Dhc8-Q400- SAS do not have the Drop down O2 system, some authorities allow FL270 not FL250.
The Q400 at ISA temp will cruise at 340-350TAS (235KIAS) and MRC with about 550kg/h but you can get under 400kg/h with slightly reduced cruise of 210ktsKIAS which makes it far more economical for a 2-3 minute penalty on 1 hour sectors. With a large flat rating on the engines it also climbs like the proverbial home sick angel up to FL250 which makes it virtually unique in 70-75 seat class turboprops.
Plus it can descend in TMA airspace at 270kts KIAS once below FL200 makes it fit in more in terminal areas with the big boys. Priceless at CDG!
Reckon real world on 900-1000kg total for a 1 hour sector with 56 minute airborne times.
Can't comment on ATR or Q300.