How long would that be true if these (or any similar) engines began to be prolific?
Sadly as mentioned above it isn't really true. Whilst in the UK the self declaration thing may not be strictly observed by some, in Europe the policy seems to be more charge first ask later. Add mineral oil tax etc and you're in to serious expense. Still not as bad as 100ll though!
In saying that as Peter says 18 per hour for 240hp seems fine. But if that's in the cruise as the guy said it will be 30gph or so at msl.
Could be an excellent unit for the right aircraft.