Interesting video regarding oil in modern engines

A bit above my pay grade, but still

Old guys like me always increased viscosity with older engines because of the bearing wear, and a higher Bearing Load Thickness would always help. That was also a reason for High Volume Oil Pumps, to increase the amount of lubrication to the bearings.
Totally makes sense.
BUT, the thinner 0w20 for Jag engines is to ensure the flow rate to the timing chain tensioners. Bearing Load had no involvement in that decision. I don't know the volume of the Jag oil pump, but it must be suitable. The tensioners probably were designed with a slightly inadequate flow passage for tensioning those tensioners, hence the presumed failures.
Me, I'm between.... sticking with 10W20 or 10W30, dependent on other factors. Higher heat is an enemy of thinner oils. I do live in a desert...

@Cee Jay How long have you been using 10W20/30 in the 5.0 litre? Aren't you one of the rare examples with the original chains/tensioners on a 2010 and no issues?

Out of the last 12 years or so, I've used 0W20 (or 30, can't remember which) only once or twice, the rest has been 10W stuff. No tensioner problems in 72,000 miles. Still original water pump too, so I dunno wassup. The only semi-major thing was an injector five or six years ago. Oh, and one cat is low performance now also. Still flows fine though.

Apparently, the internet myth which this recall busts is that you cannot use higher viscosity oil at the "summer" end than that recommended by the manufacturer.

This is a bit strange for me to hear as for the last 40 years I've always been very happy to use an oil which is lower viscosity at the "winter" end and/or an oil which is higher viscosity at the "summer" end but not the opposite, and have often done so, but not the reverse. As a chemist/physicist, I worked out for myself why this was the case but I guess that anyone can do it if they use a bit of logical thinking and understand the viscosity/temperature relationship. I had no idea that I was busting any myths.

Richard

After watching all the you tubes of the Range Rover 5.0s with timing chain issues, I too have been concerned about the oil viscosity discussion. My last oil change at Jaguar( awhile ago ) had Jaguar using 5W-20. I live in Florida. My very last oil change ( first oil change by independent shop ) we used Castro Edge 5W-20. At 18,000 miles I’m usually more focused on the coolant level ( every plastic coolant part has been replaced ) than my timing chain.

What I’d always understood was that with multi-weight oils, the low (thin) number characterized the oil viscosity when cold (startup), and the big number was the weight at operating temps— so once the engine was at operating temp the low number really didn’t matter. And with the 5.0 the switch from 5-20 to 0-20 was to ensure that the oil was really flowing through those narrow passageways right at startup.
not true? Always willing to learn something new.

So, one more oil topic

Decoding the 0W-20 marking:
0W — indicates the viscosity of the oil at low temperatures, where "W" means winter. 0W class motor oils ensure safe engine starting at temperatures down to -35 degrees Celsius. 1
20 — indicates the viscosity of the oil at operating temperature. For viscosity class "20", this is from 6.5 to 9.3 centistokes kinematic viscosity and from 2.6 to 2.9 mPa*s dynamic viscosity HTHS. 1

Decoding the 5W-20 marking:
5W — the number before the letter "W" (Winter) shows how much the oil can maintain fluidity at low temperatures. In this case, 5W means that the oil maintains fluidity down to -30°C. 2
20 — the number after "W" indicates the viscosity of the oil at operating, that is, high, temperatures. Viscosity 20 indicates that the oil will be very light and fluid at the engine operating temperature. 2

Thus, 0W-20 and 5W-20 oils have the same high-temperature viscosity class, which means that in a warm engine they have the same viscosity, but 0W-20 oil has an advantage, since its low-temperature properties are much better

There are specific temperatures/ranges for each end of the scale and the numbers are on different scales but, in essence, that's correct and illustrates why you can go a grade or two thinner than recommended at the Winter end and thicker than recommended at the Summer end. An oil which is 5W viscosity at 0C will thin down to 0W as soon as it warms up a little so a 0W is is not going to do any harm as the engine is running on 0W very soon after starting. Similarly, an oil which is at running at 20 viscosity at 100C was safely pumping round at 30 viscosity a short time before.

Richard

Well, I just ordered an oil change kit from Blauparts with 5W20 Ravenol…I hope my motor doesn’t blow up.

My 2007 4.2L has the recommended oil being 5W30. I am running 10W30 all year now. It could be smarter to use 5W40 here, where it can often be -10F.

All be aware..... The original "recommendation" from Jaguar was from fifteen years ago. New, even cheap oil is MUCH BETTER than oil was a decade and a half ago. Plus, your engines are now worn, the thinnest oils will not hold itself on all the bearing surfaces the way it did with zero revolutions.

100% this

Yep. I still use the same weighted oil as JLR originally recommended but have moved on to high mileage variety.

Nine years ago I switched to 0W-40 in my 4.2L, as it is listed in the manual as acceptable and has a wider temperature service range than the standard 5W-30. A year and a half later the car leaked over the winter from the left valve cover. In replacing the cover seals I found that one of the cover bolts was loose and was the likely source of the leak.
Fast forward five years and I had another leak over the winter. No source was obvious, so I added green fluorescent dye during the oil change. The next spring there was a small leak, but everything (including dry black plastic parts) looked green under the UV light.
Trying another tact, I switched to the standard 5W-30 oil (high mileage) and added orange fluorescent dye last year. This spring I found the car dry underneath, no leakage, no orange fluorescence under UV light.
So sticking to the standard 5W-30 (with orange dye) for now, and hoping for no more winter leakage.

The USAF used JP4 jet fuel for the longest time, then there was a switch to JP5 (in the 1990s??) because the flashpoint was higher and less vulnerable to static ignition. Thing was though, JP5 was 10% thinner than JP4 so half or more of the jets started having fuel leaks.

2007 XK manual

Also from the manual.