The S90 is based on the same platform as the XC90 and will utilize the same engine range. (automobilemag.com)
But it's almost certain to use the same engine range as the saloon car — 161bhp and 188bhp 2.2 - litre plus 237bhp and 271bhp 3.0 - litre diesels, and a 380bhp 5.0 - litre V8 petrol — to drive its rear wheels. (evo.co.uk)
The Coupe has the same engine range as the standard GLC, so there's 220 d, 250 d and 350 d diesels, plus the powerful AMG 43 petrol. (autoexpress.co.uk)