Engine boss Andy Cowell is leaving Mercedes' F1 team next month.
Instead, he will "consult to Mercedes-Benz AG on a major future project" until 2021, and be replaced by "internal appointments", the reigning world champions said.
"Now is the right time to move on from my role and seek a new engineering business challenge," said Cowell, who joined Mercedes-Ilmor to work on the V10 engine in 2004.