This oil does exactely what its supposed to do! Engine is quieter, runs smoother, and stays cooler. Unfortunately for me, my car calls for 5w30 and this is 5w40, thus my avg. mileage, after three tank refill periods, did go down by 1 mpg. (1995 Buick Roadmaster 350/Lt1 w/34000, yes only 34,000 miles). Combo city/hwy 15 mpg to 14 mpg. Oh yea, Walmart will probably be the best price around, however they sell it higher in the stores than online (and they will not honor/price match any online prices or ads, even if you choose the ads for that particular store). So, do their online ship to store option, you will have to pay online but at least you get the discounted price. Plus go to the Shell Rotella site and sometimes they offer a $5 mail in rebate offer to, makes it 14.22 a gallon, not bad!