Mileage comes from tuning and piping not the brand of motor. I can tune my +4C to get 15 minutes but why bother when the motors reliability just runs out the door. If you can get a motor to say 11 or 12 minutes with decent temps in my opinion it is right where it needs to be. If you can afford to replace motors every weekend(not me) then hell go for the gusto and get that 15 minutes out of it. I dont mean to flame but I just dont see the correlation between mileage and it defining a good motor. my limitted experience tells me most if not all in the .21 class are capable of the 8 to 10 minute range quite easily which is respectable.

The WERKS B6 is an interesting motor. I run with a pro that has one and is sponsored by them. Like any motor it has its perks and issues. Thats all I will say.