Looking at the newer 2016, 2017, or 2018 XJL (again)...

And was wondering if anyone had any information on which one is more "reliable"?

Reliable as far as Jaguar goes, lol.

 

Modern Jags have taken big steps for reliable side, since early days. Some say that Tata bring new thinking in the house. Strip the x351 XJ to the parts and you find out that it is builded up from OEM parts, exept chassis and interior. My one have +310t km (195t Miles) on the dash, and repair costs have been bit over 500€ last 5 years. (normal brake wear & services excluded)
On facelift (2016->) most issues fixed, exept Euro6 Diesel have got worse for short journeys, so take the newest one you have money.

 

No Diesels in the US so forget about all that.
Not many changes were made in those years as that car was soon to be discontinued. So the bigger changes if important to you were the center screen size increase and the different levels of software so you can install Carplay and Android Auto. Different levels of Blue Tooth and they finally added remote start somewhere in that range to.

Probably like all cars in that later built ones are better so get the latest year with the lowest mileage. I recommend getting a car with Jaguar's own CPO warranty if possible. But I had the 100K/7 year CPO warranty and used it a grand total of once in the 3 remaining years it was in effect. So good warranty but even better was I have had almost no problems in the 6+ years I have owned my 2014 XJR.

As I always post the real key to a good Jaguar experience is if you can DIY any of the repairs. I am currently having a small problem with a DPS valve in my AC system. The part was $130 and then my work to install it. Not to bad but I have seen the dealer charge $2000-$2500 for that repair.

But remember these are hard to sell cars and often sit for long periods of time on the dealers lots. Drive a hard bargain and be prepared to walk away from any car as they will be another along shortly!
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Remote start with the phone app - and not with the key FOB, correct...?

 

I am not sure as I have a 2014 so don't want to give you wrong info.
But I think your correct.
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Remote start is 2016 and up.
2018 and 2019 have the 10' display and would be the preferred choice if I was in the market.

 

That is stunningly, impressive information. Wow. 500 Eu. Deeply impresed and grateful. I managed to get my 1998 S600 W140 MB to 190,000 miles with almost no repair costs but that took an apprenticeship on my 1999 CL500 (hugely expensive) and the help of an expert tech so that I could set it up preventatvely. (and also buying that S600 from a one lady owner who babied it, and buying only from the two last MY's) Anyway, thank you, your post has given me confidence in a difficult moment...

 

2018 if you can find. they have the newer coolant hoses. 3-5000 to replace on prior models. if you can find 2016 or 17 that has already had done then fine. big expense to pay for. the coolant pipes have seams that will leak. should have been a jag and range rover recall but they never did.

 

some later cars (mine 2018) still have older plastic hoses (or did till I replaced them). Tell-tale sign is the older hoses are 2-piece glued together design, with clear large 'rib' along the weld line. you will see the upper hose emerge from under SC valley into front portion.

 

My 2019 has the upgraded seamless coolant pipes. But the thermostat housing has a seam, and it cracked at 22,000 miles. Also had the float in the coolant overflow tank go bad. Otherwise, it's been great.