After going out in the boat today, I decided to drain the oil tank on my 115 Johnson outboard. At the bottom of the tank was about a 1/4 inch of gelled oil. The oil in the tank was a mix of Quciksilver Premium Plus and Castrol Super Outboard. Both oils are TCW3 certified, which means they should have been ok to mix. Anyway, what can I use to clean the gel out of the bottom on the oil tank, so that when I put in two gallons of fresh oil, the cleaner or solvent will not contaminate the new oil. Any suggestions??