I thought I'd do a cost benefit comparison between these two oils as a number of us are using the 5-20W. I recently did my first oil change at 1700 miles on 2011 SR5 and used 5-20W mobil 1 because it was sold in bulk 5 qt at walmart. I'm now currently at 4400 miles. I've noticed mpg has dropped about .5 miles on the display as well as when I do a calculation based on fill up. Given the present cost of gas I wanted to crunch the numbers and see if I was coming out ahead by using the cheaper 5-20W. Based on a planned 5000 mile change interval the answer is no
Assuming gas at $4 gallon
with most of my driving on the fwy I've averaged 20 mpg
-For every 20 gallons ($80) I'm losing about 10 miles by using the 5-20W
-There would be approximately 23 fillups between oil changes which equates to roughly 230 miles lost.
That is an additional 11.5 gallons of gas at $4 a gallon or $46
Toyota 0-20 is $8.50 X 6.5 =$55.25
vs 5-20W 5 qt at $26 + $6 (1.5qt) = $32
Up front savings with the 5-20W is $23.25 but that will be negated by poorer mpg and you get the peace of mind of knowing that you used the recommended 0-20W intended for the car. Again my driving is mainly highway so you may experience even greater loss of mpg with stop and go.