Please see the Chamber's post on the increase to the standard mileage rate. (Here). Most employers are concerned with the business reimbursement rate, which goes up to $0.575 per mile effective January 1, 2015.
Here's a quick spiel on the significance of the standard mileage rate:
Employers in California are required to reimburse employees for reasonably necessary expenses incurred in connection with their work via Labor Code section 2802. Expenses associated with personal use of their vehicles are included within 2802.
Most employers pay the IRS reimbursement rate. It is not mandatory to do so. But how do you calculate how much oil, tires, and brake shoes that an employee's business trip will consume?
Right, you can't. That's why it pays to pay the standard rate.
Employees may argue that the standard rate is not enough. But it's their burden to show that their actual, reasonably necessary expenses were worth more than the standard rate. And it's going to be hard for them to measure the "actual" necessary costs of operating a car for a 30 mile trip.