Thor Forums

[The Gritz Carlton]

I spoke with a rep for Blue DEF a few years ago when I bought my 2011 GMC 2500HD (first year for light truck requirement). He said the stuff is sensitive to heat and has a short shelf life...do not stock pile. I've had two incidents over last 8 years with "DEF-Poor Quality" lights and threaten to restrict MPH or shut down. Make sure you buy it at high volume truck stops or other truck oriented businesses. I wouldn't use the bulk at the fuel pumps...only buy the sealed jugs as they are dated and you know they haven't been watered down (yes, they do this). It's a matter of opinion and experiences, but I don't keep DEF tank full on my new F550 Chateau. I will add to it a bit to keep it fresh and only fill it if I know we're doing a 10 day+ road trip. If it sits for extended period, I'll drain the tank and refill it with fresh. Bad DEF will eventually cause clogging of your particulate filter resulting in expensive filter replacement. Motorhomes are the biggest victim of this as they don't get driven much and the stuff goes bad. FYI...it is made with pig pee!!


In Turner's case above, the math shows he is driving over 20,000 miles per year which will keep the DEF reasonably fresh. If you're not blowing and going like this...keep your eyes on it.