Think you have
Muffler cement, which may be same/similar to fire cement.
Thinking the Hi temp silicone may not stand up to the VERY Hi temps of the
Diesel heaters exhausts. Best to check with manufacturer.
I used the recommended
Muffler cement (which I did'nt want to use as it dries hard as stated above) but stands up to the hi VERY exhaust temps, so far so good.
Muffler cement...1500 F/800C
Thinking some
diesel exhaust temps can be 500-700F but not sure I remember correctly. I triple wrapped my exhaust with expensive
race car manifold
insulation and is still hot.