If the environmental impact assessment (you should already have conducted this) shows the impact of dumping your 1 ml - 1,000 l is less than the impact of your driving 45 miles, go for it!
> Would you say that it is therefore OK for me to dump it in the ditch?
I'd say no - because it's decreasing the intrinsic value of a shared resource (whether or not it can be measured). Downloading a movie, on the other hand - doesn't decrease the intrinsic value of the media being copied.
The amount of oil is small enough that it would have absolutely no measurable effect whatsoever on Puget Sound.
Would you say that it is therefore OK for me to dump it in the ditch?