Welcome to the forum, glad you joined us. 
I remember those Rugg riding mowers from the mid to late 60's.
Not sure what exact years they were produced though. Would like to see a photo of yours if you can post one.
Usually the grey color comes from metal dust worn from the engine, and accumulated in the pan, when the oil isn't changed for years.
You said that you've cleaned all that, which makes me at a loss. Sorry, that's all I can think of, but maybe someone who is more familiar with those engines will know how to help.
I remember those Rugg riding mowers from the mid to late 60's. Not sure what exact years they were produced though. Would like to see a photo of yours if you can post one.
Usually the grey color comes from metal dust worn from the engine, and accumulated in the pan, when the oil isn't changed for years.
You said that you've cleaned all that, which makes me at a loss. Sorry, that's all I can think of, but maybe someone who is more familiar with those engines will know how to help.
