I call that stuff sprocket fudge ...
Well, my sprocket fudge was dark, double chocolate for sure. 16VGTI saw it after I scraped the big chunks out and gave 2 applications of engine de-greaser foam and 2 hosings.
I think I am going to switch to wiping the chain off with wd40 and using a can of chain lube as Drewpy suggests, and then see if I still make fudge. My oil level really doesn't drop noticeably between changes but I will keep a close watch while I read up on the how/when/why of seal replacement.
What brand/model and what was its tensile strength?
Oh and...
Both chains are 530. I inherited the chain that broke from the PO 12,000 kms ago. It was one year old then but I don't know how much distance he put on it. The only markings are
"TYC 530HP".
The replacement is a
"D.I.D. 50" roller chain made by Daido Kogyo in Japan.
It's interesting that the instructions say to clean and lubricate with sae80w-90 every 300 miles. I was slathering it with 10w-40 every 50 miles or so - no wonder I made lots of double chocolate fudge.
Thanks for the tip on how to judge the wear

I will try and do that every so often - maybe every 300 miles when I clean and lube.
I ran into a bike mechanic today over coffee and he advised me to check the alignment of the rear wheel (he said not to trust the hash marks absolutely). Apparently if it's out even a fraction, it will strain one side of the chain more than the other and will eventually show up as unbalanced sprocket teeth wear.
So, tomorrow I will try his plumb line technique ... - if I can remember it.
