Until recently I have used sidewinder 25% but in an attempt to solve this problem I have tried to switch brand. I went for the recommendation of RB's own fuel (also 25%). This posponed the wear of the glowplug slightly but nothing that's acceptable. A 30% blend has crossed my mind but according to most sources this will only make the engine even harder to tune - however this might end up as a last desperate attempt before I sack the engine.