what is the latest OS X i can install on a intel core duo 2.66 ghz machine, 8 gb of ram?

Oh wait Intel CORE DUO machines can't go further than OS X 10.7.5 (Lion). Please just specify your device

Most Core 2 Duo machines run to OS X 10.11.6 (El Capitan) however you'll have to specify the device as some Core 2 Duo machines can run up to macOS 10.13.6 (High Sierra).