Well, you must have different oil: when it’s -10C, here, I can damn sure tell the difference in how Margaret cranks.
You’ll also recall the times, in the winter, I reported -20C to -25C: at those temps, 20W50 becomes peanut butter.
It does get quite viscous in the winter. Again, there is a slight difference but it’s not stalling at all. Maybe a battery difference too?
Sigh… precisely where did I ever mention, “stalling?”
Higher viscosity oils, even multi-vis ones, are recommended for certain temp ranges: at best, 20W50 is less than optimal at -10C, and below.
As shown, yes, it can be used down to -18C: on Tweety, doing that would result in oil pressures–on a mechanical gauge–of near 100 psi. That is not good on many levels.
Did I say you said it was stalling? I said nowhere near stalling after a night out below -10C. Call it labouring if that’s better. I‘m not arguing with you nor do I want to, just writing down my experience. I don’t have to do that I guess, sigh. The XJ has a larger bypass - maybe - not that I know for sure.
Wow. I’m sure it starts great, but with oil that light I’d worry about it after it warms up. Full synthetic 5W-50 sounds like a much better idea to me.
That’s in his modern car and if diesel does the job…
We all know new cars run on almost water and do so forever. Not so great in our Jaguars. Thicker when cold means less leakage in my mind and limited experience.
Or was it meant to say Ow!…20?
If it leaks, fix the leaks. The real concern of oil weight is the design of the bearing shells, tappets, etc. Yes, modern cars run on thin oil for 200K miles, but they were designed to do so. Our old Jags were designed to run on something closer to Bunker C.
I say limited because the leaks stopped once I filled in 20W50 and before that, it was bad. 15W40 and thinned down a great deal I believe. Oil pressure went up a little which was then good at hot idle. I never went back to thinner oil besides a long trip (1200 miles) that necessitated gallons of Tesco‘s finest 15W40 and yes it did leak again until I changed the oil. I wouldn’t believe the story if it wasn’t mine but that‘s what it was, and sure, it might be related to long trips and/ or ten years of standing.
Fix the leaks is so easy until the sump is involved… so I was happy.
I wouldn’t: many new cars do fine on it, and the Hyundai is still ticking along great, at 256,000 miles.
Lubricity and flow. Two key words. In the spring, I switch to 20W50.
……….On the hyundai?!
Yes: it gets enough use to justify seasonal changes.
On the Rover and the Jag, I only change them in the spring.
Yes but isn’t that unnecessarily thick? I have a 5W and it sees lots of Autobahn. Supercharged too. No issues at all…
The car consumes some oil: the heavier viscosity slows that down.
You run a Hyundai on 20W-50? That can’t be advisable, can it?
Again… 256,000 miles.
Why would it not be?
Ah it loses oil. While brand new 
I use Penrite 20w60 like Paul. 25~29 AUD for 6 litres when on sale.
The engine runs quieter and leaks less. It is recommended to me by a well known local Jag engine rebuilder.
In general, oil that’s too thick can be as bad or worse than oil that’s too thin. In the worst case, it can result in reduced flow to the bearing shells and more being bypassed directly back into the sump. Bearings overheat when the oil flow is lacking.
Obviously, it hasn’t hurt the Hyundai any. Those wily Koreans probably designed it to run on anything from olive oil to Bunker C.
BTW, is this the same car you tried to start with a solid block of ice under the hood?
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20W50, on an old engine, in hot summer temps, is not too thick.
Some newer cars use pretty tight tolerances, and require thinner oils.
Not quite a 'solid block of ice: it was snow-packed… and that would not have been an issue (it’s happened a number of times), but the damaged lower timing belt case was.
I’m with Paul and Mr. FP. I use Penrite HPR 30 in my lump but also in the past in Merc sixes, one doing over 400k. I also know of a country XJS V12 that was recently sold with over 700,000 klm that had HPR 30 from new. At the 700k the engine had not been touched. All anecdotal I know but qualified nonetheless. You can do a lot worse than using HPR 30.