I have been advised to rent a diesel auto for fuel economy. How prevelant are diesel pumps at service stations in southern Portugal, southern Spain and Gibraltar? How much is diesel as opposed to regular gas? Was this information wise?

I toured Portugal by car for 3 weeks in September. The rental agencies had diesel cars, but not many. I drove a gas-engine Fiat. Diesel fuel was available at every filling station I stopped at all over the country (ALL the trucks and buses seem to be diesel), even in small villages. Sorry, I don't recall the price. We paid about $4 US/4 L for gas. The car got around 40 mpg, so this wasn't as awful as it sounds. Don't have any info about the rest. Might be more economical to choose by rental fee.

Good question, but let's look at Italy and France as well. I've thought about renting a diesel car also, but envision being in some small hilltown, low on gas, and no diesel available. Is diesel available in all places in Italy and France, and am I being too worried?