If youre down south where it dosent get cold, you should be fine! dump the sludge in and go just as sniper said. I fill up at cardlock truck stops for the business so just pop the nozzle in while i am filling diesel tanks. Not sure how much truth is in it, but ive been told the cardlock/truck stop def is generally always fresh due to the high useage by semis. Def has a shelf life of i believe 6 months, so if youre buying the jugs make sure its within date! and potentially staying within that date for the time it'll be in your tank. I was warned during my emissions issues that def quality is HUGE on these 21+ trucks. Aparently the computer can detect when the juice has gone sour, and rather than choking it down it'll just throw you into de-rate and make you drain tank/re-fill. Sniper also makes another good point, you only hear about all the people that have issues never the ones that are happy. since 2012 ive had 6 emissions equipped/def trucks and until this one have never had an issue. Having said that all 6 of those were deleted within 20,000km. FYI if you live in a cold climate, keep the tank at half for the winter, tank heater isnt capable of thawing the entire tank and if the ultrasonic sensor cant get a reading quick enough it'll also throw you into de-rate. De-rate is fun.