(KMDL-FM) - If you have Amazon Prime and need to fill up your vehicle today, you could possibly save some big money. How the Amazon Prime Gas Discount WorksAmazon Prime is once again bringing back a big promotion for one day only. It's where Prime members can get $1 off per gallon of gas (up to 35 gallons) at participating BP, Amoco and ampm gas stations today, on Friday, Oct. 3. The $1-per-gallon offer breaks down as follows:Earnify's standard 5-cent discountAmazon's 5-cent Prime discount90-cent promotional bonusWhat Happens After the Promotion EndsAfter the promotion ends today, Prime members can still save at the pump. Amazon Prime memberships run $14.99 a month or $139 annually.