At the places that have the higher discounts. True enough, those are becoming fewer and farther between. Many have 0.000 discounts, some have just 0.002 of a discount (which comes to a nickel total off a 25 gallon fillup). The discounts in IL are still decent, but nowhere near what they used to be. In Illinois, at least currently, they're all but gone. The 40 and 50 cent discounts all seem to be gone, tho I haven't looked at today's PDF all that closely.
For me, at least, in a van and getting 20-25 gallons per fillup, I can take 6 cents off whatever discount there is for 25 gallons, and 7.5 cents off for 20 gallons, because of the $1.50 Comdata fee. The free shower is still worth 20 cents a gallon on two 25 gallon fillups. So the fuel at another truck stop would have to be more than 20 cents cheaper. If I did it as 20/20/20, then the 50 gallons would cost me $3.75 in Comdata charges, and the free shower would make the overall discount closer to 13 or 14 cents. Still a better deal, for me. Not so much if I'm buying more than 50 gallons at a time. At that point you'd have to go with the cheaper pump price, since you'll get a free shower, anyway.