When my w walked out last year she "borrowed" the car saying she'd buy me out, then she failed to get a loan on her own and contacted me to say she didnt want maintenance but did need the car, had a claim as she paid off the finance (ignoring who'd paid all the installments of course).
Since I didnt want to add a huge impediment or impact s with education/trips etc I worked out how to get another one.
Who's car is it? Is it registered to you?
Certainly if it's 'your' car with W using it taking it to go see Om seems to be somewhere a boundary may definitely be appropriate.
M:44, W:46, S:10 M 13 years, T 15 BD:23/7/2014 W/S Moved to MIL: 23/7/2014 My new place: 21/11/2014 W/S back to flat 22/11/2014 W coming closer, talking 4/2015 Piecing 5/2015 Moving in again 6/2015