SAVE 20 CENTS PER GALLON: Amazon Prime members can save up to 20 cents a gallon at BP and Amoco on Fridays. Here’s how to claim your fuel discount . It's easy to forget all the benefits you get with Amazon Prime . Like, I somehow always forget that prescription and gas discounts are included with a membership. And, as the proud owner of a V-8 GMC Sierra, that's the kind of information I need to keep in the "relevant" file. I've literally seen regular gas (not even premium) as high as $4.30 per gallon in North Carolina, which is ridiculous. So, whenever there's a way to make filling up this truck even slightly cheaper, I'm all over it. Mashable Trend Report If you have Amazon Prime and you aren't using its fuel discount yet, you're basically throwing money away. By linking your Prime account to BP's "earnify" app (which is completely free to set up), you get a flat 10 cents off per gallon every single time you fill up at a participating BP, Amoco, ampm, or Thorntons location.…