Hey all!

My name's Will and I've just bought myself a 1985 XJ6 Sovereign.

I need some advice on which engine oil would be best for it. I began looking at oils like Castrol GTX2 20W50 or Mobil Super 1000 20W50, thinking that the higher viscosity oils are best. I went to Shell's lube match website and they've recommended their Helix Ultra 5W40! So I'm a bit confused!

Wouldn't running a lower viscosity oil damage the engine because of it's age? Plus there's the whole synthetic vs non-synthetic debate.

What oil's does everyone here use and why?

 

Most 4.2 owners like 20/50. Some use 10/40. The manual suggests anything from 5/30 to 20/50 depending on ambient temperatures

I don't think there is a bad oil out there and the old 4.2 certainly doesn't require anything special.

My idea of "best" is whatever name brand is on sale that day. :-) In years gone by I always used Castrol because Castrol and old Jags just seem to go together....some sort of tradition that I cannot longer afford to play a part in keeping alive.

There are all sorts of special oils out there, including synthetics. If you wanna treat your Jag to something special for the feel good factor ( a notion that I fully appreciate, beleive me) then by all means do so. The engine, though, doesn't really care.

If your engine is gonna be exposed to extreme heat....like high-tailing it from Dallas to Las Vegas at 80 mph in August, a synthetic would probably offer more protection.

Others will chime in.

Cheers
DD

 

My take on this is that the XK engine you have dates from 1947 and your engine was actually made on the machinery installed to make it that year, and this machinery was secondhand !!.

These engines are not made to the degree of precision that the later engines are. I would keep to the original Jaguar oils recommendation (if you have it). Certainly good 'ole 20/50 will be perfectly OK, but I would worry a bit about 5W/30, but 10W40 will probably be alright. With the very light viscosities you might not be able to keep the oil pressure up to spec. due to wider bearing clearances. For instance at the top end, Jaguar never seemed able to make their minds up about an oil supply to each cam lobe. The cams are drilled to make an oil way to supply the camshaft bearings. Some engines had a drilling on the base circle to directly supply, then that was given up and splash was relied on. I suppose it was a toss-up between starving the bearings and starving the cams ! My own 4.2 cams had no cam lobe drillings and I found the engine rather "clattery" when cold, although there were no other ill effects.

 

Thanks for the advice. I'll try Castrol 20W50 for now.

Doug, I actually found that Castrol sells classic engine oils! See this website. http://www.castrol.com/castrol/secti...tentId=7027099 . I'm not too sure how much a can costs, but it's probably really expensive!

Fraser, you seem to know a lot about the XK & XJ engines! https://www.jaguarforums.com/forum/s...ad.php?t=32768
What sort of Jag do you own? My engine block is the 8L, so I assume that this is the final version of the XK/XJ engine. It sounds epic!

 

Hi Beast

Yes, I do know a fair amount about the old Jaguar straight six engine, (called the XK engine by the way). I rebuilt a Mark 2 of 1968 which had the 2.4 short block engine, then I had an XJ6 4.2 for 14 years, and rebuilt that engine around a replacement block.

If you have got the 8L block, have you had the head off ? If you have, can you tell me if the block has "slots" between the bores ? If your engine has these slots it will be less prone to head gasket failure, but be aware this can still occur. These slots were the last mod done to these engines before the aluminium block engine came out. The XK engines usually need an overhaul before 100k miles is up. If this is done, they will be OK for another 100k, they are very repairable and maintainable.

The rear main oil seal can be an absolute pain for leaking oil onto your driveway, but it doesn't actually do any damage, it's just a nuisance.

Remember the basis for this engine is a pre-war block design, with overhead cams in an alluminium head as an add-on.

 

Hi Fraser

The XJ6 is still very new to me. When the time comes for an overhaul, I'll let you know if there are slots between the bores (Lets hope they do!). The XJ has been owned by a mechanic. It's been well-maintained, but rarely used.

Do you still own the Mark 2? If so, do you have any posts about it? I reckon the Mk2 is awesome!

Will

 

Hi Beast

I only have the pictures of my Mark 2. I sold it in 1988 to finance IVF which ended up with the arrival of a lovely daughter in 1990. However she came home from the hospital maternity ward in a Jaguar, a 1980 XJ6 4.2 I had this from 1988 to 2002. Worst built car ever !! Good design though, and everything is DIY repairable, except for the various mods made over the years to the engine to keep the power coming, but which badly affected reliability.