I've used Royal Purple, other suggestions, and general auto parts "Engine Degreasers", i guess they help but weren't magical.
I know heat helps and @GeneralDisorder has posted about using a hot water heater and pressure washer. 

Maybe I should try my pressure washer and see what happens and plumb a hot water fitting into my basement for hot water since I'm about to do plumbing work anyway. 

The POR15 degreaser works well. 

https://www.por15.com/POR-15-Cleaner-Degreaser

One thing about plumbing the hot water heater to your pressure washer.... most if not all consumer grade pressure washer pumps are not rated for hot water and it will destroy them. Not immediately but it doesn't take terribly long. You can get pumps that are rated for it after you kill the first one but they aren't cheap. 

GD

On 3/23/2019 at 1:54 PM, GeneralDisorder said:

most if not all consumer grade pressure washer pumps are not rated for hot water and it will destroy them.

Ah thanks I totally would have done that!

you can also use a laundry degreaser like shout to clean up the engine bay.  I spray it on, let it sit and then rinse it off and it is not as toxic or crappy smelling later as the engine dries.

5 minutes ago, 3Pin said:

you can also use a laundry degreaser like shout to clean up the engine bay.  I spray it on, let it sit and then rinse it off and it is not as toxic or crappy smelling later as the engine dries.

I doubt that will work, you may mean the same thing but I'm not just talking about cleaning an engine bay to make it look nice but rather tons of oil caked on everywhere so i can find the leaks.  i've tried a lot of cleaners/degreasers and none of them really work that well for getting off loads of leaking oil from the underneath.  

Harbor Freight yellow degreaser has worked really well for me in the past. 

14 minutes ago, 86BRATMAN said:

Harbor Freight yellow degreaser has worked really well for me in the past. 

Thanks i'll pick some of that up and check out the POR 15 too if needed.

Nothing like a  engine steam cleaner for that, but multiple degreaser will work.  I though you just wanted to clean her up a little.

 

It really is a job for a Hotsy.