You will get a feel for what's too slow of a speed in 6th. If it's flat 40 shouldn't be an issue and if you have hills you may have to pick up the pace or grab 5th. You can use the economy gauge and bounce 5th against 6th. It's not perfect but as with most Fords I've driven the closer you get to 2k on the RPM the thirstier they get except for my old Focus.

 

To answer this:

The top gear in every Mustang since 1983/84 (when Ford started using a 5-speed) has been designed as an over-drive gear for gas mileage, and since that time (with the exception of some Cobra and GT500 models) the top gear ratio has always been in the .62 to .68 range, which means top gear in the MT82 equipped 6-speeds is not much different at all in terms of overall gearing compared to the older 5-speed model Mustangs. The difference between the current 5.0 engine and the older 4.6L and 5.0 CIB Mustangs would be the torque curve from the motors, which all were pretty well tuned for Torque delivery over pure HP.

Compared to most German or Asian built cars built up through to 2011/12 (when everyone has started to gear 7/8/9 speed transmissions with a range of overdrive gears), those have been typically geared with every to have good equal spacing for the car to achieve acceleration up to the top speed of the car, most usually selecting the top gear in their cars to reach near redline at the top speed of the car. This obviously does not apply to our Mustang, as 6th gear would be capable of over 250 mph with stock 3.31 gears, or 225mph with 3.73 gears at engine redline.

When it comes to Mustangs, this is not a GT phenom, Ford does it to the V6, Boss, and GT500 as well, plus Chevy does it to the Corvette and Camaro as well. When you change the rear gears to a lower ratio like 3.55, 3.73, 4.10, etc..., you will minimize the overdrive gearing effectiveness, allowing 6th gear to drive along with less engine bogging. If you like to shift, and don't drive a the majority of time on the highway, then 3.55 or lower gears will be for you.

 

^^ i want a 10 speed like my old Schwinn

 

I have 3.73 gear and i hardly use 6th gear. 5th gear at 3000rpm is like 70mph. 6th is so boring, like a dead fish. My mpg is only 15 since i stop using 6th. This is my weekend car so i don't give a **** about mpg. I usually start in 2nd gear as well. I shift at 3k-4k normally. This make it so much fun to drive. I understand people shifting at 2k or even less for better mpg, luckily i have a 2nd car for that.

 

i hear you. this is my daily driver and i'm usually not in a hurry to get anywhere when going to work ha! so 2k shifts are where i'm at. i just got done with first longer distance trip. 238 mile round trip (now close to 1700miles on the car). 10 gallons, 23.8mpg at ~2100rpm doing 72ish mph. now that does include about 10 miles city driving 25-30mph. 3.55 gears.

anyway you look at it this car is very satisfying. i might be more satisfied with dark grey or black wheels though! time to hit the sterling grey threads for ideas.

 

For me I'm still getting use to 5th gear as a 1:1 vs my gt500 that 4th is 1:1. To be honest I like the gt500 tranny an gear set better than the 2013 5.0 tranny an gear set.