The "search" function didn't work for me just now, so I can't find the old thread I posted to a long time ago, but I can guarantee you that the grease and oil you have from servicing your vehicles can spontaneously combust. One hot summer Saturday about 22 to 24 years ago, I changed oil and greased our vehicles in the garage and was using an old worn out white t-shirt for a grease rag. At that time, we had a special rack with a lid that held our plastic garbage bags in the garage. When I finished, I threw that old t-shirt in the garbage bag, went in, took a shower, and my wife and I went out to eat. When we returned, as soon as we entered the garage, I smelled something burning. I ran into the house and went through the house fast looking for the fire, then realized the odor was strongest in the garage. I found that, while I was showering, my wife had thrown a small bag of garbage from the kitchen into that big garbage bag on top of that t-shirt. I burned my fingers a bit getting everything out of that bag. No flames yet, but that t-shirt was severely charred and too hot to touch. I do believe if we'd been another hour coming home, I'd have burned the house down. Needless to say, since that day, I always do one of two things: either spread oily rags out where they can get plenty of air all around or I put them in a metal container with a tight lid.
