[spike]

do you have a pop up spolier or fixed one?

if a pop one, probably why it is set for 75mph.

Is down to create streamlined/less drag during acceleration, and up at high speed to give downforce

 

[spike]

I doubt it would make much difference to fuel economy, if up.

However, in my mind it is seriously uncool to manually raise it when at low speed lol

I do love the way it pops up, by itself