Best not to use glow plugs once car is warm?
 

I briefly read a response to an unrelated post the other day, where someone wrote you don't need to use the glow plugs once the car is warmed up and run after the initial start. If that's true, it'd be best I don't use them, as I guess they wear out after a while. I'm in Atlanta, it doesn't get that cold here anyways, but I guess the less I use the glow plugs, the longer they'll last.

What's your take on this?

Jeff 1991, 300d 118k

whats your definition of warm? Warm due to higher outside temps, or warm due to operation of the engine?

A few days ago when it was about 80 degrees here in the afternoon, my glow light didn't even come on. The car started right up.

I wait a few seconds when the engine is warm, ambient temperature probably doesn't mater very much once the engine is up to temperature. I doubt using shorter glow cycles will extend the life very much, but it might help a little.

Glow plugs are cheaper than starters. And easier to replace.

Once the engine is up to it's 80-85*c operating temperature the glowplugs are unnecessary for starting. It still won't hurt to use them if you feel like it.

I have been experimenting with this recently since I traditionally always waited until the glow light went out. I'm finding that once the engine is at operating temperature and I only shut it off for a short period of time, the engine fires up immediately without waiting for the glowlight. If the engine is slightly warm, and I do the same thing, it takes an extra revolution or two before it fires up. With a little practice, I'll know when using the glowplugs will reduce starter strain of about 2 seconds when the engine is not quite hot enough.

My owner's manual agrees with FI.

a 1991? Doesn't your car have afterglow? If so, the plugs stay on for a while even after starting, so you're gaining nothing by glowing less prior to start.

Except 4 seconds of glow time.

I know about it starting right up when engine temp is up but my car had been sitting since I shut it off at 6:45 am. At 1pm, it started right up in the 80 degree ambient temp.

Yes, some cars do this better than others. I found out by accident yesterday morning that mine apparently handles it suprisingly well, considering its age. With afterglow or at 80F, it probably would even have stayed running :) Doesn't mean I want to make that a normal part of my start routine though.

Yes, you save that, but that's all you save. With an afterglow system, by skipping the prestart glow, you are adding concussion stress to the cold->hot transition stress that the plugs experience. That certainly won't help increase their longevity, but I don't know if the decrease would even be measurable, much less matters in practice. So, if you need to save the 4 seconds, go for it. Me, I multitask and glow while I buckle, so I don't even notice the duration of the glow cycle in warm weather.

So, instead of going from 180*F to 1600*F in two seconds, they will go from 300*F to 1600*F in two seconds. :square:

You have to glow a 603 or it starts like crap, the 603 should be the same.

617's don't really seem to care once they are warmed up.

If my 606 has been warmed up and then sitting for a few minutes (so the indicator still reads about 80), I put the key in and immediately turn it to the start position. It always starts right up. But it should; this is exactly what the owner's manual says to do.