Using heavier viscosity oil to increase fuel economy?

[jamescartagena]

Has anyone tried using a higher viscosity oil and saw any mileage differences. I've taken the advice of Louis LaPointe's article on www.lubedev.com and switched the 5w30 oil that my Saturn had that I bought in June and switched it to 20w50 (Walmart SuperTech for testing right now) and my gas mileage has increased. Over the past 4000 miles on the 5w30 the best I could get was just under 38 mpg. With 20w50 over the past 1500 miles, my gas mileage has increased to 40 mpg. Pumping up the air in my tires to 44 psi, this week's mileage is 41.2.

I haven't changed my driving habits and drive this vehicle mostly on the highway. It doesn't burn or leak any oil so I didn't switch to the thicker oil for that and I haven't noticed any power loss due to the heavier oil.

I've tried the same thing in my F150 but instead using 10w40 and achieved the max mpg I got with synthetic 5w30 the first two weeks after changing the oil (22 mpg) . And this was having the cruise control on 64 instead of 59 where I usually keep it. Hopefully I will change to 20w50 this weekend if time permits and see what results I get.