I've been running saitos for years and have had only minor problems running them. I've been very happy with the brand. Anyway, I've run cool power 15% for ever in my 150s and 180s and I bought some hobbytown 15% fuel made by wildcat. I always have my motors on the rich side so I don't do much adjusting of the needle valve unless the weather really changes. Anyway, first flight with the new fuel and 5 minutes into the flight, deadstick. Bring it back to the pits, start it up and now it dies at full throttle. Backed it off a full turn until it was running rich again. Flew a few more flights no problem. Finished up that gallon, went back to the cool power. I needed to turn the needle in a full turn. Later, opened a new bottle of the hobbytown. Turned out the needle full turn and flew a flight. Turned it in 1/4 for the next flight and had another deadstick. Anyway, I guess what I learned is that not all fuel is equal. You may have a problem with the motor but 4 strokes tend to just stop if they're too lean where as a two stroke changes pitch when it's too lean and then freeze up and quit if you don't recognize the warning sound. Especially when you pull to vertical. 4 strokes by the way can go very lean when pulling vertical. Did your motor die while climbing? The only way to really now what a 4 stroke is doing is to use a tach. However, I found with my new fuel that my range of adjustment on the ground was broader than with my usual fuel. Although it didn't appear to me or by my tach to be lean on the ground, it was leaning out enough in the air to cause it to stop with the different brand of fuel.