Assembly/Engines

Having had my first race Im wondering how the Assembly works for the next race, specifically engines.

Ive got 10 engines with restock due in 18 races.

My question is if I choose to refit the current engine (currently at 85%) does that refurb the current engine
or does it fit a new engine?

If its the later can you refit the used engine at a later date or is that engine gone forever?

it replaces the engine.....you will only then have 9 engines left....

It is the latter, and the engine is gone forever.. :-)

Thanks for that :-)

what does the 1C, 1D model means?

1C is better or what?

The higher the letter, the better the part!
So 1D is better than 1C ;)

Great, tks!