Yeah, I was doing the same thing. Working for a large corporation, trying to climb the ladder- ended up using my personal vehicle for work- got used to doing it not asking for mileage reimbursement or anything (driving a tuner car getting 30+ at the time) when eventually on my way dropping something off at a store for work- I got rear ended on the highway causing me to lose control and total my car.
Long story short- I ended up quitting because my car was totaled and they didn't want to help me out at all for a new vehicle, when 70%$ of my day was spent on the road...
Went to a smaller family-owned company, and LOVE the amount of help and reimbursement.
Take care of your vehicles, don't use as means of work- it'll cost you more later.