Technically you can get a tax benefit. If you are the primary operator and it is your own personal vehicle, you can collect from the passengers a reimbursement of your operating expenses. If what you charge is more than your expenses, you have to treat it like a business (like taxis/limos do) and determine profit/loss, but if you just charge your operating expenses the IRS explicitly says you do not report it as income as it is just recouping your expenses.
There is a safe harbor provision that you can collect up to the IRS mileage deduction (about $0.565 per mile) in aggregate (i.e. 4 passengers = $0.565/4 = $0.14 each) as reimbursement for your expenses without having to assess profitability.
So if you operate a mustachian car that costs maybe $0.25 a mile to drive, and you're willing to do all the driving, you can charge your colleague up to $0.565 and essentially fully recoup your costs PLUS earn $0.30 a mile tax free. Not a whole lot, but if you have a 10 mile commute each way you're looking at $1,500 tax free bucks a year in your pocket.
