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hello everyone,

most websites and authorities agree that 55mph is best balance between speed, aerodynamics, and fuel efficiency. i've also read it can be even more fuel efficient to drive at the lowest speed/rev of a high gear.

for example, i drive an automatic 2006 wrx (turbo). the manual says 65mph is max speed of gear 2. so, i was theorizing, am i better of mpg wise to drive 55mph (2nd gear)... or is it better to drive 66mph (lowest speed/rev) in 3rd gear?

thank you,

kenneth

You definately don't want to drive 55 in 2nd gear. Drive 55 in 3rd gear and see what that does. You will be happy.

Hi Ken:

___Throw everything you have read, thought about or even considered out the window and let us start all over.

___The best FE will usually come about in top gear at the lowest speed that gear can be maintained. 2nd at 55 or 3rd at 66 is way off the mark assuming you have a 5-speed MT. Get her in 5th and hold anything above 40. The numbers achieved will astound you if you are OEM FCD or SG-II equipped ;)

___Good Luck

___Wayne

thank you,

but i drive an automatic. how does that affect things?

jianye3

Hi Ken:

___You want to fake shift or at least let the Torque Converter lock up. I am not to familiar with the WRX but I would have to assume it would be modeled similarly to every other AT’s with a 48 mph or so top gear lock. Once locked, enjoy the show and the fuel savings ;)

___Good Luck

___Wayne

i have a four speed auto, fourth gear comes in at 40mph, howevr, it stays at 1500 rpm from 40mph -45mph. at about 50 mph it is at about 1750, which is where i have the best FE. so, its going to be a few mph above the lowest point in your highest gear, so as wayne says, 48mph should be your spot for fifth, maybe even earlier, but 50mph may be your magic number. sgii tunes this for you, or you could do tests with different tanks at different speeds for highway.

Hmm I got my 2003 manual open. I guess they changed the gearing from 2003 to 2006, cause in 2003 the top speeds are:
1st 38mph
2nd 71mph
3rd 112mph

Anyways, I like the fuel economy hints listed in chapter 8. The first one, "Select the proper gear position for the speed and road conditions".

But yeah, you want to be in the highest gear possible to keep the car moving. Though with automatics you don't have much choice about that. I used to have a friend that insisted in his Ranger that it was better to run it in Drive instead of Overdrive. He just didn't understand.