well i havnt ran a lot of glow plugs in my .21 engines but here we go.

1. odonnell #100 meduim plug it gives you great idle but does like a too rich of a bottom end setting so they wont last long doing that but they are the cheapest plug around there is a reason for that


2. novarossi plugs ive ran the #5 and #6 plug and i liked the #5 plug which is a med hot plug they last pretty long for me thoughout break in and about 1 gallon and never had random flameouts. they are kind of pricey.



i live in pa so i been using the odonnell #100 plug during the summer when its around 90+ with high humity.