My '82 300TD has been eating glow plugs for the last few years, and it's been really accelerating recently. Now it's at the point where every few months 1 or 2 GPs will be dead. For example, maybe 5 months ago I changed GP 1 and 2. Then last week the car just would not start at all, so I checked and GP 1 2 and 3 were dead.

I bought a reamer, thinking that it was just in dire need of reaming. Well holes 1, 2, and 3 were all clean. The only thing the reamer picked up was a tiny amount of sludge. The dead GPs were covered with black sludge. It's like a thick black oil, which I'm assuming is blowby.

My question is, is that black oil really blowby? Also, what can cause early GP death, aside from carbon build up? Can blowby oil be killing the GPs?

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'82 300TD
'77 6.9
'75 280S
'74 280
'87 Porsche 944 turbo