Thanks for the thoughts. Anyone else?
I talked to the owner briefly and have already committed to picking up their used oil tomorrow. Should be about 15 gal. I'll look into it and if it's gonna work I'll keep collecting it but if it's hydrogenated or solidified I'll dump it back in their tank and tell them later it won't work. Don't wanna seem ungrateful.
I'll post findings later.

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1983 M-B 240D-Gone too.
1976 M-B 300D-Departed.

"Good" is the worst enemy of "Great".