Hi I am in Europe and need to change oil on 700 SCi,
the recommended from Merc is GT-1™ High Performance Motor Oil 20W50.
1Q: is that a synthetic oil?
2Q: can that oil be substituted for any 20W50?

Kendall GT-1 is a quality, conventional oil. It is not a synthetic. Other quality 20W50's would include Valvoline Racing 20W50, Castrol 20W50.

You can substitute any 20w-50 with either any other 20w-50 or 15w-50. As long as the oil meets or exceed the specification recommended.

Merc most likely wants a 20W-50 with high ZDDP such as Kendall GT-1 which is similiar to Valvoline VR-1.

GT-1 has the following specs..fyi..

a cst @40*C of 175

a cst @ 100*C of 18.5

VI 120

Phos/Zinc 1100 ppm/1100 ppm

TBN 7.8


FYI..these specs are near equal to Mobil-1 15W-50 should you decide to go with a synthetic.

thanks to all