Seems to me that the careful approach to Jaguar oil is simply to visit your Jaguar dealer and have him select and change the oil. EZ/PZ with virtually no risk.
On the other hand if you want to operate independently, then suggest you educate yourself; and a fine source for this is www.bobistheoilguy.com. Bob has a forum where you can argue all the merits, etc of any oil.

 

Only on a clear day, unobstructed by the gunsmoke.

 

As it is the weekend and I was bored I leafed through my Jaguar World, Jaguar Monthly, Jaguar Enthusiast and Jaguar Drivers club magazines that I have accrued over the last 20-30 years because there have been a number of articles on the XK, V12 and V8 engines in them. Many of them go in to great detail on how the engines came about, who was involved and their thought processes and they don’t tell the same story you do so I would be interested to know what your source is.

One area you might be confused in is the link with Standard. Standard provided the engines for the SS models and towards the end of the war Jaguar bought their tooling for the six cylinder engines. When production resumed in 1945 Standard still supplied the 1.5 (1.8L) and 2.5 (2.7L) and Jaguar built the 3.5, 6 cylinder models using the Standard tooling.

The XK seems to have been an in-house design and in fact the X stands for experimental and the K was just the next letter in the alphabet as they created their prototypes.

They ranged from the twin overhead camshaft 1360cc XF through the XG, which had opposed push rod valve operation with the camshaft in the block, to the 1996cc four- cylinder XJ-4 which was the first real prototype, incorporating all of the features that the design team had been seeking to use.

From this was developed the six-cylinder 3.2-litre XJ-6 motor, which didn't really produce the power sought, and eventually the final iteration, the 3442CC six, became known as the XK engine and the mainstay of the Jaguar operation. No mention of Standard anywhere.

The design team comprised of Walter Hassan, chief experimental engineer and design draughtsman Claude Baily who was assisted by a keen young draughtsman by the name of Tom Jones. The final key member of the team was a consultant called Harry Westlake, a freelance engineer specialising in cylinder head design and whose “expertise in gas flow was probably unmatched in the UK at the time”.

As for the V12, development of the original Jaguar V12 started in the early 50’s and was intended to succeed the XK engine in their Le Mans cars. The original designs were drawn up by Claude Baily but the imposition of a 3 litre maximum capacity at Le Mans put a hold on development. There was then talk of the limit being raised for prototype cars so work on them started again which culminated in a number of quad cam 5.0 litre engines, one of which was fitted in the XJ13.

Once it became clear that the quad cam engine was too heavy, bulky and impractical they looked at other options and that is where the V12 that was fitted in the later production cars came from.

There is a really interesting 8 page article in the July 1997 Jaguar World that goes in to great detail about the journey they went through when designing the V12 and that includes a lot about the various things that were tried along the way and the technical solutions.

There is mention of Coventry Climax, by then a subsidiary of Jaguar, but that is only in relation to the knowledge brought back from there by Walter Hassan of the flat head, OHC and bowl in piston design that they used on their industrial engines. So yes, there was some influence but it is very normal to draw on your previous experience when doing your job.

The name for the AJ-26 engine came from adding up the cylinders of the engines they experimented with before they came up with the final design (6 + 8 + 12) and while leafing through I found an article on the AJ-V8 and they appear to have been designed in house as well.

“But even as the 4.0 and 3.2 litre AJ6 units were being prepared it became clear that no development of this engine was ever going to match the Lexus LS 400's V8 in terms of refinement, not to mention packaging and other requirements for future models, so once again a Jaguar V8 became a serious proposition. Accordingly, a small team of engineers led by David Szczupak, by then manager of Jaguar's advanced power train group, began investigating the subject in 1989 at Whitley; this was under the direction of Trevor Crisp, overall head of the power train engineering.

With the V8 configuration confirmed, Szczupak and his team had the advantage of working from the proverbial clean sheet of paper; nothing was going to be inherited from previous engines, neither components or manufacturing tools. Early work involved single-cylinder experiments which played a key role in establishing early on the new engine's major characteristics, involving as they did almost every different combination of bore and stroke, porting, combustion chamber shape, valves and pistons. One unexpected result was that five valves per cylinder - which could theoretically be expected to improve combustion and performance – brought no benefits in practice compared to four valves - at least with the AJ26's exceptionally large inlet valves (1.374in diameter) in relation to the bore size.

The engine which gradually emerged was highly advanced in many areas. The cylinder block was a composite design which combined lightness with exceptional rigidity; in low pressure die-cast aluminium from Kolben-schmidt in Germany, it incorporated a cast centre diaphragm linking the two banks, while Nikasil plating of the bores eliminated the need for the usual cast-iron liners - at least, so it was thought!”

 

As a 3rd generation manufacturer since the 1800s, I spot something, its the thing that ultimately doomed my father's company. One is a prisoner to tooling. Its the reason Standard put in their own tooling. One only wonders what Jaguar would have been capable of if they could do what Standard did.

There is surprisingly no mention of Harry Mundy- he was the other half- who had perhaps the greatest racing pedigree- BRM, Lotus. Seen here explaining the v12 with Walter in the video below.

The ambiguity remains if Walter and Mundy had designed the engine a decade before Jaguar both the company they worked for??

 

Harry Mundy left Coventry Climax in 1955 to become Technical Editor at Autocar Magazine and was lured to Jaguar once they purchased Coventry Climax in 1963 to become chief of engine development.

The development of the original V12 (confusingly called XJ6 internally) was signed off by the Jaguar board in February 1962 and design work was 50% complete by the end of that year so he wouldn’t have had any input until later. The engineers listed as working on that prototype included Jim Eastick, Frank Philpott and George Buck.

There is no evidence in any of the articles I have read that he or Walter Hassan brought V12 engines under their arms from Coventry Climax and it appears that V8’s and 4 cylinder engines were the company’s speciality. I think they just brought the knowledge that they had picked up from their time there and used it to great effect at Jaguar. Their experience of light weight aluminium engines was actually based on the light weight fire pumps Coventry Climax used to make and that led on to racing engines for Le Mans, F1 and F2.

Bonus information:
The first V12, XJ6/1 first ran on 6th August 1964 and 8 ‘XJ6’ engines were built in total.

161,996 V12’s (XJ25) left the Radford engine plant between 1971 and 1997 which meant that I personally owned 0.00002469 percent of them (4)!

 

On the other hand, the OP has secured an answer to a question that many present and future DIY-type owners of this engine have been asking since it was first released.

"Which over-the-counter oils can be used other than the dealer only types that they frequently cannot or will not sell to the public?"

For that we owe him a big thanks!

 

We are in agreement then, in my eyes.

Jaguar made its first engine when it bought an engine manufacturer.
Jaguar made its second engine when 3 engineers came over from Lotus. with plans hatched there.

My claim is that the third was the most independent effort, just not financially.

 

That isn't what I think at all, especially once I had read all of the articles, but it seems to be what you want to believe so I will leave you to it.