Talk:McLaren MP4-X Championship/@comment-33869270-20181231023341/@comment-32545704-20190101004427

This page might also help

https://rr3.wikia.com/wiki/RR3_Wiki:Upgrades_Section_McLAREN#McLAREN_MP4-X

Looks like your best option is still to upgrade to Engine 7. It's only one more gold upgrade followed by 3 R$ upgrades. The other options are similar gold price and only give one upgrade each.