How To Increase Your Gas Mileage
 

ok so i just came back from a 1:30 drive and i came to a conclusion that the computer system is BS lol im just joking.

I took the car out on the freeway and i left it in 6th gear with cruise control on at 70 mph. i reset the computer by holding down the first button and i kept on driving. when the computer was done calculating i was getting about 36.6mpg and 69.5 mph. after few minutes it slowly started to go down to 33 and then to 30 and then to 29 and so on and on. after some time i started averaging about 24.5mpg and then 25 and then 26, 27, 28. so the highest that i had was 36.6 and the lowest that i had was about 24.5 on the freeway. It mostly depends on the road, if its bumpy and an incline the gas mileage gets less but if its smooth and a decline the gas mileage increases.

After an hour of driving on the freeway i decided to get off and drive on the street to see what happens. i got off the freeway and i started driving on the street. i wanted to reset the computer again so it starts off its calculation on the street. so i did it and when it came back on i was getting 33.6 mpg for like 5-10 minutes but then it went down to 28, 27, 25. the lowest i had on the street was about 22.3 but the average is anywhere from 24.5 to 25.2. i dont know if it will change tomorrow but after driving it for 30 minutes and going threw a good amount of red lights my average was 25mpg.

On the street when taking off on first i wouldn't let the rpm go higher then 1.5k. after 1st i would go to 2nd, after about 15-20 feet of driving on first. Right before i hit 15-20mph i would go to 3rd and go all the way to 25-30mph and i would skip 4th and go straight to 5th. and i was driving like that for most of the time. if i was approaching a red light i would go to neutral from 5th from far away and wait until it turned green and i would drop it to 4th and then 5th. I even tried 6th for few minutes but it didn't make any difference so i don't think we need to use 6th on the street.

so before i did this i was getting about 15.9 mpg now it says im getting 25mpg so give it a try and lets see what happens.

p.s. i probably would not be driving like this again because its so slow people might mistake me for a granny lol :ughdance:

Hmmm - bit of a paradox here - you've just improved your mpg readout by driving your car around the country, using fuel for no good reason!*

Don't worry mate - I've done it myself, plenty of times - any excuse to go for a drive!








*actually, there is a good reason - the reason is that it's just a damn fine car to ride in!

i actually love the drive lol i dont even have to be going fast in it. as long as im driving it :tup:

Another way to save gas while driving in the city, if your car has the sport package, turn off the Syncro Rev. This can save you quite a bit depending on traffic conditions and or/if you like to downshift while slowing.
Of course you cant heel & toe after turning off SR :tup:

So if you drive like you own a Nissan Versa, you get better gas mileage. I'm not sure how many 370z owners bought this car for its fuel economy...I bought it to enjoy all 332 ponies. If that means 15mpg, so be it. :driving:

I think you got the wrong car if you're worried about your gas mileage...

As for the Z's computer that calculates the gas mileage, are you talking about the left gauge or the nav computer that records trip mileage? If you're talking about the gauge, then it's not doing anything out of the ordinary. Those types of MPG gauges always fluctute between the low teens and 30s when cruising on the free way. If it's your trip computer though, then I'd have to say it's broken. That only calculates it based on how many miles you actually drive on each gallon, so it should never hit the 30s, unless you're finding a 30 mile decline somewhere.

i thought driving on cruise control was known to be well inefficient.... slowing u down on down hills etc so you need more gas to get up the next hill?

It is, because rather than coasting on downhills it's breaking to keep at speed and drops your RPMs. Cruise control isn't abut efficiency, it's about being lazy and not having to control your speed yourself on long trips.

Fuel efficiency may not have been the original purpose for creating cruise control, but it cannot be denied that using cruise control does indeed help gas mileage.

Edmunds did a test on this, and on average you can increase your mileage by 7%, but it can go up as much as 14%.

Other important notes from their testing, if you're going to idle more than a minute, turn the car off. This can save up to 19%.

Avoiding aggressive driving can save up to 31% (I know, I know, just sayin).

Driving lower speeds on long trips can save up to 14% (again, I know).

Things that didn't matter as much as they expected:
A/C On, Windows Up vs. A/C Off, Windows Down.
Tire pressure. (Which I'm pretty surprised to hear).

I have to agree with you!

One or two people buy 370z's then try to drive them as economically as possible. They are called Perverts.

One of my coworkers bought a solstice gxp (is that right?) and always drives under the speed limit. When queried about why he bought that particular car with no desire to actually drive that car, he said "I like how it looks.":icon14:

Well, some people buy cars for different reasons. I bought the 370 because I liked how it looked. Of course, I was looking for a car I was going to have fun driving, but the 370's looks is what made the decision final.

Don't drop it in neutral. Leave it in a high gear and lift off. If you lift off the gas fuel is cut, in neutral it's still idling along. Idle consumption isn't much but it could make a small difference over time.

Are you suggesting that leaving the car in gear while coasting yields greater fuel savings than placing the car in neutral?

When in motion, If idle RPM is @ 750, that should reduce fuel consumption as when the engine speed is @ 1K + RPM.

He is saying that when coasting (foot off accelerator), it is better to leave it in gear rather than idle.

The reason being at idle you're burning gas at 750rpm with cylinders firing.

Staying in gear, even though you're at say, 3000rpm, not one drop of fuel is used (or close to that). The ECU cuts the gas completely off.

Yep, what he said.

^ interesting you say that, because when I'm looking at my instant fuel gauge, and I drop it into neutral, I will go into the 40mpg+ area, but it stays in the 20s if I just let off.
Thoughts?

It goes 40+ in neutral but should go off the chart (60+) when you lift off completely.

I'll have to give this a better look tomorrow, sure would be handy to stay in gear.

Coasting in neutral consumes more fuel. In neutral, the injectors fire to keep the engine at idle, so you are burning fuel. Coasting in gear, the ECU switches to deceleration ... which happens to have an injector pulse width of zero.

True. But from my perspective, you can't always be driving it spiritedly, such as during heavy traffic.

So for those times when you can't be using all 332 ponies, why not drive to improve your fuel economy... you'll have saved fuel for those times you can push it!

let me just clear one thing out. i didnt get the z to drive like a granny, thats before breaking it in. as soon as i do im going to be flying

FYI: I'm no mechanic nor an auto engineer... just a dude using common sense and the fuel gauge read-out on my car...


I still don't understand why coasting in neutral would burn more fuel?

Are you suggesting that simply lifting OFF the gas consumes less fuel than placing the car in neutral to idle @ 750 RPM? I think there's a direct correlation between fuel consumption and RPM range - unless you're bogging the engine or loading it.

If your theory is correct, I could be driving down hill in second gear @ 6,000 RPM with my foot off the gas pedal (yet maintaining speed due to gravity & slope/grade) and save more fuel than popping it in neutral.

Very, very arguable, irrespective of however technical you may wanna get w/ injectors or widths.

Sure, there may be a point at which the speed one drives w/ the foot off the fuel pedal conserves fuel, but gearing and velocity have to be factored in and there comes a point where idling and maintaining a certain momentum (vs. losing momentum due to engine speed slowing the car) is more efficient.


Can you refute my non-technical assessment? If so, please do so in plain english.

Well, if he's right about the fuel getting cut during engine braking, then yes engine braking would save more gas than coasting. However, I find this hard to believe. Cut fuel = no more combustion. The drivetrain would simply be spinning the engine and sucking air through the pistons for compression braking, but without any ignitions happening (which means really they could cut the spark plug current off too). I suppose in theory this sounds possible, but I would think I would hear the difference between an engine that's undergoing combustion and one that isn't, and I would think the transition between the two states would be rather abrupt and noticeable. Sure seems pretty smooth to me.

I'm not saying it isn't true, I'm just saying I find it hard to believe :)

I've read here a few times that coasting in gear, gets you better mpg than dropping to neutral. Although this was a rather weird idea at first, I actually believe it. I have paid attn to that constantly moving horizontal bar graph in the Z's computer readout. It is true, when lifting off the gas and coasting in a gear, at higher speeds, the bar graph reads completely full (i.e. 60mpg or however high it goes up to); this is not true for when you drop into neutral, it shows like 40s or something.

That alone convinces me that you're better off coasting in gear.

Finally, I drive highway a lot, long trips for work. I've done this a few times, setting the cruise to 75mph. On one 200 mile trip, I averaged 27.7 mpg; on a second, slightly shorter trip, I averaged 28.5 mpg.

The mechanical noise of all the engine parts moving far exceeds any noise the actual ignition makes.

In full lift off the injectors do not fire (there may be no spark either, but I'm not sure). It matters not the gear or the RPM's as long as the engine is above idle speed. As you approach idle the injectors will begin firing again to prevent stall.

You do get great mileage in neutral as well because idle fuel burn is minimal and there are times where that is going to save more fuel than lift off if you can do it for longer. But if you're going down hill you absolutely should be in gear.

Theory and engine mechanics are one thing... real-life dynamics and physics are another. With an engine stationed @ a laboratory, I can see that an engine will conserve fuel by being in gear, however, not on our highways...

What I'm getting at is that the gear you're in makes a difference! To elaborate, lets assume we're coasting down a hill. Without using the gas pedal whatsoever, first gear will be less efficient to coast in than 2nd gear, than 3rd, gear, etc.... this is due to the ability to gain greater speeds. Even coasting in 6th gear will eventually reach the point where the car will NOT gain more speed. Popping the car in neutral in this case SHOULD result in increased speed (since the engine RPM's don't hold the car at a steady speed) and this should result in more distance covered in less time (speed). This is inherently what fuel mileage equations take into account...

So as I see it, when variables of physics are thrown into the equation, the whole concept of fuel savings needs to be reevaluated.

Someone should try this and report to us the finding:

1. Find a stretch of road (at least a mile) w/ a slight grade.
2. Warm-up car and go to the top of this "hill".
3. Reset fuel mileage gauge and immediately perform step 4.
4. Accelearte from first gear to 25 MPH at a steady rate.
5. Place car in 3rd gear and coast to bottom of "hill".
6. Record mileage info.
7. Perform steps 1 through 4.
8. Place car in 4th gear and coast to bottom of "hill".
9. Record mileage info.
10. Perform steps 1 through 4.
11. Place car in 5th gear and coast to bottom of "hill".
12. Record mileage info.
13. Perform steps 1 through 4.
14. Place car in 6th gear and coast to bottom of "hill".
15. Record mileage info.
16. Perform steps 1 through 4.
17. PLACE CAR IN NEUTRAL AND COAST TO BOTTOM OF HILL.
18. Record mileage info.


While this is not entirely scientific, it should produce consistent results. Ideally, we want to maintain consistent tire, engine oil and road temps. Same goes for the weight in the car (passengers, luggage, etc)... and if you test w/ the windows up or down, do so in every instance of this test.

If I were a betting man, I'd say Neutral will generally yield better mileage, especially as slope (and speed potential) increases! :)

Yes, the compression of the engine will slow you down, and the gear you are in will determine how much it will slow you down. You will have used the same amount of fuel getting to the bottom no matter what the gear (zero as long as the hill is steep enough) but your speed at the bottom will obviously be very different depending on how much engine braking there was. You will go further and faster in neutral which means you could potentially save more fuel that way in certain circumstances as you will have more inertia and hence wont need to re-accelerate up the next hill as much.

There is a distinct change in pitch between accelerating and coasting.

Agreed. I just find it hard to believe that what my ears are hearing during engine braking is just restricted airflow pumping through the cylinders with no combustion.

It can get mind bogging, and complicated to explain and understand.

Back in the early 80's (before FI was common) they sold mod kits that did this. There was an inline fuel switch, an RPM sensor and a throttle switch. When you lifted off fuel was cut to your carburetor provided you were above the preset stall speed. It's standard practice on modern cars with fuel-injection and manual transmissions.

Automatics don't always implement this as the transmission must be in full lockup mode for it to work.