[Wilkie]

My morning commute is about 25 miles of mixed city/highway. The speed limit for most of the city portion is usually around 40mph.

I own a 6-speed manual and I was wondering about my gas mileage in 4th gear versus 6th at 40mph.

It seems as though I can be in 4th gear with higher rpm's but the engine doesn't seem to be working hard. Or.......

I can be in 6th gear with lower rpm's but it seems as though I have to press harder on the gas to maintain speed.

I was wondering if any of the scangauge users could provide some input on their observations.

I don't know-maybe I'm just being stupid but I just spent $70 bucks filling the FJ up and I've been trying to think of ways to save a little. I already drive like grandpa on the highway.

Wilkie

 

[DominicG]

At any speed, the Lower RPM the better.

I have an AT but i notice my mileage is always better under 2k rpm. Around town that is hard to do, especially in traffic. But on the highway thats easy. With all my mods, 68mph at 1875RPM is the cutoff for my chance at decent mileage.


If you can keep it under 2k rpm, then you will without a doubt see respectable mileage.

 

[Wilkie]

At any speed, the Lower RPM the better.

Thanks DominicG.

I was trying to figure out if mpg was solely a function of rpm's, or throttle position, or both.


Wilk

 

[DEWFPO]

It's both. But studies have shown that it's better to be at a lower rpm and wider throttle position for better mpg (but only to a point). With a MT you don't want to lug a gas engine (any engine) below about 1,100 rpm. Diesels can handle lugging better at lower rpms because of the extra torque they make at low rpms.

DEWFPO

 

[DEWFPO]

I forgot to mention, the reason for getting better mpg with the lower rpm/high throttle opening scenario is because of lower pumping loses due to the throttle plate causing less of a restriction at higher throttle positions. At low rpms, your cylinders can fill up easier this way and your volumetric efficiency is slightly improved under this scenario.

DEWFPO

 

[JData]

Pulse width/fuel delivery is smaller at lower RPM regardless of throttle angle.

 

[Woodsman]

I have an automatic but I am guessing that, at 40 mph, you're sweet spot may fall in 5th gear. Efficient yet not so slow as to cause lugging.

 

[FullTimeStud]

I would use 6th gear at 40mph for the best fuel mileage.

 

[FJ FunJunkie]

I have an automatic but I am guessing that, at 40 mph, you're sweet spot may fall in 5th gear. Efficient yet not so slow as to cause lugging.

don't you mean the woodsman has an automatic but I am guessing that, at 40 mph, you're sweet spot may fall in 5th gear. Efficient yet not so slow as to cause lugging? or do you not refer to yourself like that anymore? heheheh
jus messin wit ya woodsman.

my sg shows that my best mpg is in 4th around 40 mph.