The 300 D Mercedes-Benz is the most reliable car i own. I have a 1978 and it has over 300,000 miles on it. It has a 5 cylinder 2.5 liter engine. And it runs like I just bought it a week ago. The only things I've replaced are the radio and the gas filter. Everything is in tip top shape. It's gas mileage is also great. It gets 30 miles per gallon. It is a diesel so it isn't the fastest out there, but if you treat it right this car can last you a lifetime. It is comfortable also.
I recommend this car to anybody that wants a car that they can keep for a decade or two or three.