Synthetic oil for I-5s

[David]

I've been running 20W50 dino oil in my CGT and doing MMO treatments before oil changes. I was thinking of switching to synthetic for it's cleaning properties and to help keep oil temps down (in high speed/agressive driving on the highway my oil temp goes as high as 150*C, cruising is around 130*C and in town around 90-100*C). I realize there is a chance that the synthetic will clean out the engine so well that it will begin to leak or burn oil. My plan was to switch to synthetic for 6 months or so to clean it out then switch back if it leaks or consumes oil. So, what are your thoughts on this? What weight is appropriate for I5s? Is it available in 20W50? Do I even need it that thick with synthetic?

Dave
2002 Jetta 1.8T (hers)
1993 RX-7 R1 (weekend play toy, soon to be for sale)
1987 CGT Special Build 2.3
in SE Virginia