What's the most effective way to wash your shop clothes that have lots of motor oil? I don't want to put it in the washer together with my regular dirty clothes to avoid spreading the oil onto them. Is there a good way to presoak them to remove the motor oil before washing?
Not necessarily a presoak, but if you use a product like original Gojo:
It will clean the grease/oil really well. You may want to run the stuff through a second time with regular washer detergent to ensure the washer is clean after use. The alternative way would be to take them to a laundromat and use their washer. Only needs to be run through once that way (though I'd hate to be the person who comes after you).
If you do go this way, ensure you get this type of hand cleaner, though. I doubt the orange types with pumice would work near as well (or maybe not at all). I'm not sure of how much to use of this stuff, but if I remember right, the reference to doing it this way was on the package, so it may have an amount to go with it and regular instructions.
Another product that works for oil removal is Simple Green:
In 2001, Crystal Simple Green was used to clean up an oil spill in the Baltic Sea.
I use spray bottles in my garage all the time to get grease and oil off of my hands (because I was too lazy to get my gloves, I guess?). A little rubbing and a rise in water gets almost all the nastiness off.
I've also used it as a spot spray in fabric. However, I wouldn't wash really oily fabric in my washing machine. That oil has to go somewhere and I don't want it in the washer. A bucket wash and a clothesline drying usually improves things nicely.
I has been tough to get the oil and grease outwith out a washer ring of oil left behind.
I used to run the washer on superheat at least two and some times even three cycles.
But fast orange for me is making that option no longer needed. It is not perfect but so far best I have seen. Still a bit of struggle with 90W gear oil.