It's not quite fair to compare project day rates vs straight salary but I know one Lead/Principal control system engineer who worked on FPSOs. Pre-2014, he was

It's not quite fair to compare project day rates vs straight salary but I know one Lead/Principal control system engineer who worked on FPSOs. Pre-2014, he was making 90k a month when he was offshore. His offshore day rate was significantly higher than his onshore rate. Lots of travelling to and from manufacturers doing factory acceptance tests for equipment packages that go on the ships. You then live near the shipyard (Korea, Singapore, Brazil, Vietnam, etc.) while the FPSO is being built. You then leave with the ship and start commissioning everything. All of the other guys I know on offshore rigs don't make as much as the example above but they'd be over 200-300k out of Houston or elsewhere on the gulf coast.