What solvent to use for parts washing

"Safe" and "effective" are largely mutually exclusive. If it's "safe" it will take forever and a day to do anything, and if it's "effective" it will require reasonably PPE like splash goggles and gloves. I generally use the "purple" degreaser for my parts washing needs. Simple Green is also reasonably good used in a heated ultrasonic cleaner for smaller parts. On that front, the good Harbor Freight #95563 ultrasonic cleaner is on sale for $59.99 in the latest mail flyer, which also has a 15% coupon on the back. $51 is definitely a steal on that unit.

Both are bad for aluminum, but do the job. "normal" solvent is Stoddard Solvent, AKA "paint thinner". It's getting harder to find in California, as it worked too good to be allowed.

I went to our local chain Menards, and they had a 5 gallon bucket of mineral spirits based parts washer fluid for $36. I bought it.

Diesel fuel or kerosene.

Sooooo.... WD-40? It's my favorite cleaner/de-greaser.

Dave

If it's fire-safe that concerns you, it is possible to use water plus a tub or three of waterless hand cleaner as a cleaning solution.

The milky liquid that results is a slow acting grease solvent, but has all the soapy-water cleaning power for other kinds of gunk that you might need. It also clears up greasy rags pretty well.