on amsoil XL7500 in a ford focus, when should I do my analysis? this was the first dose of amsoil, I ran Valvoline conventional from the quick change (every 3K miles) for the first 18K miles
Now might be a good time or some would say dump the first batch of XL7500 and sample at 5000 on the second one. It will flush most of the Valvoline additives and residue out giving a clear picture of the second fill of Amsoil.
