I was wondering what is the most efficient way to drive the G? Because normaly I would just shift to the 5th gear as soon as possible with my AT G in MM. Does that waste more gas? or it really doesnt do anything? As soon as i m in the 5th gear i dont go any faster.

 

if you wanna save gas then dont drive it

 

well, that is really not the point. I am asking if i were to cruise around 60-70km, would it more fuel efficient than compared when i drive in the 3rd or the 4th gear? I need to know because I was debating with my friend about this.

 

I used to drive 160 miles a day roundtrip commute to my old job 5 days a week. It was all interstate. I found I got better gas mileage by NOT using the cruise control. Instead I would keep constant pressure on the gas pedal, which probably drives folks crazy as you'll be going slow up inclines and fast down hills. But it works.

 

For the most part, being in a higher gear yields better economy only because it limits how fast you can accelerate. If you accelerate the same (same acceleration G-force) in either 3rd or 4th gear, the fuel economy is basically identical. There is a slightly increased fuel usage at very high revs due to the ECU running a bit richer and increase friction loss from the high revs, but it is not nearly as substantial as you think.

Short version -- it doesn't make any difference when cruising or accelerating gently.

 

THANK YOU!! THATS WHAT I WAS LOOKING FOR!

So, as an example, it wouldnt be more efficient if i were i drive at 60km in the 5th gear because the engine is going at lower RPM compared to the 3rd and 4th gear?

 

dont use MM. auto will yield better efficiency - if you dont floor it all over the place

 

Already! thanks!

 

I will not sacrafice a single rev over gasoline.

I love driving my 6mt to its limit.

 

Yeah absolutely not. It would be the same. What uses fuel is doing work, such as accelerating or maintaining speed on an incline. Until you get to extreme cases like 6,000rpms... and even then it's not a huge difference.

WORK uses fuel. Floor it in 5th, floor it in 3rd, if you stop accelerating at the same speed, you've used the same fuel, just in 3rd you used more fuel for less time and in 5th you used a little less fuel for more time. You still did the same amount of work -- accelerating from one speed to the other. Any deviation from this is fractional and hard to measure.

Being in a higher gear helps you get better economy by LIMITING your acceleration potential. You simply cannot take off like a bat out of hell if you are going 50mph in 5th gear ... the torque of the engine cannot do it. So, you get better mileage by driving around at low RPMs... but not because it's low RPMs --- just because you are unable to accelerate aggressively.

If you have nav you can witness this yourself by turning on the fuel economy screen and watch the real-time mpg monitor. I've done this test and showed others in my 6mt... people have a hard time believing this until they see it.

 

haha, oh man, now i get it! thanks dawg!

 

Its like riding a bike IMO, only you're the engine. You have to shift to do less work and go faster. Anyways, well said mal_tx!

 

this is funny because me and my friend has the EXACT same conversation the other day. I spoke to a mechanic at my job and asked him this question and he said there is 100% a difference and dont pay attention to what that stupid nav says. To me i would believe its common sense as well. If your doing 60mph in 6th gear at 2k rpm or 60 mph in 3rd gear at 4700rpm, how the hell could the engine not be getting better mileagle. Guy said you do 100% becasue the engine is doing less work meaning the cylindars are firing less agreesivly and taking in less air, which means less fuel.

its common sense that the way people burn the most gas is by accelerating quickly....accelerating quickly means always having your enige in high rpm.

 

Except that's wrong. That used to be the case with engines back in the 70s maybe but with today's fuel injected computer controlled engines, it is not true. The nav is measuring the fuel consumption ... it's not going to be wrong, sorry. You should think about the engine "doing work" in terms of how much torque it is producing above what the car coasting will produce if you lift off the gas. That's all it needs to do ... make the same or more power than the car is making at it's current speed. Think also about the case of going down a gentle slope.. you get ridiculous high mileage that way, because the engine doesn't have to do anything... if the slope is too great, heck, the engine will actually hold your back from accelerating.

60mph in 6th gear at 2k rpm vs. 60mph in 3rd at 4700rpm uses the same fuel and the same air. It simply does not take much fuel to maintain 60mph, regardless of gear (ok maybe not 2nd gear). Press the gas pedal and now you will start to use more fuel. Floor it, and the engine will receive the max fuel/air it can burn, determined by the ECU given data fed to it by lots of sensors. In 6th gear, that is probably going to be a smaller amount than in 4th, in this scenario, but then 4th will send you accelerating aggressively ahead while 6th will just barely speed up.

Here's another piece of info related to this ... if the engine is over 1500rpm and your foot is off the accelerator, the engine is not given ANY fuel to burn. The car is turning the engine instead. Think about this for a minute and it will help to understand what I wrote above... at 60mph in 3rd, you only use the amount of fuel necessary to keep you from SLOWING DOWN. Same goes for 60mph in 6th. And, given the same road grade (uphill/downhill) and the same conditions, and not talking about extreme cases like near redline, it's the same amount of work needed to maintain a speed.

There's no place else for the stored energy (in the fuel) to go... except waste, in the form of heat and unburned fuel coming out the tail pipes. Today's engines are pretty efficient at getting the maximum amount of produced energy from their fuel.

On older engines you could flood the engine by flooring the gas at 60mph in 6th gear... thereby "wasting fuel." Not anymore.

And don't call me 'dawg' please

 

Have a vacuum guage installed and practice keeping the vaccum as high as you possibly can; this will get you the best mileage and help your overall economy driving habits...