Maximum allowable oil consumption for Lycoming engines:
Originally Posted by Lycoming Manuals
The maximum allowable oil consumption limits for all Textron Lycoming aircraft engines can be determined by using the following formula:
.006 x BHP x 4 ÷ 7.4 = Qt./Hr.
The clipper is rated at 245BHP, so according to this formula your limit is 0.8qt/hr.
1qt every 1.5hrs is very close to that - have you talked to the owner and the engineers? Anything over 1qt / 3hours is unusual, I wouldn't fly it if it goes through twice that....
Regarding the floats: The Robinson Fixed floats have a VNE of 110kts if I'm not mistaken (don't quote me). Your floats might be a different make. In any case, there should be a supplement in the flight manual that tells you exactly what your limit is. If the flight manual doesn't match the placards, something fishy is going on.