What motor oil is best for fuel efficiency?

I have a 2007 Chevy Cobalt. What type of motor oil will give me the highest fuel efficiency? I would imagine synthetic 5W-30, but does the oil really matter?What motor oil is best for fuel efficiency?
Motor oils change viscosity with temperature ei: cold climate =thicker oil, hot climate =thin oil. This can effect fuel usage due to extra friction from the oil itself. The manufacturer will specify a viscosity rating based on climate temp. PS too low viscosity can cause engine damage.What motor oil is best for fuel efficiency?
Correct depending on the area your live and drive your car in that will have a major effect on what kind of oil you should be using. http://www.savefuelmilage.com Report Abuse

Do not put a NON-emission oil in an emission equipped car! For one thing DUH!!!!! These oils have compounds in them that when passed into catalytic converter will cause damage and in turn $$$.


Use what is recommended by the manufacturer. Yes, It REALLY matters. Otherwise your manual would tell you to pour in which ever oil you find most appealing.





P.S. IT FREAKING CAME WITH SYNTHETIC OIL!!!!! READ THE MANUAL FOR CHRIST SAKE!
Stick with what ever the manufacturer recommends. Don't experiment with this important fluid. You could cause serious damage to your engine.
530 is what is recommended, the synthetic can improve that a little more.
Royal Purple. the XPR is for non-emmision vehicles only, just use the atandard R/P. Best Synth out there, no question.
synthetic oils flow better and run cooler. I gained about 2 miles per gallon switching.





Mobiles very good.