Here is the information that you needed.
Today is 7/23/2008 and the prices of fuel in Portugal and Spain are as follows:
Unleaded 98 1,589 1,275
Unleaded 95 1,503 1,078
Diesel 1,399 1,075
Do you wanna know what's the reason for this HUGE difference?
In Portugal we double tax the liter of fuel, meaning the total tax that you pay in 1 liter represents 59%.
There is de IVA tax (21% for all products) and then is the tax over fuel products which I don't know the exact amount.
So this has a name:
We are being robbed by the government, pure and simple.
So if you come to Europe, rent a diesel car - as you can see in Spain you don't get any advantage but in Portugal, yes; furthermore, diesel engines polute less, are silent, are more powerful, more reliable and more economic than the gas ones.
That's why there have been a huge demanding in diesel cars in the last decade.
Despite of being expensive, if you do many miles per year, you'll get the benefit compared with a normal gas car.
Another important tip:
Try to refill your tank in a supermarket gas station by keeping the ticket of what you bought; at the end you'll obtain a significative discount per liter
One more thing:
Things here are much more expensive than in the US so I was told by my girlfriend who lives in Rochester, NY.
The only thing that is less expensive here is the milk.
You must also pay atttention to the currency - multiply the prices in Euros per $1.66USD
Take care and have fun