It's actually a common practice now among the larger trucking giants to do just that. They usually mix it in at about 10% but I have seen it done much higher. Say maybe twice that? I mean when you think about it an oil change on a 60 series Detroit or a Cat. or Cummins your talking about between 10 and 12 gallons of used oil. Then just stick it in the 150 gallon tank and top it off.

It DOES need to be filtered though, I would suggest 5 micron which is what MOST fuel filters are. I have sock filters that I use to filter my biodiesel with , they are washable and I LIKE that. I have a 25 micron and a 5 micron. The 25 is about what an oil filter would be, and you wouldn't believe how much crud will pass through the 25 that gets stopped by the 5 micron! There is a lot of crap in that "in-between" zone! To see an equally amazing comparison drop down to a 1.5 micron, this is finer than a coffee filter!

I got mine from Grainger, I figured I would tell to save time. ( someone is bound to ask!)

I didn't look to see where that fella lives that they use #6 fuel oil, but THAT would suck! We use #2 up here, yes same as you buy at the truck stop just a different color dye.

Do they still put oil on the roads there? I wish they would quit using chloride in Mi for dust control, sure is hard on the car, and my wallet from every other day washes! I personally think if they quit spraying that stuff on the road there would be fewer critters getting hit. ( road kill) You wouldn't believe how many squirrels I see licking the road because of the salt! Tom