I'm ready to do my first oil change on my '97 x300, 4.0L. When I got it during the winter I went to a Valvoline place because I don't have a garage and it was cold. They put in 5W30.
I live in southern Connecticut so it can get close to 0F/-17C. And during the summer it gets to above 90F/32C occasionally. I looked at the chart and I was thinking about going with 5W40. Any thoughts?

 

I'm assuming you have the upgraded timing chain tensioner with the large cast arrow

If not , determines oil viscosity target to reduce start up until pumped up noise

Illustration 2

03-1-09 Rattle After Start.pdf (jagrepair.com)

 

I do have the upgraded chain tensioner.

 

When I worked at the dealer when these cars were in factory warranty, we used Mobil 15W40 for all L6 and V12 Jaguars.

You might want to switch from 5W to 10W if oil consumption is apparent.