[101Volts]

Yesterday:

Topped off the tires, filled up the tank. Got 20.2 MPG over 410.5 miles. Put 4 oz of Opti-Lube XL in the tank before the refill (same as the previous tank,) and added 24 Oz of Marvel Mystery Oil to the crankcase since I'm close to changing the oil. Also bought a tarp and silicone for both a grill block and roof rack delete.

Over the 83.x miles I drove on the same day after the refill, the mileage had increased to 21.5. The engine had already been warmed to 195F, but I'm not surprised about an increase since I put the MMO in the crankcase; the oil viscosity's thinner now.

I've seen my mileage differ in the Suburban, depending on which Oil I used. Oil Viscosity matters, and it's a bit of a low hanging fruit mod. The Suburban got these rough MPG figures with these oils:

Amsoil Heavy Duty 5w40: 18 MPG
Mobil 1 Turbo 5w40: 20 MPG
Shell T6 5w40: 20 MPG
Shell T6 0w40: 21 MPG

Shell T6 0w40 is one of the thinnest Diesel 0w40s that I can think of.

EDIT: I have now removed the Roof Rack, and put Silicone over the bolts.