All of this, always cold in this hot country.Should be OK then. You can just pretend it's an unseasonably cold day in a hotter country.
It says 20w/50 is suitable for use in the TD5 at temperatures above freezing.
I honestly don't know but I bet someone on here will have the experience to answer, these days I try to stick with 100% synthetic oils I think they have made giant leaps in the technology, probably helps modern engines doing massive mileage,
I'm old enough to remember engines that were knackered at 60k and needed things like decokes and bottom end re builds