Change from mineral to syntetic oil

Hi Friends,
Yesterday i made my last trip (before the idiots here in belgium will put tons of salt on the roads and change belgium in the Bonneville salt flats)
It was cold: 2°C and my mineral oil don't warm-up, even after 100 kms my oil pressure was still 60 PSI at 4.000 rpm
So i wish to swift to multigrade full syntetic oil, my mineral was 40 monograte
My engine was rebuild only a few thousend kms from now, can I do the change safe??
Wondering if some one did it??
Cheers yves

Your concern has to be rings being seated yet, with some 1500 miles on since the rebuild.
Others here may disagree, but if it was my bike, I would switch now to a synthetic like 15 or 20-50.

I like Redine 20W50 Motorcycle Oil. It has more zinc than the car oils and has moly that the strictly motorcycle oils don't due to the potential for clutch slip. It's marketed for big twins that have separate primaries like ours. They also have an assembly lube and a break-in additive that is a zinc prep to protect the lifters. I don't get the dino/synthetic during break-in debate. Syntheic isn't any more slippery than dino.
There's trolling, then there's chumming 8) What can I say, the weather's lousy, can't ride.

Once the rings are seated I can see no reason not to switch to a synthetic.