I've been doing it for years and it seems to be fine. My intakes don't look gummed up. My boy is old enough to hold up the funnel and dump the antifreeze into it which is connected to a hose connected to the flush port. It takes about 30 to 40 seconds for a half gallon and I fog all the engine through the intakes during that time. Super easy. I also pinch off the flow from the pump grate to prevent antifreeze from just going back out that pump grate.