You got it backwards, 5w-30 is thinner than 10w-30. Also the 5w is for when it's cold - the 30 is for when engine is warmed up. I wouldn't recommend using oil that the manual doesn't call for due to damaging the engine which would negate the savings in gas, however if you are wanting to save gas, you want the Xw-20 or lower.For example, using 10W-30 motor oil in an engine designed to use 5W-30 can lower your gas mileage up to 2%. The thicker the oil, the harder it will be for the pump. This adds to parasitic horsepower loses.
Agreed, use the recommendations by the owners manual for the long life of your engine performance.You got it backwards, 5w-30 is thinner than 10w-30. Also the 5w is for when it's cold - the 30 is for when engine is warmed up. I wouldn't recommend using oil that the manual doesn't call for due to damaging the engine which would negate the savings in gas, however if you are wanting to save gas, you want the Xw-20 or lower.
I noticed you usually include "at Shell". Are you in an area that there is a real difference from brand to brand?$3.69 at Shell.