You can easily clean out a gunked up engine by merely doing regular _hot_ oil & filter changes ,
every old nail I buy seems to come full of sludge , I just do 500 mile oil changes untill it's shiny clean inside .
I'd be leerly of driving with anything other than a cupful of ATF in the oil though .
If you use synthetic oil , all the crud will be loose & swirling about in 50 miles or so .
