Only when it's new and normally a midgrade 21 or larger, or a really high grade 12-18. Back the glow plug off 1/4 turn and fire it up. Set the trim on your remote to where it's almost revving enough to make the clutch kick in, then tighten the glowplug back down. You should only have to do this for new engines that you are breaking in.
What engine and what fuel are you running? Also, is the engine new or old?