Walk Behind Lawn Mowers

Just purchased your Hu700L to replace our old Lawnboy and was advised by the dealer not to tilt the machine on its side for cleaning, he stated oil may get into the air filter. We like to clean the machines, via pressure washer, after each use and we never had problems with either the Lawnboy or my Troybilt with cleaning while they are on their sides. Finding it hard to have to tilt front up to clean. Bad on the back for older people. Could not find anything in the manuals on this. Please advise your feelings on this matter.