I did Seafoam in a ten year old Police Interceptor Crown Vic with 80k miles. Put on a hell of a smoke show. Ripped it through town, went home and did a spark plug, air filter, oil and oil filter change. Ran so smoothe after that. Been 3 years since, still running strong more than 30k miles later.
1999 Grand Cherokee Limited, 4.7L V8, QT II, AWD, Brush Guard, 31x10.5x15"s. BB otw.