Is 87 octane dirty gas?

No it is not dirty gas. Most newer cars will run fine on it. Only the older V8 motors don't run as good. With the price of fuel some of stations here in the south are dumping water in the tanks. I don't know what is happening to your car but it could be a clogged fuel filter or injectors.

Octane when added or subtracted from fuel either increases or decreases the compression it ignities best at thats all the octane rating is for for example if you drive a vehicle with a high compression engine (some foriegn cars and sports cars) these engines would require a higher octane of fuel like 89 90 all the way up to 93 the fuel is just as clean (as whatever manufacturer makes it) whether you use 87 or 93 another example of this is if you have ever been to the dragstrip in your area they sell 110 octane at the pump because most race engines are stroked for higher compression low octane fuels sometimes wont even burn at all in these cars. If your car is running poorly on 87 then more than likely you just need to change your gas station. Actually running higher octane fuel in a low compression engine would make it have less fuel economy and cause more carbon build up on piston heads which would increase compression but decrease volume inside the piston chamber and ultimatley shorten the life of piston rings and catylitic convertors.