within 75% rated output

09:16 Jul 11, 2014 

"keep it at around 75% of rated output"? Like 75% +/- few %?

Quite a difference from "between 0 and 75%" / "anywhere less than 75%" - which wouldn't be doing any good to a diesel engine...

This looks like a case where few words can have serious impact - worth checking.

18:09 Jul 10, 2014 

Exactly!

18:07 Jul 10, 2014 

la plage de fonctionnement optimale d'un moteur diesel c'est entre 70% et 90% de la puissance nominale du moteur..

17:15 Jul 10, 2014 

Your source text seems to be poorly-written, and as a result, is ambiguous!

I think they did indeed intend to say "...at not more than 75% output"; however, that isn't actually what the text says! The ill-advised use of 'within' here actually tends to suggest that it should be operated at no less than 75%!

I don't think for one moment this is likely, but you do just need to be aware of that faint possibility; can you get any clues from the rest of your text? I'd say that if the rest of the text isn't brilliantly written, maybe by a foreigner, then one can assume it does mean what we've all supposed. However, if you know the true provenance of the text, and it was written by a reliable native speaker, then it might just be a good idea to check with the customer, just to be on the safe side.