Never had a truck with the 4.0, but my current daily driver Ranger has a 2.3. It has no performance upgrades, but makes decent power for what I use it for (mainly as a highway runner, but it also does some light hauling). My truck had some minor troubles that were'nt related to the engine itself (electronics and ignition), but after addressing those it has been very reliable. Started when the temps fell to -15 degrees, and has been on day-long trips in 100 degrees. Mileage is consistently around 23-25 mpg, which is the reason I bought this truck, but I have'nt been disappointed by any aspect of it, really. I'm sure that the 4.0 also has its high points, and hope that somebody who has experiences with that engine will post here to give you another side of the story. I looked at Rangers with the 4.0 when I bought my 2.3 version, but after deciding what I would be using the truck for 90% of the time, the 2.3 became the best choice. In the end, I think, that's what it will come down to in most cases.