My 4.0 has been in my 1991 ranger sense 2005 it was token from a 1997 ford explorer that had 29,000.I've started out with 65000 on the gauge now i'm flited it ones to 000000 now i'm at 10000 now.But no long distance driving.But i do tow a 14X5 R&R old rental tandem trailer hauling scrap metal for the last 18 year's.I've been told if you changed the oil and drain the radiator ever year and stay on top of the maintenance I've been told sense its fuel injected It can last upwards to 500K or longer the 4.0 did not have the problems the 3.0 with weak heads
The early 4.0 had a problem with oil pumps and sunken valves.
But do the full maintenance every 80K that hoses water pump valve covers Even your fuel injectors and the O2 plugs autolites plug wires the radiator If its been in there 3 years swap it for a new one Plastic dose not hold up well over time
the Fan clutch and the plastic fan it gets checks in it change it.
Do your brakes when your suppose to.Drain a refill you rear end oil.
sense the std trans uses trans oil Just keep a eye on the leavel see if the oil is turning brown then change it Automatics 80K drop the pan and drain the oil put a new filter in put new fluid in Check your truckl for leak around the yoke it likes to leak there.
Be a gauge watcher are trucks are special they come with a full gauge package.Its not the trucks fualt if it blows up on you.
It give you amp warring before it goes remember to flush the heater core.If you have the copper and brass heater core keep it ther better then the alum ones cus you can have them rodded out by a radiator shop they last long time.
The rangers that come with the 4.0 and std trans is a good combo they last a long time.
My 93 4x with the 4.0 ohv was my favorite truck (and vehicle) ever. Only issue I ever really had with the motor was the fuel rail gasket failed and it had a hell of a vacuum leak. Used very little oil between changes, high teens in mpg (super cab, manual trans, 3.73’s) I’m not sure that I’d want a ohc 4.0 but I’d gladly have another ohv. Mine was almost at 180K when I retired it. It literally did everything I ever asked of it.