Nearly two-thirds of motorists feel awkward about asking passengers for petrol money in return for a lift, a survey has found.
Some 63% of people feel this way - with men more likely than women to ask their passengers to stump up some cash - insurer Admiral found.
Nearly a third (31%) of male drivers said they do ask for contributions towards their costs, compared with just over one in five (21%) women.
Siblings, parents of children's friends, colleagues, friends and neighbours are the least likely to offer money for a lift, drivers said.
Some 72% of drivers giving lifts claimed that even their closest friends do not offer any petrol money in return.
Over a quarter of drivers (27%) said they had fallen out with somebody who did not pay their way, the survey of more than 2,000 people across the UK found.
Sabine Williams, head of motor at Admiral, said: "Most of us have given or received a lift from someone else in our lifetime and many of us do so on a regular basis, so it's interesting to see that we don't seem to have an established set of social rules when it comes to offering or accepting petrol money - And that it's actually causing some people to quarrel."