You want 5/16" fuel injection hose. If you're running biodiesel or veggie oil you'll want viton lined or solid viton. The viton lined stuff is the SAE 30R9.

As for the air bubbles. It took me a long time to purge out all the air when I initially put in the VO. Nearly 100 miles before I got the last hiccough of air out. Try tightening all your hose clamps, and make sure all your fittings are tight. Do you have a looped return or no. A looped return will make it harder for the air to get out.

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