I usually buy fuel at the J, cause they give me free showers.
Being in a cargo van I'll never buy 50+ gallons in one whack. It's more like 20 or so, 25 max (26 gallon tank). Unlike the others, at the Flying J the gallons keep on adding up, 15 here, 20 there, 20 more down the road, and every 25 gallons purchased I get half a free shower.
I don't fuel off Comdata because of the transaction fees. Only buying 20-25 gallons at a time, the few cents per gallon discount I'd get at the Petro, Loves, TA, doesn't offset the transaction fee for using the card, much less getting a few pennies saved here and there on fuel and then having to lay out nine bucks for a shower. Twenty gallons, save 5 cents per, that's just a buck. I just do a single direct deposit from my Comdata account to my bank once a week, then run off the debit card. Besides, I can fuel at the car or RV islands and not have to deal with the pricing at the truck pumps, while still using my Flying J Frequent Fueler Card. Most places, Comdata isn't accepted at the auto diesel pumps.
I get the 45% at POD, and I just leave it there on Comdata. Then the settlement goes onto the card on Friday, and that's when I usually initiate the direct deposit. The deposit happens the next day (Saturday), but my bank is retarded and won't let me have access to it until Tuesday, not until the computers have done their thing overnight on Monday night. Apparently, their computers have banker's hours, too.
Once in a while, if I'm near a branch of my bank, I'll go ahead and do a Comcheck, cash it at the bank, then before they even give me the cash I'll hand them a deposit slip and deposit the cash. If I deposit the check, it's Tuesday, of I cash it and then deposit the cash, it's immediate. I know, retarded. Reeeeeejuhns.
So, I just try to make sure that I have a minimum of $750 in the truck operating account which will cover up to 5000 miles at $3 a gallon, which is the absolute most I'll likely ever drive in a week. And even on Friday when I do the direct deposit, I'll usually leave a couple hundred on the card, just in case I need it over the weekend.
This system works well for me. One of the benefits of not buying fuel on Comdata is that I have a better record of what the trucks spends, on everything. Whether I'm paying myself or buying fuel, there's a banking transaction record of it out of the truck account, which is also tracked in Quicken. I can quickly find out how much was spent on what, and when.