Can a company not reimburse you for traveling if you paid for the gas but used a company car?

I did over 700 miles of traveling roughly and spent my money in her car while she was on vacation for two weeks. Doing traveling that I was scheduled for, not asked to do. I went to fill out the mileage form and my boss said she had talked to my DM and she said I couldn't claim mileage because it was in her car. None the less, I still drove, and still used my money. That was over 100 dollars in her car, that they're refusing to give back to me. I'm just wondering about the legal aspects of this because I would like to possibly sue if it is illegal like I'm thinking it is. I live in Colorado if that makes any difference.
I did over 700 miles of traveling roughly and spent my money in her car while she was on vacation for two weeks. Doing traveling that I was scheduled for, not asked to do. I went to fill out the mileage form and my boss said she had talked to my DM and she said I couldn't claim mileage because it was in her car. None the less, I still drove, and still used my money. That was over 100 dollars in her car, that they're refusing to give back to me. I'm just wondering about the legal aspects of this because I would like to possibly sue if it is illegal like I'm thinking it is. I live in Colorado if that makes any difference. She uses a company credit card to pay for gas, then sends in receipts. I didn't keep receipts because I figured I could just claim mileage.

Does "she" work for the same company?

How does "she" normally fill the gas tank? Does she pay or does she use a company gas card?

Yes (though most won't). If so, then you can claim that expense as a tax deduction if you itemize.

You should have gas receipts and time records to show that you spent time on the clock doing her driving.

They should reimburse you for the gas provided it was what they told you to do and you weren't screwing off doing personal errands on the clock.

Use Yahoo maps or Google earth and track your driving and prove to them that it was legit.

Sorry to say, but, in this day and age, corporations have the upper hand in everything! You can try to get reimbursed, but I seriously doubt if you can accomplish it! I don't think there is an attorney in the entire country that would take your case! At over 200 dollars per hour, which is somewhere very near what attorneys charge, you would be much better off just to forget the $100. you spent on gas and chalk it up to experience and not do it again unless there is a company credit card provided for the gasoline and any maintenance/repairs on the company car while it's in your possession.