4.8%? Which rental company was that, i'll avoid them on principle. And it is possibly illegal, the charge is not supposed to be used to generate a profit, only to cover the costs of accepting CC payments.

The larger rental car companies don't charge a CC fee at all, and the two lower end of the market companies I've used charged 1.9% and 2%.

For most hotels, cafes and retail outlets that charge a CC fee its in the range of 1.5 - 3% for Visa and Mastercard, Amex usually charged a bit higher since the merchant fees are apparently higher.

The highest CC fee i've seen was 10% in a taxi, some taxi companies charge a $2.50 flat fee for paying with a card (including debit cards) regardless of fare. Obviously the flat fee is better on more expensive taxi rides, but a complete rip off on shorter journeys. Just pay cash for taxis, or avoid them entirely.