The 4.0 is one of the most Durable engines Ive ever had the delight of starting and driving. I have 4 of them, all running and driving, in my possesion. my 87 has 291,+++ hard driven miles on it, and dosent burn more that a quart in 7,000 miles(my usual OCI). My 96(which Is the 1st year of the main bearing Girdle) has 248,??? miles on it and is as smooth as silk, and burns quart or less in a 7,000 mile OCI as well. My 99 is another story. It didnt burn any oil, amazingly, in 5,+++ miles I drove it with a egg shaped hole made in the piston by the wrist pin of Cylinder #2 with a seized upper Compression ring, and seriously worn piston skirt. Micro specs told me that only 3 thousandths out of normal wear occured. So ball hone with new standard size Speed Pro pistons are getting pressed onto old rods, with Hastings cast rings awaiting assembly. The 24 hours of Dremel porting to all 12 valve Bowls and Intake runners will hopefully pay off with some even quicker acceleration in this 2 wheel drive Cherokee. My Beloved SilverStone Metallic 01 Cherokee has 64,??? miles on it, and dosent burn, or leak anything. Though I do watch the Coolant level in this Jeep, as the 0331 cylinder heads can crack between #3 and 34 exaust ports, and leak coolant into the oil. Looking thru the oil fill cap will show you exactly where the crack would be.
