So I bought some BG 109 Compression Restore to run in my '89 BMW 325is with 241K miles on it. I was ready to change my oil when I saw that on the can it reads in bold, capitalized letters: DO NOT USE IN HEAVILY SLUDGED ENGINES. D'oh. Well, I'm pretty sure my engine has sludge (the oil instantly turns black only a day or so after an oil change), but how do I know if it's "heavily sludged?" What would be the danger of running the additive as is?