1 bar is still fine, as long as it goes up upon using the throttle. How long have you had the car?

I find that my oil pressure responds to temperature and humidity differently..i.e., the lowest I've seen it go was always on very humid, rainy days. Not sure why...

10w40 is fine for warm weather, but you can also try 15w-40. Going synthetic shouldn't make much difference, but with a synth 5w-40 you might actually see the oil pressure go down even more, just becasue it flows better.

__________________
Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k