Mileage - when can be claimed

I have a question about when mileage can be claimed. I normally borrow my other half's car when I have an incidental travel to a company event and I claim the mileage after that. However there is an upcoming occasion where I won't be able to take partner's car. If a friend gives me a lift and I pay for the fuel, can I still claim mileage for that trip from my employer?

Hi RiBar,
We would need more details to help with your enquiry or you can contact HMRC for advise:
Income Tax: general enquiries
Thank you. 

Hi, I'm not HMRC Admin but what your employer pays you is a decision/discussion between you and your employer. However as mileage allowance payments do not apply when you are passenger in a vehicle, any payment they do make will be taxable on you as earnings. https://www.legislation.gov.uk/ukpga/2003/1/section/229