I do drove to Oklahoma last weekend and hit some pretty big hills. I have a 6 speed 3.21 gears with 32" tires. Most of the trip I had to stay in 5th with occasional use of 6th. If I regear to 4.56 I know I will be able to use 6th more. My question is with 3.21 I averaged 14 mpg on the highway at 70-75 mph. Would the ability of the 4.56 gears improve my highway gas mileage or have no affect or still be bad mpg?

 

No ideas anyone?

 

Your best mpg will be with 3.23s at 60-65 mph in 6th gear. That should put you turning around 2k RPMs

Going to a bigger gear like that will make your engine turn more RPMs, and lower your MPG

 

You might want to just get you computer updated to your new tire size.
Since they are not over 32", Your dealer can do it for you.

If you regear, you will also have to make a similar update so that your computer will know how to take the new ratios into account.

 

Its a sport S, so it should be calibrated for 32s from the factory, right?

 

It's 29"s, I know at 3.21s my optimal mph is really around 55 with a manual. But I make occasional long trips and those slower speeds are not an option for me.
I'm really just curious if 4.56 would do better mpg at 75 mph than 3.21 at the same speed. But keep in mind most of it I do with 3.21 at 75 mph is in 5th gear turning 3k. So I know regearing to 4.56 will let me stay in 6th.

 

I guess the question is....do you plan on staying with 32's? If so then 4.56 will probably be more gear than you want.

 

No upto 35s

 

If it came with 29s then you cant trust the speedo or digital MPG gauge anymore until you get it recalibrated.

 

I'm doing the math in my head and I'm not worried about the speed. I just want to know if 4.56 will get better mpg in theory in 6th gear than 3.21 in mostly 5th cause hills I'm driving through can take 6th gear. I'm not worried about what the speedo is saying as i am worried about how the engine is performing.