I've had this problem with a Freightliner a few years ago.....
I wouldn't worry unless the temperature gets to 10 * F or below... . than I'd start to treat the fuel and would do it no matter what until the temperature was going to stay above 10*F... .
Go to a local truck stop... there are several brands of chemicals available for this... buy a 1/2 gal container... I've even seen it at Wal-Mart... . In fact if you buy your fuel at a local truck stop, they are going to have blended or treated the fuel and since they go through tanker of the stuff... you should be ok. .
Follow label directions... . This is not a big issue... .