Try selling it in a different market. Like one where grease is more readily available. Seattle is tight and there are a lot of hippy freaky type people that want an ecofriendly car but are realizing there is not any grease. Take a loss is probably. If your burned 800 gallons of grease and save $3 per gallon on the cost of fuel you are up $2400. And you should take that into consideration as well as the learning process. I am assuming you got a grease truck. I have put 50k miles on my Mercedes and saved about $4 per gallon on fuel. I figure I am up at least $6000 is saved money on just that car.