I have just three oil colors in my arsenal: Ivory Black, Burnt Umber, and Burnt Sienna, they are Georgian, and I picked them up at Walmart for like 4 bucks a tube. Michaels have excellent oils, but unless I have the weekly 40% coupon their oils are too expensive for me.

But there is a thinner I get from there that I have been using for the last year, and have had no problems with. It's called Better Way Artist Oil Brush Cleaner & Thinner. It's colorless and odourless. Great stuff, and it doesn't seem to eat through Future. I have three jars of pre made oil washes ready to go: Burnt Umber/Black for vehicles/figures/ground work, Black for darker rubble/cobblestone roads, and Burnt Umber/Burnt Sienna for skin tone washes.