If you own the business, then it is no problem. Vehicle maintenance is not a red flag unless you start spending 10's of thousands on one car. With receipts your fine.
First you have to get audited, Have you been audited before?
One line item increase on your tax return should not raise any eyebrows.
If you are not the owner of the business, that is the ethical part. I would terminate your employment if you tried to expense that.