When I worked in Saudi we built 20+ Motocross tracks in the desert, from being bored mostly.
We went around to all the truck oil change places, they GAVE US used oil in 55 gallon drums. It took dozens of barrels to make one track. We used a front end loaders and mixed up the "ashtray sand" with the oil to make 100% super fine MX track material!
It was good stuff. They made golf courses out of it too! You had to use "Winter Rules" when you played and place the ball on fake Astroturf, but I digress...
I didn't see any birds dropping out of the sky or dead seals. Just lots of smiles from fans. We even had their military out watching us race and later drew a crow while practicing! It wasn't oily, but WAS good incentive NOT to fall down because you would get yucked up - besides risking being run over!
MY WIFE RODE TOO. We dressed her up, most of her was covered with MX gear, (YES she HAD to WEAR a chest protector tho). She looked like a guy and some of the locals almost fainted when she took off her helmet and the blonde hair fell out! (NOTE: Ladies ARE STRICTLY FORBIDDEN to drive there - the locals even gave our U.S. Military static about female drivers - except our Military had machine guns, the dispute ended there).
The point is, a few gallons of oil is not going to 'ruin the environment'. Besides, can you see lugging an oil container in a Porsche? Now, if you live in the city, that MAY BE a different story…but in an ashtray? No big deal.
So, I guess you could say I left a lasting 'impression'!