quote:Originally posted by BAdolph:
If oil breaks down from shearing, how does recycling the oil fit the picture?
For the most part, what gets sheared is part of the additive package, namely the VI improver. As the VI improver gets sheared, the oil moves closer and closer back to the original base oil viscosity.
All things being equal, an oil with no VI improvers would be the most shear stable.
A lot of recycled oil is blended into heavy fuel oil. There may be other low-tech uses for it.
Some used crankcase oil is rerefined, and there's not a lot of info around about it. Both the rerefiners and the government agencies promoting recycling claim that rerecyled oil is as good as new.
In any case, the degree of shearing of the VIIs won't make any difference.
I remember an add from quite a few years ago which was selling a furnace that burned used motor oil. I don't know if this product's still around, but I seem to recall that it was targeted towards repair garages which accumulated a lot of used oil, & they could recycle it back into heating the shop. I'd imagine that oil recyclers couldn't just drop off used oil at your doorstep.
I also used to buy recycled motor oil at WalMart, but that was about 4 yrs ago. I think it was a 10W-30, but I haven't seen it there since that time.