Sorry Ladyt25, I must have missed your post.
Luxembourg is still the cheapest to refuel.
The St. Gotthard Tunnel is free.....but do it on a Sunday if you can,- when there are hardly any lorries on the road.
The route mentioned via Frances Belgium, Luxembourg, France again, Switzerland and finally Italy is the cheapest. (Only motorway charges in Italy.....and worth every penny! - The Autostrada is not for nervous drivers though, as the lorries are always no more than a metre away from your back bumper. When you leave a gap between yourself and the vehicle in front, someone fills it!
We do the journey four times a year. Until this year we have done it with our two dogs, but sadly we lost them both recently. Six years ago we bought a motorhome to do the travelling. Even though we have a big Land Rover 4x4 in the U.K. the journey here to Kriti is much nicer in the camper! You can do Camping on Board with ANEK from Ancona and Bari. It means you can stay in your van with your animals. You get an ehu, clean showers and loo, and a ‘key’ to the rest of the ship, so you can use all the facilities. I understand it works out cheaper than having a car and a cabin, as friends of ours who have a house on another Greek island, and live there six months of the year, have bought a small motorhome to do the journey.
They use their van to have a holiday for a couple of weeks on the way out to Greece and on their way back to the U.K. We have tended to come straight here and back in the past, (6 days each way from the south of England .....using the Channel Tunnel and spending a night on the Peloponnese each way). This year, as we only had the cat with us, so we had a brilliant holiday in France for two weeks on the way out. - Reims and the Cathedral, the old part of Troyes, Champagne, Burgundy, the Jura etc, then a week in Switzerland/Italy/San Marino, finishing off with a week in the Peloponnese.
Of course it all depends in how much time you can spend travelling, but the journey is best done as part of a ‘holiday.’ Our son is flying out from Leeds on Tuesday to see us. If you are looking for ‘cheap’ then that is the way to do it, but if you want to bring your dog, then the drive is easy. The only bit I don’t like is on the autostrada in Italy!
Finally, Camping on Board is VERY popular now. The French, Dutch, Belgians, Italians and even many Germans use Ancona if they can. (With Minoan they offer Camping in Board but don’t let you stay in your van. They give you a cabin instead.....so not so easy with animals, (especially if people have big dogs), even though it is a pet cabin. You can also only book Camping on Board with both ANEK and Minoan if you have an ‘authorised camping vehicle. - You cannot sleep in your car!
If you plan to do the trip regularly, it would be worth you considering buying a small van like a VW T5. You could then use it in the U.K. as an ‘every day vehicle’ but also have the benefit of a good vehicle to travel to and from Kriti in. We have a 7.5m motorhome and it would be more expensive on the ferries than a smaller van, but it is still cheaper than having a car and a cabin!
Warning.....there is no Camping on Board from Piraeus to Kriti, but there has never been a problem with us leaving our animals in the van for the 9 hour overnight crossing. - In fact they are usually more ‘refreshed’ the next morning than us! I am not sure if it is allowed.....but the Greeks do it all the time.