Asking University to reimburse renting a car I'm shortly going to a conference which is held at a centre pretty much in the middle of nowhere (or, to be more precise, in the middle of a hiking region). The suggested way of reaching the destination is by taxi, and the public transportation is nearly non-existent. 

Me and a group of other junior researchers (PhD's and PostDocs) have decided to hire a car to make transportation easier and to take full advantage of the attractive region. Split four ways, the cost is quite affordable. 

I am wondering whether it is acceptable to ask my university for reimbursement. We have an allowance for travel expenses, so there is certainly an available source of money. However, I have two problems with making the request. First is a moral one - can I ask the university to reimburse a car which we'll partly use for our own enjoyment? Second is more practical - is the university likely to agree? Will they be able to process the kind of receipt car hire company will issue? How do I explain that I paid exactly 1/4 of the quoted price?
Yes, this is acceptable. 

At many universities, adding a few days stay at your conference location in a far-away country (using your own accommodation arrangements) is allowed and sometimes even encouraged. Especially when this allows you to take cheaper flights. This would be something similar, using the car because it's required anyway, and adding a few extra recreational km you'd pay for yourself. 

Renting a car might be an issue for some European universities, as they have rules to encourage public transport usage. The 1/4 share of the car is something you'll have to discuss with your administrative staff. They might want to reimburse 1 person for the whole thing, or split it over multiple projects. Just ask to clarify, they'll also be happy to know exactly how and what they're reimbursing.