When I first started flying twins, I used a glo-driver thiinking I was really increasing reliability. After a really good engine guy tweaked my engines, he asked why I was using the glo-drivers. I told him I needed to insure maximum reliability. He asked if I used a glo driver on any of my single engine models. I told him no and he asked why I would use them on a twin. He went on to say that if the engine(s) are correctly set up, there should be no need for a glo-driver. Since then, I have concentrated on setting the engines up correctly and have never used a glo-driver since...never had an engine flame out either...of course, you could lose a plug but then a glo driver wouldn't help in that instance anyway