[2023] Engines are very scarce.

So I checked the xml.

A20 cntCar03SedanDamage1Master

A20 cntBusSchool

A20 cntArmyTruckOpen

A20 decoCarMotorFlat


Keep in mind that there are some sub-vehicles that also get the data pulled from the master. Like the Army Truck Closed just references the same rate that is in Truck Open.

Now let's look at a21...
A21 cntCar03SedanDamage1Master

A21 cntSedan01White

A21 cntSedan3Wide01White

A21 cntFrontCrumpledSedan01White

A21 cntMinivan01White

A21 cntMinivan3Wide01White

A21 cntSUV01White

A21 cntSUV3Wide01White

A21 cntPickupTruck01White

A21 cntSemiTruck01White

A21 cntPoliceCar01PickedLockBonus

A21 cntPoliceCar01AlarmUnlocked

A21 cntFireTruck01White

A21 cntBusSchool

A21 cntArmyTruckOpen

A21 cntFarmTruckClosed

A21 forkliftWhite

A21 forklift2White

A21 decoCarMotorFlat



So in a21 there are a lot more varieties of vehicles, and they are all essentially at 25% drop rate just like they were in a21, but it's calculated a bit differently.
Instead of flat 25% drop rate, it's a 50% drop rate with a 50% chance of getting nothing.