Castrol superclean is a good all around cleaner degreaser ive used it on engine parts and its even gotten melted strawberry ice cream out of my grey cargo van seats...
I have cleaned many really really really greasy stuff. The harshest stuff is Brake cleaner and Easy off oven cleaner. I use a combination of stuff all over the car. I clean a lot of stuff on the car. Use brake cleaner on really greasy parts of the engine. Some suspension parts and rear ends I use easy off oven cleaner. WARNING. Easy off WILL take off paint. I use it if I am going to repaint the part. Have not had any problems with seals.....I would not use it on the engine......with both of these products make sure you have good ventilation....ask me how I know. "cold winter+closed garage+3 cans of brake cleaner=almost dead Buick enthusiast."
Easy-Off has two formulations, yellow and blue. They Yellow is the most harsh, I've used it to strip paint. Blue is more agressive than Scrubbing Bubbles bathroom cleaner. I use it on my old 1950 bathtub and it doesn't smell as bad either !!!
This stuff is the sh!t. I use it with a hard tooth brush or a tooth brush style wire brush and hose the stuff off. It will emulsify. I especially use it to clean parts.