What makes you think filling up with 98 octane cleans the engine? Higher octane fuels don't contain a higher volume of cleaning agents than 87 octane. If your owner's manual states 87 octane then the only thing higher octane will do it deplete your wallet faster. In order to truly CLEAN your fuel system you need to use a dedicated product - like SEAFOAM. I've used it for years in many different applications with excellent results.
'I use my cigar smoke as idiot repellent'
Yeah, that’s a statistic sample size of 1, category “anecdotal evidence”, but there it is.
"You just got killed by a Daewoo Lanos motherfu#&er!!" -Red, from Pineapple Express.