Originally Posted By: Shannow
Polarity and MW ?
On topic, we use a lot or re-refined oil for auxiliary fueling the boilers at work (250,000L for a cold start), 10-14Cst blend of used re-refined oil and diesel.
We had huge blockage issues a couple years ago. 5um filter as it goes onto the truck, and 25um filters blocked at the boiler.
Turned out to be glycol in the waste streams surviving the re-refiner, and then collecting (agglomerating soot particles, and forming quite strong stable particles).
They upper the upper temperature of the re-refiner, and problem went away.
Yes, the polarities of DOT 3 and motor oil are too dissimilar to allow miscibility. The brake fluid is more polar. Perhaps at high enough temperature they would be miscible but not at room temp. and 125F.
I ended up adding the brake fluid because for weeks I had been experimenting with seeing if motor oil would dissolve a sliver of varnish that was composed solely of oxidized vegetable oil. The answer was “sort of, but mostly no”. I used Amsoil 10W-30, Maxima Formula K2 2-stroke oil (mostly esters), and Hy-per Lube polymer esters, separately. They did soften the varnish and give it flexibility that it lacked when dry. It also swelled. With gentle shaking, they did cause it to partially split apart. A very small piece or two did break off. Today I added brake fluid to the Amsoil that was already there. The varnish got even more flexible and swollen. Quite a few chunks broke off. The varnish became the consistency of mucous. DOT 3 is definitely more capable of dissolving vegetable oil varnish than the three other fluids I tested.
That’s an interesting story about the blockage from ethylene glycol.