Hey Guys!
I've been told I need an Engine Flush and the dealer wants to charge me $300.00 for it. To be honest I'd rather learn and do it myself. Only thing is I can't find a straight answer online! Hopping you guys can help me out

Is it just the oil system or coolant as well? I have a 2004 Honda Hornet and anything you can help me with would be very much appreciated!