Just wanted to ask a few questions on glow plugs. Will replacing the old ones with new help the starting on 0 digit mornings or not? Also, do you need to replace the relay at the same time or not? I noticed some that were called fast glow plugs. Is there any difference there on them? Just wanted to get some feed back before purchasing and changing. I am starting ok in warmer weather, but it seems a little more difficult in very cold temperatures.