You get a 10 place penalty for the first change, and then I think it is a subsequent 5 place drop for each component after the first. Alonso and Button this year have been constantly replacing engines, last season was even worse! Rosberg won't yet as he still has one penalty free engine that can have tokens applied, if he took free ones now, not only would he drop back but the amount of 'engines' unlocked would be the same spec as Hamilton's rather than a free upgraded engine later; Hamilton has no choice but rosberg is better off waiting before utilising the free engine with the upgrades.
4 engines would be too hard, after FP3 the cars in are in Parc Ferme and cannot be worked on so a 4th engine could not be fitted and still hit qualifying; I'd imagine the stewards would take a dim view of missing out on qualifying to install a new engine and then you still need to run it and test it which would be difficult in Qualifying.


