My Dodge/Cummins is interesting. While it DEFINITELY starts better at below maybe 50 or so, it will start with maybe just a bit more cranking than w/o the glow cycle. I try to remember but it doesn't seem very fussy about it. Above 55 or so it starts the same with or without a glow. I've NEVER used starter fluid.

The Mercedes in Mutt, on the other hand, wants glowed pretty much every time I crank it, even if it's warmed up. Not sure what's up with that. It'll be interesting to see what happens with the new pump.

My buddy's 7.3 Ford/Navistar is like Mutt - needs a glow pretty much every time. I suspect it's a characteristic of that combustion chamber design but I'm guessing.

Dan