Was the dyno run done in 5th gear(1:1)?
Also running less than 93 octane(or whatever is the highest available) is not a great way to save money.
Agreed, if they ran your car in 4th gear, which is what would have been used on practically any 5-speed Mustang prior to 2011, then you will have lower numbers. My dyno guy did this for my 1st run, and my next question was, what gear did you just use. When he said 4th and I to explain that 5th gear was the new 1:1 gear, and to run it again. We saw a bump of about 12hp and 40tq by using 5th.
As for the gas, I've explained this over and over and over on threads. It is pointless to put lower octane gas in your car unless higher octane fuel simply isn't available at the gas station your at, and another gas station simply isn't an option at the time.
The cost difference between mid-grade to premium is about $0.15, and regardless if fuel sells for $1.50 or $6.00 per gallon, the cost differential is almost always constant $0.15 per gallon.
15-gal of 89-Oct @ $3.50 = $52.50
15-gal of 93-Oct @ $3.65 = $54.75
Savings = $2.25 for fill-up of 15-gallons.
If you drive 20,000 miles per year and you average 20mpg, that save you a whopping $12.50 per month, or $150.00 per year.
I hope this sheds light on how absolutely ridiculous and fruitless filling up with less than premium octane full really is.
Now, if you seriously need to scrape to come up with an extra $12.50 per month for premium octane fuel, than you have much bigger financial problems that you're willing to admit to, on top of the fact that you bought the wrong car as well, as a Mustang GT will cost more to own per year over a V6 model simply based on the oil changes, as the GT 5.0 takes 8-quarts of oil instead of 5-quarts, and that alone will cost you about an extra $15 per oil change.
