Timely topic for me. I had about 5 saw blades and several router bits that need a cleaning after building a number of storage boxes out of knotty pine. I had heard a lot about Simple Green Aircraft Cleaner which Simple Green Corp recommends for cleaning carbide. Simple Green sells the same stuff as "Simple Green Pro HD" (it's purple, go figure). So, today I picked up a half gallon at Home Depot for like $12.
I poured it straight onto the blades and bits, then scrubbed with a toothbrush and a brass brush on the stubborn parts. SGProHD is amazing stuff. As I was pouring it on the saw, it was lifting the tar off and turning brown. It took very little scrubbing and my blades are sparkling clean. Total time per blade was less than 10 minutes including prep and drying and about half of that was just letting it stand with the SGProHD. I think I used about $.10 worth per blade. By the way, this stuff also lifted sharpie writing on the blades.
So, to the original question - use something like SGProHD instead of Ethylene Glycol. It's biodegradable and non-toxic. EG is very bad because dogs really like it, can sniff it out, will drink it up and die. When I was a kid I knew some one who's dad was flushing his radiator and their dog got into the antifreeze - knocked over an open bottle and licked it up. Poor mutt died in agony.