There is currently a long posting/thread on a new discount diesel program over at the IRV2.com forum...go take a look at that, several have said it has a lot of promise, but involves access to a checking account/debit-like setup. Said to be particularly great discount at Loves Truck Stops, something like 35-40c/gal. Other than that, I use GasGuru to find prices, and have a 50gal aux tank in bed. Easy to find 10-40c cheaper diesel than the Pilot/FJ/TA/Petro stations. Lots use GasBuddy, but I am finding it too much advertisement/askings for getting their credit card. I also look for WalMarts/Sams that sell diesel and check on GoogleEarth first before trying to get in with the fiver.
2016 Tiffin 40 QBH
2015 38RSSA, traded
2005 TK3 #1869, 10 yrs of memories,
2017 F450 KR--one more Ford is it
2009 F450 4x4-died; 2010 F450-retired