Your stabilizer and Gas treatment fixed the GMC knock in my engine block the first time I used it!!! I own a 2002 GMC Yukon XL 2500 series and with the really short pistons it is a characteristic of this engine to knock at cold start up and a couple minutes after till thing warm up.

...BUT not with Lucas Oil on the job. IT IS ALL BUT ELIMINATED MAYBE FOR A TENTH OF A SECOND till oil pressure build up....

thanks LUCAS oil!!!!