the way to go. I'd lease one though: if it turns out to be a fuel-buring pig and needs to go to the shop every once in a while for some emmission excuse, you don't want to own it. Somewhere, off-warranty, that B!tch will cost you ten grand and I've run into many new Hemi Owners that don't miss their old diesels for that very reason.
What I've typed out can be found in various forms on the Cummins forums, and is real-world experience: I've been around diesel my whole life and in my opinion: diesel was once the future but those days are long gone. The fuel is more expensive, the maintenance is expensive, the
REAL WORLD fuel mileage sucks and they are problematic.
Get a 6.4 Hemi with 4.10's and stop looking at diesel: The Manufactures are purposely rail-roading diesels into the ground by crippling them. Anyone that can't see it isn't following the big picture.
