對不起，是我看錯了, IRS Medical 也是20 cents

Beginning on Jan. 1, 2019, the standard mileage rates for the use of a car (also vans, pickups or panel trucks) will be:

• 58 cents per mile driven for business use, up 3.5 cents from the rate for 2018,
• 20 cents per mile driven for medical or moving purposes, up 2 cents from the rate for 2018, and
• 14 cents per mile driven in service of charitable organizations.

原因應該是商業用車可能是專用商業用卡車或者麵包車，價值高費用。medical用車估計就是民用車兼顧偶爾用medical，價值低一些。