Take a look at the Previous-function and use it in a resident load. Make a Resident-load on the initial data and remember to sort your data.
// Get data
LOAD Date, Vehicle, Odometer
// Resident load, where you sort the data by Vehicle and Odometer AND uses the Previous-function to calculate the difference (trip)
,if(Vehicle=Previous(Vehicle),Odometer-Previous(Odometer),null()) AS Trip
ORDER BY Vehicle, Odometer;
// Drop initial table
DROP TABLE Initial_load;