We will be renting a car this summer in Italy in July. If we have a choice, would it be best to have a car that uses unleaded gas, or would diesel be a better choice? Is there a difference in price/availability? Thanks for your help!
Both diesel and unleaded gas are available just about every where. Diesel powered cars seem to get better mileage.
Gas runs about fifteen percent more than diesel. The smaller, cheaper-to-rent cars tend not to have diesel engines. Thus, the fuel cost and mileage may not be significant in the total vehicle expense. I take the cheapest car I can find and live with it. When I've tried to retrospecively renoodle it, I've never found fifty bucks worth of difference - - and that's at a rate of thirty days and about three thousand miles. I can't picture ever having seen a station that didn't have both. Watch your nozzel, the filler hole ain't idiot-proof - - I once gave a diesel a good squirt of gas before realizing what I'd done. Gasoline has octane ratings 95/98 on the handle or pump (sometimes both), diesel doesn't.
Diesel is a bit cheaper per litre and you get better mileage. A compact car should get you about 1000 km or more out of a tank of diesel! Diesel cars are usually a bit more expensive when purchased and this is reflected with the rental prizes in some rental agencies. But not always! We found a quote with autoeurope for a Fiat Bravo (a perfect size for the 4 of us + luggage) with a diesel engine that was better than comparable sized gasoline cars.
And be sure the attendant knows which one you have when you gas up. My wife got a guy that insisted our diesel vehicle took unleaded gas. I've caught a couple of guys reaching for the wrong nozzle also.
I have rented diesel cars in Italy, Spain and France and have found them to be cheaper in the long run, as far as consumption goes. By carefully shopping around, I have never paid more for the rental for a diesel model. Diesel was easy to find everywhere in Italy. Slowtrav has an excellent section on gas and driving in Italy:
http://www.slowtrav.com/italy/driving/gas.htm