oil drips and spots

[Lee]

Look at any place where vehicles go and you will see oil spots on the ground. They are small and of various shades of black, grey, brown, etc.

I use an old tooth brush to create this effect. Dilute some acryic water base paint. Dip the bristles in the paint, turn the brush with the bristles pointing up and flick the bristles with your thumb. The dryer the brush, the smaller the drops. Try this outside first until you get the hang of it because it splatters, which is what you want. with a little pratice, you can create all kinds of effects on roadways, driveways, etc. Use different colors to get a realistic effect.

[perez]

very good idea Lee! it really looks neat especially wwhen u make believe that u had a garage in Ho scale and where the trucks are parked in a truckstop -Perez

[cfesmire]

Just to add to what Lee has said, if you would like to give the look of a fresh oil drip/spill, after the color goes down, add something glossy to give it that wet look. I simply use a clear gloss lacquer that you would use to clear coat a model and apply with a toothpick.
Also take an old tire that has a distinct tread pattern and roll it into and over the drip/spill while it is still wet like someone ran through your puddle of oil. If you're feeling real whimsical, even a footprint or two is in order.
It's easy to be messy.