Car sharing is fun and much cheaper than European rail, writes Eva Buzo.
A backpacker's life is about trade-offs. There are delicate calculations.
"If I sleep on this grassy knoll outside Madrid station for four hours instead of getting a hostel bed, I can splurge at the famous tapas bar in Barcelona."
Money is for experiences. No one ever wrote home about a hostel bed.
This is why backpackers need to be introduced to Mitfahrgelegenheit - don't let the name put you off, it simply means "carpooling" and is the way many people get around Europe without paying exorbitant European rail prices.
With Mitfahrgelegenheit, travellers pay on average a fifth of what they would pay for the train - as long as they're willing to get there in a car full of strangers they met on the internet.
Perhaps the cautious types would be slightly alarmed by this suggestion, but for backpackers, strangers are just about all you have for company during those months on the road.
And they're a vital part of the whole experience - as long as you keep telling yourself "a stranger's just a friend you haven't met".
The system started in 2000, when three student entrepreneurs at the University of Wurzberg, wanting to save on travel costs, used a university website to pair-up with fellow travellers.
Within a year they were able to launch the national website with the name Mitfahrgelegenheit.de. Users can enter their departure point and intended destination and access options, the cost, and the mobile number of the driver. They then contact the driver asking to check if there's any space left, arrange a pick-up point, and that's the game.
For example, the Hamburg to Cologne trip usually provides 15 or 20 options daily, charging an average of €20 ($32). The same journey by train would be €100. Cologne to Paris offers 10 to 15 daily options at about €32.
All drivers are required to register their number plate and driver's licence on the website. There is also a complaint system, which can lead to drivers being banned from using the website.
The most extensive Mitfahrgelegenheit network is in Germany, but the system is used by travellers in Spain, Italy, France, England, Switzerland, Austria, Greece and Poland, transporting two million people a month. The website also boasts that it has been responsible for 16 marriages.
"I've used the system over 100 times," one of my new buddies, Brigette tells me as we drive from Hamburg to Berlin.
"I made one of my best friends on a nine-hour trip from Bordeaux to Hamburg."
"One time I had this weirdo telling me to watch out for all the birds when I was driving to Amsterdam from Hamburg, but there weren't any birds.
"I considered leaving him at a petrol station."
So now we shoestring travellers have yet another trade-off.
Pay more for the predictability of the train or less for the unpredictability and adventure of unknown travel companions.
Put it like that and for many backpackers the balance tips in favour of Mitfahrgelegenheit.
After all, strangers make good friends, and weirdos make good stories.
Further information: The English-language version of the website is at carpooling.co.uk.