Coin denominations of $1 and maybe $2 last longer than paper bills. I know at one point the US gov't pushed dollar coins since it wouldn't have to print so many $1 to replace the ones that get worn out so quickly.

Personally, whenever feasible, I use the dollar coin. When I make withdrawals at my bank I will request a few dollar coins instead of single bills.

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2014 Mazda 3 GT: Ø Consumption: (click for details)