I just cooked up two 5 gallon buckets today and I had one of the best yields ever. Out of about 200 pounds of WW, I only collected about 15 pounds of lead stick-ons, and just a couple Zn. (I collect and save both for selling.) There weren't many Fe either, perhaps 10 pounds total, but they were removed with the steel clips. I'd say I pretty much aced an 75 to 80% total yield which is really weird. During my melt before in early summer I had tons and tons of steel and had maybe a 65% yield.
I have no explanation why there's so little consistency in my melts, especially considering I'm mostly using the same tire shops to collect my WWs from. Wield stuff. I just hope that Canada doesn't ban them like some US states have. I'm stocking up for my life time supply just in case though.