Originally Posted by Phinias
make sure that you research fuel in your travel area in advance. Fuel containing more than five percent biodiesel could void your warranty. I asked customer service for advice. M-B instructed me to use only National Branded Truck Stops. I asked, "like pilot/flying J"? The rep said,"yes". i had already spoke with Pilot/Flying J. They said, "our diesel contains a minimum of ten percent biodiesel" As per required by EPA all diesel contains at least five percent. some states fifteen percent.
From Mercedes lips to your ears...
my advice...change oil every eight thousand. Un-burned fuel is returned to the crankcase, thus contaminating your lube oil. Bio has a higher flash point than fossil. Most of the bio will not ignite. Also keep close on oil level, it can increase crankcase capacity
This has been a known issue since 2010 on the diesel truck/car sites. We just deal with it and put on double fuel filters to keep the crude out of the pump and injectors. The crude comes from the your fuel tank after using regular fuel and than Bio-fuel. Bio-fuel happens to clean real real good and the crude is stuff that is left in your tank from regular diesel fuel.
On my wife's 2011VW Jetta TDI; we received a letter from VW stating that the warranty would be honored using B20 fuel in IL. Reason IL mandates a certain percent of the fuel refined/sold must be B20.
"No unburned fuel is not returned to your crankcase it is returned to the fuel tank."
The way unburnt fuel is returned to the crankcase is due to the regeneration cycle were fuel is used to burn off the diesel particulates that are captured in the Diesel Particulate filter. When the filter reaches a certain level of containment and the deferential pressure switch senses a restriction, the regeneration cycle is started. The way this is accomplished is to use diesel fuel that is injected into the exhaust cycle and the DPF temperature is raised between 1200 and 1450F. These temperatures will reduce the particulates to ash. During the exhaust cycle some fuel can enter the crankcase and cause your oil level to increase.
On my Ram I monitor the oil quality and in 92,000 miles I have always had less than 1% of fuel dilution to the oil in 7,000 miles. My truck will regenerate ever 300 miles or so when I towed our 5er. My EGT gage will raise to 1450F for 20 min's or so as the filter is cleaned.