Penray’s crankcase and differential cleaner

[Hammerhead]

I'm not sure how much a quantity that small could really do. Reading the instructions it says to add to diff, roll back and forth 20-30 feet (it doesn't say how many times, only NOT to drive with this installed) then drain. I don't see there being that much mixing agitation in 20-30 feet?
I won't leave my rears go into the winter time to do oil changes, because they just doesn't get warm enough to get a good drain. I do them myself, and I do it when I come home loaded and drop the oil as quickly as I can to have them hot to get as much old oil out as possible.
(Playing Devils advocate) On the other hand, Penray makes good cooling products, and there test strips and DCA are all I ever use...
I'd be interested in hearing if you believe you had better change results using this product.