Mineral Spirits is a great degreaser. It's what I use. Sometimes if I run out of mineral spirits, I use lighter fluid instead.

Mean Green. Rinse. Dry. Gets rid of WD-40, tobacco, and anything else people have used over the years.

I'm going through my whole machine since it had been spray-lubed and everything was grimy. Disassembling all the steppers and solenoids, degreasing, reassembling. I'm using alcohol on stuff that's not getting dunked like solenoids and contacts. Using Purple Power for all the stepper parts, plungers, etc. that are getting dunked. It's working great. Scrubbing with a cut-off paintbrush and rinsing with water. They come out like new. I used up the last of my Simple Green Automotive before buying the gallon of Purple Power. It was similar but I think I liked the Simple Green better than the Purple Power. Maybe not enough to justify the price. It doesn't affect the sticker labels on the units but it does take off some of the quality control stamps on the nylon wheels. Not too worried about that as mine's not a collector's piece, I'd rather have it all nice and clean. Also cleaning the board as I remove parts since everything has a film coating... A damp paper towel with barely a drop of Dawn works great.

+ 1
like my ex wife, it is cheap and easy to use.

Brian

Wait, are you talking about cleaning parts while they're still in the machine? if so, I'd bee leery about
Spraying anything into / onto a machine.

As far as using alcohol, there's lots of grades of it that are anywhere from. Short of using denatured alcohol I've found that 91% isopropal (you can get this at Target) is good for cleaning off grease and oils from metal and unpainted plastic parts.

Doing full tear downs, Naptha works great, Pros: easy to dab a little on a cloth or paper towel, evaporates at a good rate (not as fast as alcohol, but fast enough to move quickly). Can be purchased at box stores. Cons:leaves a residue, but that is easily wiped away, should wear gloves (nitrile), and ventilate if using more than a few drops at a time. Dirt, grease, other. If that doesn't work, I'll try something else, but works great on metal parts.

For grimy or greasy parts, I predominantly use 91% isopropyl alcohol or Mean Green.

No smell - actually helps rid the machine of tobacco smell.

Take it out of the machine? I always go through every part of an EM. I pull the bottom board, take apart and clean every stepper. In the back box, I just disassemble a stepper, clean it, put it back together and go to the next one - I don't remove it from the game.

I use it for almost all surfaces - metal, wood, wiring, I clean most era's of playfield plastics with it. It removes the tar and nicotine and most of the yellowing (not all, some is age related).

For rinse, I just use a spray bottle of water. I don't drench it, but enough to wipe off the cleaner. I don't worry about getting 100% of the Mean Green. A little bit left is nothing compared to the decades of grease and grime I'm getting off. You can tell be feel if it's still sticky because of too much left on a part.

I use it to clean the wood too. It cuts through years of tobacco yellow.

That said, I've been doing this since the early 1980's. 90% (or more) of the machines have been sprayed with some sort of lube. I have learned that it is better to take your time, do it right, and have a trouble free game. Nothing worse than fixing a problem, playing a few games, another problem occurs, fix the problem, repeat.

Now, if I get a mint EM (rare), I use much more caution. There are not many of those around. So, this might sound extreme, but most EM's are pretty dirty and beat when they appear.

Get a still and use "Heads" for degunking.
Pros: 8-9 Ltrs of 40% ethanol for consumption.
Cons: 8-9 Ltrs of 40% ethanol for consumption.
Cheers

Seems the topic is more broad than I discussed in my previous post. I do use several other cleaners, Mean Green for sure on many surfaces. On metal, nothing works better for grease,than Naptha IMO, followed by polishing with either Blue Magic, or Novus 3.

For stepper units that are very junked up, I like to you some "Break Free" gun cleaner made by Winchester (you can get it from Walmart). Helps when you don't want to dissemble the unit but need it to be clean and lubed. Use sparingly though. Not sure where I got that recommendation, but the stuff works wonders.

Depends on what it's made of, and the type of dirt. For heavy grease, as in the title of your posting, charcoal lighter fluid or paint thinner works good on metal parts. WD-40 is actually very good for removing light greasy gunk on stepper discs and other parts, but wipe away any excess with a clean cloth. I use Purple Power, Mean Green, Super Clean or similar products on plastic parts. An old toothbrush is invaluable for scrubbing away crud on small parts.