Everyone who has had thier oil changed. Did the dealer use 5W-20 for the oil change? Just had mine done last friday, and according to my receipt, they used 10W-30. We get free oil changes for the first year, so it's not like I paid for it, but just wondering if it had any effect on my gas mileage on my trip from San Diego to Fallon, NV where I got a best of 28mpg. Previous best in my Caliober was over 30mpg. Just find it funny that the dealer would put in 10W-30 when the owners manual calls for 5W-20.