The "problem" with many over-the-counter de-greasers is that they are NOT safe for use on aluminum. How would one know? READ THE DIRECTIONS ON THE LABEL! (OR as Accumulator abbreviates "RTFL" meaning "Read The F`ing Label".) If it says, "Do not let it dwell on aluminum" or "Rinse thoroughly from aluminum parts", be wary of using it. OTC Simple Green falls into that category, as does Super Clean (the Purple Stuff).
Zep`s Citrus De-Greaser probably would make a good OTC de-greaser.
Even LA Totally Awesome (Yes, the All-Purpose Cleaner at the Dollar Stores) might make a worthwhile OTC de-greaser.
Personally, I still like Optimum Polymer Technologies` Power Clean as my go-to degreaser. But I know you are looking for an OTC de-greaser. The Gunk De-greaser in a can is more of a parts cleaner from what people think of it as than a "de-greaser" .
Other option is to go to an auto parts store and ask them what they recommend. Just remember to read the label before you make that purchase.
If you have a Cenex Farm Co-operative near you, ask for Schaeffer Mfg. Citrol 266 HD De-greaser. It is what construction and excavating companies use on their heavy machinery. Should work for you as well.
As a side note, if anyone uses Meg`s Detailer Line D108 Super Degreaser Concentrate, let us Autopians know what your thoughts and opinions are from experience with this degreaser. It is a "less-expensive" alternative to OPT Power Clean.
I have used Meguiar`s D108 Super Degreaser for perhaps 15 years or more, and it is always the best for my needs..
I usually just spray it, let it set a bit and pressure wash it all off.. If the grease is really thick or something, I might spray it, use a plastic semi stiff bristle brush with a long handle, on it, to help the product get going faster..
Have cleaned a few hundred engines, all the German marques, engine compartments, underhoods, that space between the front grill and the radiator, underneath; even entire really dirty vehicles full of little trees growing out of all the spaces of a vehicle, with this product before I washed it
.
Never had an issue, always rinses quickly, is very low foaming, which is really nice, and never leaves residue..
It is not oily like some degreasers, very easy to work with..
A great product to use after you open up the gas filler door and are horrified by all the crapola behind it, and in the compartment...

This is always a place where that plastic bristle brush works great with this product, then let it set, then pressure wash it all clean..
I will spray the places that need it as I go around the vehicle, and by the time I get back to where I started, pressure washer rinse and go back all the way around it ..
Would never consider using it on coated vehicles, or any vehicle that I am not going to be paint correcting and applying an LSP, etc.. It just might be too strong for those things, and I don`t want to find out if it is..

Dan F