Joe, I haven't seen the need to change anything going from 10 to 15 percent. I do have to adjust the low end when going from 15% to 5% though. My YS 1.10s don't run well on the 20/20 fuel but my 1.20YS engines like the 20/20?? I figure it goes from engine to engine. All of my glow engines have to get the high end opened up when it goes from the 100s down into the 50s. Depending on the temp. drop. I have to open the high end one click at a time and then they are fine all winter long four clicks fat. This week it was in the mid 60s to about 70 and I had to lean the high ends two clicks. Two to go before it settles into spring here. Other then this major weather drop I don't touch my needles unless I change prop sizes.