I am new to the forum and am currently shopping for an XJ, I prefer the long wheel base but am considering the standard wheel base if I can find the right one. At this point I have it down to two that I am interested in. One is a 1996 XJ6 with 70,000 miles and the other is a 2003 XJ8 with 60,000 miles. From reading through the forum and a book that I purchased, my sense is that the XJ8 will likely be more problem free overall than the XJ6.

At a high level, it seems as though the XJ8's are more prone to catastrophic engine failures due to a few weak links in the design (nikasil erosion, timing chain tensioner failure, water pump failure). It appears that most of these were addressed based on the VIN code off the 2003 that I am considering so I am not overly worried about these commonly discussed failures with the XJ8's. Conversely, the XJ6's from 96-97 do not seem to have much exposure to catastrophic engine failures. However, based on reading through the forums, the XJ6's seem to be more prone to potentially frequent annoying issues with keeping them running well. I am not sure if I have over generalized how these cars will fare for me moving forward. I recognize that both are older cars and the treatment by the previous owners may have more to do with the experience that I will have than the design of car. I would appreciate folks who are more familiar with these cars to give me some insight. My intent for the car is to be a fair weather driver probably putting about 5000 miles per year.

One more thing the, the door jamb label on the 2003 caught my eye in that the manufacturer name in green that I think is intended to be a security watermark, is upside down. Does that strike anyone else as odd? Here is a picture enlarged to show the security mark:

 

All the reasons you state for concern are hard to determine as reasons to own any vehicle. Your speaking of a car that is 21 yrs old and one that is 14 yrs old. Either would be considerations for maintenance repair just from the age. If they run and drive well, they will probably serve you well. You sound like you have mechanical ability, so look at it as a badge of accomplishment to keep either on the road for your enjoyment. Thing is there are many threads and good folks here to try to help notice an issue before it becomes a failure.
As for the one to choose, that is up to your taste....myself I'd lean toward the '03. For the watermark labeling, that is a manufacturers choice.

 

Go with the 03. It would be useful to tell us where you live. And the prices!