I believe that isspro reccommends if you run the guage without an isolator that it should be mounted outside the cab, but you can run it with straight diesel. That being said i ran mine into the cab using a tapped banjo bolt from the bottom of fuel filyer, needle valve, 2 ft of rubber fuel line(rated for diesel) then SS braided line into the cab. Even though i had the needle valve i still received a constant vibration thats why i installed the two ft of rubber fuel line.