Important Note about the Fuel Gauge Operation:
The distance to empty (DTE) on GM trucks can’t be reprogrammed, so it will show about half the mileage that is really left. This occurs with all aftermarket high-capacity fuel tanks.
The fuel gauge will operate properly. When you fill up your tank, the fuel gauge will remain on full until about 4-5 gallons have been used and then the gauge will start to move normally. GM trucks monitor for an inoperative fuel gauge, so in some situations, until it starts to move, the truck’s computer will drop the gauge to empty to get the driver’s attention even though your tank is full. The gauge will return to its normal position after restarting the engine. Once the fuel level drops 4-5 gallons from full, the fuel gauge will return to its normal operation.
The bottom of the S&B tank has more surface area than the OE, so there will be a greater fuel reserve when the low fuel indicator comes on.