New XJ6 Series III Owner | Eager for Tips

Hello folks,

I’m a proud new owner of a 1985 xj6 with the 4.2 an 65,000 miles. She’s in good+ condition for her age, but I’m looking to get her back into excellent shape. I would love to hear ALL your recomendations for doing so! Here’s what I’m already planning:

  1. Oil change, brake fluid, and coolant. I’m thinking Castrol GTX high mileage 10w30 for the first oil change as I’m in a colder climate (upsate NY) and want to clean whatever’s built-up over years of very little use.
  2. Fuel injector cleaner.
  3. Ziebart is running a promotion on underbody rust treatment and undercoating. So I’m scheduling that as well.

Would love additional tips to get this cat back in top shape!

Welcome aboard.

  1. A bit light for this engine. Your car is not high mileage. Very low for it’s age!! Were it not for your clime, I would go to 20-50. It is fine in mild climes. In between should be a good option.
    2.I have little faith in the injector cleaners. But, one seems good. Techron by Chevron. Big can plus a load of Chevron gas that has Techron as an additive.

  2. The tires are probably rock hard and dangerous. Too old.

  3. I have no faith in under body coatings. I feel that they merely trap moisture and enhance rust . But, I think roads are salted there. If an oily goop, not a tar cover, perhaps. On you tube, I have seen that. Oiled!!!


Check belts and hoses for sure. And see about a stakedown kit for the exhaust valves (not too expensive)

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Use 10/40 or 15/40, Gage - 10-30 is for very cold climate indeed…:slight_smile:

And don’t overdo the injector cleaner, it’s not engine candy - and some oil company already add a reasonable amount…

xj6 85 Sov Europe (UK/NZ)

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I’m with Carl on the underbody. Put it up on a hoist and have a really good poke around yourself. Patch repair with a can of stone chip where necessary. Proprietary rust proofing on an old car might mask a multitude of problems. Welcome, Paul.


And please read the recentish thread from a guy asking almost the same question :wink:

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Pictures, pictures, pictures please :blush:

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Some good info here:



Here she is!


Nice car!!

Preciate that Carl!

I grabbed the high mileage synthetic blend high mileage kind because, though it is relatively low mileage, one of the tanks is corroded (not using it anymore) so I wanted something that would help clean it out. Also I grabbed 10w-40 (not 10w-30 as I mistakenly said) due to the climate up here. We do get pretty cold in the winter. All that said, would you still recommend Castrol 20w-50 full oil instead?

I’d say that 10 40 is fine for your clime in winter. As I recall summer there is plenty hot. 20 50 then? I’ve been in NY twice in my life. Once in December, and the other time in June!!!

We are in our colder season low 50’s F. 20 50 is fine./ Here


I run 1040 in winter and 2050 in summer. Starts a little better on cold days.

Mine’s pretty much exactly the same as yours but probably a good bit rustier! I do like that color.


Warning, WARNING!

Do NOT use Ziebart aftermarket undercoating: ill-applied–and on old undercarriages, there is no easy way to not be ill-applied-- it can and most likely WILL cause long-term damage.


Welcome to the wonderful world of Jag ownership.
'85 nice! I have an 85 too.
I think 10-30 is a bit light for this engine. A buddy of mine, who built engines for Jaguar back in the day; and rebuilds Jaguar Engines as a business (now) uses 20w 50. I too run 20w 50 and in the winter I run 15w 40. These are old engines and the castings and milling machines were also old and worn, even at the time these cars where new. The B L (British Leland) had gasped it’s last breath; and became nationalized. Some how Jaguar sidestepped being dismantled unlike the other B L acquired labels, Triumph, Rover, Austin, MG, Morris, Wolseley, just to name a few. Anyway,

The machined tolerances back then weren’t anything like the engine tolerances today. I suppose that goes pretty much any American engine of that time too. Maybe because people were doing the machining instead of robots… idk just a hunch. The gaps were taken up with shims, and “thrust bearings” and as you dive deep into the mechanicals, especially the suspension, you’ll find a butt load of shims sprinkled in here and there. That being said,

I run a full synthetic in all of my XJ6’s. Redline 15w 40 in the winter and 20w 50 in the warmer months and WIX oil filters. My Series III’s are my daily drivers.
My XJS’s I run Amsoil 20/50 Z-ROD - mainly because I don’t drive them as much and the cars sit more than they probably should. Oil pressure is good in these engines 60 or 70 psi at 1,500rpm is how they left the factory.

Fuel Injector Cleaner?
Occasionally I’ll run either Royal Purple or Lucas. Is there a benefit? I’m not really sure.

The biggest issue with these cars is rust. well abuse & neglected maintenance…

Places to look and the most popular

  • Wheel arches
  • behind the “clean out” panel just behind the front tire,
  • the front and rear windscreens,
  • the Boot lid edges,
  • sunroof,
  • just behind the rear passenger door between the front of the rear wheel arch and the door opening,
  • passenger compartment floor boards mainly the drivers and passenger seats around the transmission tunnel,

Oil Leaks
My meager experience with oil leaks is pretty much just the top end, and the D plug on the back of the head between the cam cover and the head is usually the culprit. It’s rubber gets old and hard and leaks
A LOT. replace the gasket, make sure the camcovers mate the head well (enough for the paper gasket to take up the slack) replace the D plug(s). Then there’s the copper washers…
these washers are good for essentially one go, Then have to be replaced or annealed otherwise these will leak.
Rather than cranking on the cam cover nuts to make the leak stop, take the nuts off, check the camcover for any sign of deformity if all is good, then replace the copper washers before tightening to spec. These cam covers will deform if over tightened. Oh, and will continue to leak around the studs.
Another option is cupped neoprene stainless steel washers which is what I’ve got on my '86 XJ6 the PO went all gorilla on the cam covers and the only way I could stop the leak was stepping away from the copper :frowning_face:

Stake down kits…
Well. Necessary? not really. Then why? Stake down kits came into existence to keep the tappet “cup” from walking out of the head. The kits are cheap, and really only need to be installed (if at all) the exhaust side - where there’s most of the heat. These bits are an interference fit and rarely walk out of the hole. Causes are overheating and a really tired XK6. If your XJ6 has a good service history, then I probably wouldn’t install the stake down kit. I have 3 kits and haven’t installed them.

Get a manual
Perform a proper service. The Series III manual the abridged Green Bible as I call it (available on Amazon &, is a bit limp wristed for my liking. The Series I & II manuals are much more detailed, and a lot (not all) is relevant to the Series III. XK unlimited or now Moss - has a electronic manual that covers all of the Series 1-3. It’s good. Really good.

Keep the sunroof and petrol filler drains clear. I use stranded CAT5 ethernet cable with warm soapy water. Gently run the cable down the holes until the water drains out. the sunroof drains down the A and C pillars. The petrol drains down around the bottom of the petrol tanks.

Groit’s leather cleaner and conditioner is one that I’ve used. If the leather is really dry then I run off to the Tack shop (that horse saddle place) and get their saddle conditioner. Bickmore. This stuff is amazing. Lexol leather cleaner aka glycerin or any glycerin soap will take any oxidation off but it will also take the color along with it. So be careful.
the Groits products didn’t take the color or any oxidation off, but once you start using it, it’s something that will need to be applied regularly - like monthly if the car is in the sun. Not so much with the Bickmore products.

I’m not talking about prophylactic’s. EEEWWW!
Hoses and suspension rubber bushes and mounts.

If one is about to let go, then others aren’t too far behind. save your self the hastle of draining and burping the cooling system more than once - replace all of the coolant hoses at once - the water pump too if it shows any signs of leaking. Though - I haven’t had any issues with my water pumps on the XK6. Just the V12’s and the V8’s Go figure.

What gives the XJ6 it’s fabulous ride quality is the fact the suspension is for all intent and purpose fastened to the chassis by rubber & bolts. I’ve replaced with poly bushes and regretted it. Seriously regretted it. Any suspension point that is mounted to the chassis should stay rubber unless like to hear every plastic trim piece in the interior rattle. Granted poly bushes come in different hardnesses, but trying to find the right one for a Jag can be an exhausting search & really expensive.
rack bushes - poly; upper and lower control arm bushes - poly, swaybar mount - rubber, endlinks - poly

This is just an abbreviated list based on the trials and tribulations I’ve gone through with my less than perfect XJ6’s

I’m sure there’s more.

Welcome to the affliction


Mark Lee

Very nice summary!!

And your poly bush statements haunt me too but not on my 86. I have 75 BMW 2002 I restored and not knowing much 10 yrs ago I used hard poly motor mounts, tranny mount and steering column guibo.

Bucket of rattly bolts at times when motor is cold. Needless to say I have a set of the above in OEM BMW rubber and looking for time to replace

She should just hummm silently then :blush:


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As far as I am concerned, poly joints and other solid bushings should really only be for track use. They are just unsatisfactory on the street.

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Speaking broadly, I think at least some people (Jag owners or not) are drawn to the poly bushings because the rubber replacements commonly offered these days are so crummy. I hear stories, fairly often, of ridiculously low service life.

I’m not a fan of them for street cars either…at least not cars where NVH is a consideration


Yea, the apparent lack of reliable and authentic Metalastik mounts would be a consideration.

Years ago, I found a place that claims to reman them, as OE: that said, all I can recall is, it was, of all names, Steele Rubber.

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In most cases, I would agree. There are a few exceptions, though, the Jaguar steering rack mounts being one of them. I also don’t mind using poly on inner anti-sway bar bushings, although I generally prefer rubber at the end links.