I have a 97 xj6 and its bulletproof but I've been told the x308 was horrible for reliability. What made a drastic change in reliability? What are common problems with these X308's

 

I wouldn't say the X308 are horrible. If you shop right, you can find a nice example for a very decent amount. 3 major issues to look out for:
1) nikasil lined engine - many claim that after a certain amount of miles nikasil will hold and perform better than iron lined motors, but I don't buy into that.
2) non-sc XJ - automatic trans A-drum
3) plastic timing chain secondary tensioners

I like the 96-97 xj6 for its reliable motor, one of the best engines Jag ever built.

 

The best X308's are the last 2002/2003 models, as they avoid the numerous 'teething troubles' of the earlier ones. 2001 models are ok too but will need the secondary tensioners upgrading to the metal ones.

 

I have a bullet-proof 2003 XJ8 -- one of the best cars I've ever owned.

 

My 2003 XJR is rock solid. Now you see my posts in relations to rubber parts failing, but thats expected on a car thats in Florida and has 150k miles on it...

 

My 2002XJ8 VDP has been a remarkably dependable luxury dream for 87,000 miles to date. Most of the replacement items seem to have been done under the Jaguar Select Edition extended factory warranty. I'm reminded repeatedly the I probably will have transmission and other problems on the horizon, but it certainly has been a dream so far!

 

Come in, the water's fine. I had a 1995 XJ6 LOVED IT- swore I would never get a newer one.
After buying my 01 XJR and working through the FEW issues it has had I love this one waaay more.

 

loved my x300 also owned her 6 years, but been stood a while and rust beat it floor pannals chassis etc so bought x308 69000 gen miles jaguar service history , boy do i LOVE this car ohyeeees!!!