I have since 2004 Renault diesel cars. A Renault Symbol (like Cleo, but with a 500 liter boot), with a 1500cc 85HP engine and a Renault Megan with the same engine..
They are very reliable, fuel consumption BETTER than 5 liters/100Km (real average: 4.2l/100Km for the Symbol and 4.8/100Km for the megan), BUT with manual gear.
The new Renault Fluence is with the same 1500 engine, delivering 110 HP and DUAL clutch Robotic gear.
Also the more expensive VW Jetta or Passat with the new 1600 Diesel clean engine will do.