Agreed, it's a poor document at best.

The DS420 was mainly sold to funeral directors, and around 95% of them were sold in the UK market. Given the relatively mild climate in the UK, perhaps they were not too fussed about getting the temperature ranges right? I can only guess.

After the UK, most of the rest were sold in Continental Europe until the late 80's when a significant number of exports were to Japan. That is where I bought my car, although it was built to French specification and sold in Paris. I'm sure that was a dealer of convenience, as 2 months after delivery to Paris the car was registered in Tokyo.

 

I think they are shockingly poor documents. The only sensible documents regarding Engine oil recommendations came from the Monograde era to my mind. I think most oil company people would agree. i.e. from the William Heynes era (up to '69 IIRC). I think they allowed viscosity to increase to make up for poor tolerances.

All Jaguars in SA have a very poor reputation. They are a hard sell to this day. This in a market where in the 60's, 70's & early 80's saw the Chrysler Valiant as the best selling vehicle on the market by a large margin. (Locally assembled and bodied ~ all bodies locally pressed by Steelmobile & precise). Now it's the German big 3 and Toyota with Ford making some inroads.

Only when I restored my S type did I understand that they were very well engineered vehicles that were generally very badly built. The worst of the build in the late 60's to most XJ6's they sucked. The CKD vehicles sent here once we dropped the local content weight measure & moved to value, had our build force shaking their heads and saying how are we going to assemble this rubbish. Every trick in the book was required to assemble them. Nothing fitted. I guess the Trade Unions did not make life any easier.

 

Another item from JB's last document: it indicates either automatic transmission fluid for the power steering. As it's a Marles Adwest Varamtic, shouldn't it actually be the type F or type G rather than Dexron?

 

Yes! For longevity.

 

I'm not sure what the steering box is. The pump is a typical GM pump used in millions of USA built cars, so I'm using Dexron in mine. The spec from the 1989 owners manual says Dexron II D or Type G. Mind you, it also says GL4 in the manual gearbox, and none of the cars were ever built with a manual gearbox, so all of these recommendations need to be taken with a pile of salt.

 

Fluid meeting Ford spec M2C33 F or G gives far greater protection than Dexron II. It was formulated to hold together a particularly weak Ford Auto transmission. It is all I will put in my car. We also make a PAS Fluid that looks very similar. A few minor tweeks that are of little importance here.

I also think we can all agree that putting SAE 20W-50 in a healthy XK engine will accelerate cold start wear unless you are in the Sahara Desert at midday on a hot day. Not a wise choice.

 

Back when I had a 3.8 E Type, I used 20W-50, as it was the "done thing". The engine was also worn out, I first put in 10W-30 and I used a litre of oil every 80 miles. When I switched to 20W-50 that went up to a litre every 400 miles. However, when fall was coming and the temperature dropped to 10°C in my garage it would crank so slowly that starting was iffy. To combat that, I plugged it in an hour before I wanted to go anywhere and the car would start much faster.

 

Thanks JB ~ an excellent demonstration of oil flow cold & it's consequences
Note Canadian cars were fitted with Block cooling system heaters which changed position over the years which is not relevant here ~ also note I said healthy XK engines. Once worn & out of tolerance any old goo will do. You are just delaying the inevitable rebuild. Note Jaguars comments on "worn engines requiring overhaul" & SAE 10W-30's "compensated by advantages gained" further back in this thread.