You know I was looking at that dipstick holder a few days ago as I seen what happens when it snaps and when they remove them wtf, you can get metal ones through, so it won’t be just petrol it’s just any that have that dipstick design.Most of the pickup blockages either come from bits of plastic from broken dipstick guides, or from people using too much sealant/RTV when doing rocker and sump gaskets. If you've owned the car for years and have done regular oil changes and avoided both of the above, then i wouldn't say you need to clean the pick-up at all.