Our poor little 197 hasn't caused any trouble, mostly I think because it is usually used for long runs. This last one was 3500 miles. I do make sure that lots of water gets in, and sometimes will scoop the dishwater into the toilet. I use el cheapo liquid laundry soap quite liberally. After dumping, I usually pour in a couple of gallons of water and maybe a cupful of two of soap. Also, I think there is a baffle sitting right under the bomb door, helps mix things up.
2012 Jay Feather 197 w/pull-out
1997 GMC Sub 1500 4x4;
or 2015 Ford F150 4x4 SuperCrew EB