I have a Grant Vortex Blue 26kw external oil boiler, installed less than 12 months ago. It's had intermittent non-starting problems resulting in multiple warranty visits, part replacements and eventually burner replacement. The replaced burner I discovered was a 'yellow flame' one, apparently the same as on the Grant Vortex Pro model. Having questioned this with Grant, I've been told that this is as efficient and my longer warranty is preserved but offered to either keep this one with a cash adjustment or have it replaced again with a 'blue flame' one as originally fitted. I'm concerned about having a hybrid boiler but the yellow flame's ability to burn biofuel might be an advantage in the future. Any thoughs or advice would be appreciated.