The grease I collect settles to three layers: the first two-thirds is pure canola; about a quarter below that is animal fat, and at the very bottom is a small layer of water (from the moisture and frost on the chicken tenders and fries when they're cooked). It's a pretty simple process to pour the pure canola into a bucket, and then stop when you hit the animal fat. I've never used the animal fat before, though theoretically it's supposed to work in the car. Well, I was desperate for grease this week, and decided to filter some animal fat dregs and stick it into the grease tank. I was planning on driving it, but the wife got in the car before me to take the kids to a play session (which involved driving on the highway). Furtunately, the engine didn't blow up on them when they were driving 60 m.p.h. In fact, everything worked fine.