I've never even heard of Mouse Milk, but I'd hate to be the poor sap who has to hook the milkers to the squirmy little critters.

When I've had to extract plugs that were rusted into place after years of sitting on an unused vehicle, I've always blown the crud away from the ports with compressed air, then soaked them down with Knock'r Loose and then fit a deep socket over the plug such that it sat on top of the jacket, and rapped on the socket with a lightweight hammer. Doing that a few times per day for two days has always worked for me. The same technique, sans socket, works well for freeing stuck valves on an engine that's sat unused for a long time -- just don't hit them so hard that you deform the stems or you'll hate the result later.

A good piece of pipe or a breaker bar has never failed to loosen even the most stubborn bolts, at least for me. Got an impact wrench?

Hey, finally someone else on here has used Knock'er Loose
That can end badly with spark plugs. If you manage to snap the threads off in the head or strip them then it will be time to pull it to drill and tap it.

I thought some of those other products were the best until I tried the Mouse Milk. You probably have to order it.

true story - mouse milk has a very short shelf life. acetone/ATF mix is a cheap do it yourself mix.

more BS - it requires very small fingers to milk the little boogers.

back to true story - i would try all other methods before using an impact or extremely long breaker bar on a spark plug. the odds of making things worse are high.

Very high.

I was about 12 or 13 years old the first time I had to remove a head to Heli-Coil a spark plug port (on a motorcycle), and about 15 the last time (on a V-8). I learned not to use muscle when finesse is called for.

breaker bar = very high FUBAR factor.

You just have to be smarter than what your working with.

i wish i could find CRC Knock'er loose. no auto store around here sells it. the only CRC product they sell for removing rusted bolts is something like Freeze Off. don't know if i would use freeze off on a plug put go for any CRC product..knock'er loose

a lot of people say not to break the porcelain part of the plug, but if this happens, is the plug FUBAR? i could see why if you were installing them they would be a problem but removing them?