I have my doubts as to their effectiveness as well, but for the cost it's worth trying. However I feel that the weak link in the heat transfer chain is the steel oil filter. Removal of the paint will help, but the thermal conductivity of steel is far less than that of aluminium. I've seen this when I switched from using an aluminium fuel rail to a steel fuel rail. Due to the close proximity to the turbocharger I was picking up allot of heat as the excess fuel was recirced. I made a few other changes as well, but I feel that had a large effect. Now if we could find aluminium oil filters to use with this Cool Collar we might see a small result.

Todd (going to wait for Paul's report before I buy)

 I'm gonna go with Al, and say that it won't do much (unless, it comes
off like Rusty said 8*(    But some things you might try to make it better:

1)Strip the paint off the oil filter.  For its thickness, that paint
will do an amazing job of insulating between the two material.