Does the stop leak products really work at all?

It might help with the valve cover but the rear main seal has the moving crankshaft that won't allow the product to help there.

I wouldn't use it myself

DON't USE IT! you are FAR better of using a total MOTOR FLUSH chemical to loosen up the sludge fromed around the selas and gaskets, then CHANGE wt ofresh engine oil esp SYNTHETIC> the SYNTHETIC has lots of detergent that can WASH the junk out of the REAR MAIN SELAS. These SEALS are like spring bound, and SLDUGE will form in the SPRING part and clog it up. Next oil will leak from the edges. The VALVEE cover will NOT recover with any additives. They must be TIGHTENED DOWN or REPLACED! GOOD LUCK to you!

I had a front seal in my transmission go bad and I tried some stop leak in that, it held for maybe 2 months and it came back. So I would say try it to hold it over if you have to wait for your next paycheck but try to get new gaskets in as soon as you can

i will cause more damage than it will fix

no