No no you can't use 38.5 mpg that doesn't work, even someone like me can drive 500 miles to VA non stop and get 48mpg without fancy stuff. You drive city roads all the time and keep the speeds down to get 900 miles per tank, that's not going to happen if you get on the highway and drive non-stop at 65mph. Try it, I'm sure you have already, in that case you'll get something in the 600's range per tank. I average around 700 mi. on a tank on the HWY and a little better for the City. My Fuelly for HWY is 79% and City is 21% so most of my driving is on the HWY.
38.5 is what Ford adjusted the MPG rating as people floor the car and drive terrible in relation to hypermilling and then they complain they are not getting the ratings. Anyone who tries just a little bit to drive better will be well into the 40's mpg.
Your loss is $10459 - ($3582 x $2.52) = $1432 for using Premium fuel per year or about $7281 in 5 years 1 month's time. This is way wrong, somebody got confused, the right answer is $1034 Total or $200 per year.
You get bonus MPG numbers for bragging rights by paying this premium, you NEVER make out driving Premium vs regular in savings. When I first started out in 2012 with gas at $4 per gal and lower MPG's there wasn't much a difference in cost between using Reg and Prem with the improvement in MPG's, but now with cost of gas at $2.40/ gal and getting much better MPG's it isn't cost effective now. I'll say It again "This isn't about Cost for Me", it's about getting the best possible MPG's and what's wrong with Bragging Rights? Don't you have the best distance of 37mi. for a HVB charge? Good Job!
Here is a Link to My Fuelly Dash: http://www.fuelly.co...ptjones/163299 and here is a Link to Fuelly 2013 CMAX Hybrid SEL average MPG of 38.5 :http://www.fuelly.com/car/ford/c-max/2013?engineconfig_id=341&bodytype_id=&submodel_id=1203
Raja you need to check your Math.
$10,459 is the Total Cost of running Premium since New. I gain 2 mpg over Regular with Premium. So 173000mi./ 46.3mpg.for Regular=3736.5 gallons. 3736.5gal -3582gal= 154.5gal more Regular gas than Premium. So the cost difference would be $10459 for Premium - $9416 for Regular is $1034 total or $200 per year. For me it's Fun/Hobby so a few dollars extra is no big deal and I like the extra range too.