I’ve had no issues!! With all the rumors flying around that it causes leaks, enhances leaks that already exist or any other issues about leaking it may cause; from my experience the rumors, complaints, comments, opinions are all unfounded, so far. I switched out about 1000 miles ago and I did have a small oil leak in my 01 Limited with approx. 40k on the engine and as of now I see no exaggeration of the leak I had before the switch; it actually seems to have stopped or slowed down to nothing. So for anyone thinking of switching; do it, you’re XJ will be fine and run better; I noticed mine does.
I'm using Mobil 1 5w30 with an oversized Mobil 1 filter # M1-301 which gives you an extra quart of oil. I chose it because of the cold start-ups in Baltimore, MD, where the temp has been below freezing for the better part of the last 2 months with no relief in sight.

Here’s a cross-reference for the larger filter sizes:

Brand /Stock /Over-sized
AC Delco /PF13 /PF2
Fram /PH16 /PH8A
K&N Gold /HP-2004 /HP-3001
Mobil 1 /M1-204 /M1-301
Motorcraft /FL332 /FL1A
Napa Gold /1085 /1515
Purolator /L14670 /L30001
WIX 51085 51515

Hope my 2c helps..

 

I will second all of that!! I switched to Mobile 1 High Mileage 10w-30, and have stuck with it for the past year and a couple months.

 

switched my 89 corolla over 2 yrs ago at 200K now 240, no issues

 

The only time switching to synthetic oil will cause an oil leak, is if you already have an oil leak, and the only thing slowing it down is a build up of sludge/dirt. A synthetic will clean this away, which is where this garbage that Synthetics cause leaks. With that said, Mobil-1 is extremely over rated.

 

I have used Royal Purple in every vehicle and just switched my XJ over and it actually runs smoother, 1 mpg better and slight increase in oil pressure. The problem is Royal Purple is expensive as hell, but, I'm a believer

 

^^ This


Also, if everyone hasn't read through this, I HIGHLY recommend it.
http://www.bobistheoilguy.com/cms/in...=article&id=84

 

Yep, its a myth. Everytime i say it doesnt cause leaks people think im crazy. Everybody will eventually catch up

 

I've read through that. Based on many UOAs (used oil analysis) 5w40 seems to be the best wieght for an XJ. The 5w helps with flow in cold temps, and the UOAs showed much less iron wear with a 40 weight at operating temp than a 30 weight.