Avoid B20 biodiesel and if you do have to use it do not switch back and forth between the B20 and B5 or non biodiesel fuel as that will cause even more problems. B20 also causes the most problems during the winter months and the newer trucks have fuel heaters to minimize gelling problems with this fuel.
Big ag corporations are gaming the system and even the US Congress bends over backwards to accommodate Archer Daniels Midland and the equally infamous Koch brothers. As cars and trucks become increasingly fuel efficient the law which pushes a fixed quantity of biofuel production results in larger percentages of these being added. Same problem is happening with ethanol and gasoline and this is causing even more damage to car/truck and especially boat engines.
This is from the GM owners manual:
Biodiesel fuel quality degrades with time and exposure to high temperature much more quickly than conventional diesel fuel. Biodiesel gels sooner than conventional diesel fuel at cold temperature, and biodiesel fuel requires proper blending for winter time operation. Fuels improperly blended for cold temperature operation may result in restricted fuel filters and degraded vehicle performance.
Your vehicle is equipped with a fuel heating system to provide a level of protection against filter plugging from gelling (waxing) of conventional diesel fuel and biodiesel blends. However, the system will not prevent all cases of plugged filters if the operating temperature is far below the temperature at which gelling or waxing of the fuel occurs (cloud point). Use of biodiesel blends greater than B5 (5% blend) should be avoided in cold temperatures.
Vehicles operated for extended periods of time on conventional diesel fuel and then switched to biodiesel blends may experience premature fuel filter clogging and require more frequent fuel filter service.
With long term use of conventional diesel fuel, gum and varnish may be deposited within the tank and fuel system. These deposits, while not problematic with the use of conventional diesel fuel, may become loosened with a sudden switch to biodiesel blends and cause fuel filter plugging.
This vehicle is equipped with a fuel filter restriction monitoring system that will alert you if the fuel filter requires service, but it will not prevent damage caused by poor quality biodiesel.
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Note that damage caused by biodiesel fuel is not covered by the GM warranty.
It may pay to get a larger main tank or add an auxiliary fuel tank to be able to avoid B20 biodiesel altogether.