That's ambient temperature, which is basically relevant for the initial starting "cold" engine temperature and ergo oil temperature. So like you said, really only the initial starting matters if you live at an extreme of the ranges like Alaska or Death Valley. Like you, I'm covered by all of those viscosities and 5W30 serves me fine for my West Michigan climate.

 

When it is -35°C, the convertible is staying in the garage and I'm staying by the fire. Don't really care about the oil viscosity at that point.

 

This is the LAST THING that you should be worried about to get changed by a dealer when it comes to changing the oil on a 2007 unless this your very 1st car and think just because of the brand and how expensive this car was when it 1st came out,you thinking it's difficult and should be handled by professionals at the dealership or else this is a very pointless question that makes me sort of cringe reading this if you have had experience with other cars before.To really answer your question,I use to get WAL-MART to do oil changes on my 2007 XKR back when i had 1.Also the 3rd generation Jags are easier to do an oil change on than most cars of the same year from earlier decades.But the fluid changes you should be worrying about like the rest of us, is what shops can change the tranny fluids,differential fluids,and supercharger fluids??????Those are the serious main questions that every Jaguar owner needs answers to right there

 

I changed the oil in my 2011 XK convertible today, using a kit that included 8 liters of Ravenol 5w20 and a Mahle filter. I have a vacuum extractor and the special wrench for the oil filter housing, and the whole thing took about 15 minutes. I only had to try seven or eight times to reset the service indicator. So far, the Earth seems to be continuing to rotate as usual. 😏