The key to high MPGs

[5pyd3r]

Hi everyone,

Many of you know this already. This is for the ones not getting the mpg they're trying to get and don't know why.

The mileage thread seems to have incredibly inconsistent numbers and some people saying 'I drive like a grandma' or 'I always drive under 2000 rpms' and they're surprised that they are getting ridiculously low MPG numbers.

First of all, when you fill up, if you're looking to measure MPG, just do it click to click. It is so much easier and more acurate:

Fill up tank once till the pump clicks off. Drive x number of miles. Fill up again till the pump clicks off. Use the second fill up # of gallons to divide x by.

Now, on to the actual driving. These engines suck with mileage in both high RPMs as well as low ones. You need to shift at ATLEAST 2500 RPMs. ATs can do this just as well as MTs. In fact, ATs can pull off higher numbers in highway driving. Something unheard of until recent changes in transmission design tech.

I average 37mpg with the AC on most of the time and highway/city about 70/30. I've hit 40mpg between Dallas and Austin several times.

This is on an LX AT Sedan. I change gears at 3500 so I don't really compromise on picking up speed. It's just gradual increases. I do however use the highest gear possible at all times. Just remember that if you're doing anything below 2000 rpms, YOU NEED TO BE IN A LOWER GEAR.

Stay around 2500 at all times and change gears to adjust when your speed changes. Watch those numbers do thru the roof!

The following is something I pulled from ecodrive.org The data is a little old and applies very generally so their numbers may be a little different. The rest of it has interesting tidbits here and there.

www.ecodrive.org > HomeThe golden rules of ecodriving
In the last decades, engine technology and performance of passenger cars, lorries and buses have improved rapidly, however, most drivers have not adapted their driving style. Ecodriving is adapted to modern engine technologies and means smooth and safe driving at lower engine revolutions. Ecodriving is easy to learn and it has been shown that written information itself has a substantial impact on driving behaviour, on safety and on fuel consumption without increasing travel time.

There are five basic rules to follow.

* Shift up as soon as possible
* Maintain a steady speed
* High gear and low engine RPM
* Anticipate traffice flow
* Decelerate smoothly



Shift to a higher gear
Shift up between 2.000 and 2.500 revolutions. For both petrol and diesel fueled cars.

Part of the power of a passenger car's engine is lost by internal friction. These losses increase with engine speed. By driving at low engine speeds these losses remain limited, which reduces fuel consumption. The efficiency of a car engine also increases when a high engine load is used (giving more gas at low engine RPM (revolutions per minute)). Under these conditions the engine power is generated more efficiently. During acceleration the most efficient way of driving is therefore to shift up as soon as possible (at low engine speed) and to apply a relatively high load on the engine. Driving in a high gear automatically requires a high engine load to keep up with traffic.

In order to use the efficiency of a car engine in an optimal way, a maximum engine speed of 2500 RPM for shifting is recommended for petrol/LPG engines. Because diesel engines generally reach their optimal efficiency at lower engine speeds, a maximum engine speed of 2000 RPM for shifting is recommended. A rev(olution) counter is a useful aid to determine the right shifting moment. The shifting recommendation is anyhow applicable to cars with a manual gearbox, but it can also partly be applied by cars with an automatic transmission (see 'cars with an automatic gearbox). The recommended way of shifting is in no way harmful to a properly maintained engine.



Maintain a steady speed
Maintain a steady speed, using the highest gear possible!

When accelerating, energy in the fuel is used to propel the car. Part of this energy is wasted when you brake. You may experience this phenomenon after hard braking; the brakes have become very hot because of the transformation of propulsion energy into heat. Therefore, repeated acceleration and braking requires a lot of energy (fuel).

This can also be explained by the fact that the average car only needs 5 kW of power to drive at a steady speed of 50 km/h (at 120 km/h the amount of power needed increases to approximately 25 kW). The remaining 90% (or more) of the engine's power is only needed for acceleration or for driving at very high speeds. By driving steadily as much as possible, the wastage of energy and fuel remains limited. Try to avoid unnecessary acceleration and braking. Cruise control is a useful aid for smooth and steady driving.

Driving at steady speed not only increases fuel-economy, but it also has a positive effect on exhaust emissions, traffic safety, traffic flow and passenger comfort.

High gear and low engine RPM
As already mentioned, the power needed to drive at a steady speed is rather low. Therefore, a high gear can be engaged without any problem at low engine speeds. This saves fuel and is in no way harmful to the engine, when it is properly maintained

The opinion that the accelerator pedal is directly fixed to the fuel consumption is incorrect for a petrol engine. The accelerator pedal operates only the throttle/ butterfly valve and consequently definitely only the air quantity. On the basis of this position and also other influences such as the momentary revolutions, the fuel quantity used is calculated by the engine. Each small reduction in the level of revolutions means that less fuel is needed.

Anticipate traffic flow
Look ahead as far as possible and anticipate to surrounding traffic!

In order to drive at a steady speed (as discussed in recommendation 2), it is important to anticipate to surrounding traffic to avoid unnecessary braking and accelerating. For example, when approaching traffic lights, when overtaking traffic like cyclists or agricultural vehicles or when driving on a busy highway, anticipating to other traffic can have a big influence on how steadily you drive.

Many situations can already be noticed far ahead, long before approaching the situation itself. In case you use cruise control (see recommendation 2) you will have to anticipate even more to be able to make full use of its benefits.



Decelerate smoothly
When you have to slow down or to stop, decelerate smoothly by releasing the accelerator in time, leaving the car in gear!

Petrol and diesel cars manufactured from 1990 onwards, are generally equipped with fuel injection combined with an electronic function that cuts off the engine's fuel supply under engine braking (accelerator released and a gear engaged). The advantages of this fuel cut off function can be used by releasing the accelerator in time, for example when approaching traffic lights. This also reduces wear and tear on the brakes, reducing maintenance costs. Engine braking, not only has a positive effect on fuel consumption, but also on exhaust emissions, traffic safety, traffic flow and passenger comfort.

In case of less modern cars with a carburettor and older diesel cars (generally manufactured before 1990), it makes no difference whether you decelerate with gears engaged or disengaged, for the carburettor is a mechanical device that is not equipped with electronics to cut off fuel supply. These cars consume an equal amount of fuel under engine braking and when idling. However, releasing the accelerator in time still avoids hard braking and improves the durability of the brakes.

[e60.deluxe]

good write up. the main 2 things are going to be how gently you accelerate, and how often you dont have to slow down. shifting at X RPM doesnt do a whole lot.

Petrol and diesel cars manufactured from 1990 onwards, are generally equipped with fuel injection combined with an electronic function that cuts off the engine's fuel supply under engine braking (accelerator released and a gear engaged). The advantages of this fuel cut off function can be used by releasing the accelerator in time, for example when approaching traffic lights. This also reduces wear and tear on the brakes, reducing maintenance costs. Engine braking, not only has a positive effect on fuel consumption, but also on exhaust emissions, traffic safety, traffic flow and passenger comfort.

exactly. ive been telling people this alot here, but not many people seem to believe me. finally something thats worded better.

[an0malous]

thank you for the statement about fuel cutoff.
we recently had a big debate on our forum about this.
where people were swearing black and blue that its smart to coast in neutral


god help the idiots.

[sf-si-02]

My mpg is purely a function of how far down the pedal is depressed.... on my si, my previous ep3, all of my e30's I suspect it is the same for the non-si 8th's

[e60.deluxe]

Originally Posted by sf-si-02

My mpg is purely a function of how far down the pedal is depressed.... on my si, my previous ep3, all of my e30's I suspect it is the same for the non-si 8th's

not quite. WOT @ 40mph in 6th doesnt use as much gas as WOT in 2nd.

[5pyd3r]

Originally Posted by e60.deluxe

good write up. the main 2 things are going to be how gently you accelerate, and how often you dont have to slow down. shifting at X RPM doesnt do a whole lot.

How gently you accelerate is huge. I should have stressed on that more.

Shifting at right rpms is just something you should combine gentle acceleration with. If you gently accelerate but stay under 2000 the whole time, your numbers will suck.

Grandmas get just as bad mpg as vtecheads.

[5pyd3r]

Originally Posted by an0malous

god help the idiots.

He refuses to.

[5pyd3r]

Originally Posted by an0malous

thank you for the statement about fuel cutoff.
we recently had a big debate on our forum about this.
where people were swearing black and blue that its smart to coast in neutral

My dad taught me engine braking. This is on an 800cc carbuerator engine 4 door MT!

It wasn't so much about fuel efficiency than it was about 'slow down correctly' for him. He would have me shift to a lower gear and de-clutch to slow down.

Ever seen a car get rear-ended in neutral?

[civsnake]

Originally Posted by e60.deluxe

not quite. WOT @ 40mph in 6th doesnt use as much gas as WOT in 2nd.

I think he's referring to steady speeds, not accel. Full throttle in either of those gears will result in acceleration. I would not recommend, however, driving at 40mph in sixth gear. At that point you're bogging the engine and it will be running rather inefficiently. Cruising at 40 in fifth isn't so bad.

My Si recipe for high mpg:
If I'm accelerating, I shift at 3k. If I'm cruising I try to keep it between 2k and 2.5k. Of course on freeways in sixth you'd be going rather slow at these rpms. 68mph happens roughly at 3k rpms. If I can stay there I can get pretty good mileage out of my car. A typical tank for me driving in this manner will yield about 31-32 mpg, being 85-90% freeway driving. This of course also takes into account previously stated ideas about anticipating traffic and stops and avoiding unnecessary changes in speed.

I should say that even if I do my commute more aggressively (85mph, hitting 6k+ rpms sometimes, accelerating quickly) I can still get 28 mpg out of it. This is just to give people a better idea of the route I take.

[sf-si-02]

Originally Posted by e60.deluxe

not quite. WOT @ 40mph in 6th doesnt use as much gas as WOT in 2nd.

I should have added the following disclaimer: "As long as you are not driving like a retard."

But I do agree with you

[inyong1988]

does this really help? how many miles can you get with a full tank of gas?

[5pyd3r]

Originally Posted by inyong1988

does this really help? how many miles can you get with a full tank of gas?

A full tank of gas seems to mean different things to different people.

I fill up till the pump clicks off and fill up again right around when the light comes on. I get around 375.

Now if you give it another 2 gallons after the pump clicks off and drive it till all the bars go out on the gauge, you'll be off by 4 gallons and start thinking your car is a hybrid.

[inyong1988]

Originally Posted by 5pyd3r

A full tank of gas seems to mean different things to different people.

I fill up till the pump clicks off and fill up again right around when the light comes on. I get around 375.

Now if you give it another 2 gallons after the pump clicks off and drive it till all the bars go out on the gauge, you'll be off by 4 gallons and start thinking your car is a hybrid.

Is your SI? or lx/dx/ex?

[5pyd3r]

Originally Posted by inyong1988

Is your SI? or lx/dx/ex?

LX AT Sedan

[an0malous]

Originally Posted by 5pyd3r

My dad taught me engine braking. This is on an 800cc carbuerator engine 4 door MT!

It wasn't so much about fuel efficiency than it was about 'slow down correctly' for him. He would have me shift to a lower gear and de-clutch to slow down.

Ever seen a car get rear-ended in neutral?

I distinctly remember saying the exact same thing during the argument lol.

but they wouldnt believe us.
they also didnt believe us when we told them neutral coasting is illegal, as well as stupid.

you wouldnt believe how many people do it. and actually think its smart.

[Jardiniboy]

This is another way of getting high MPG

Si Owners - Stay out of vtec
DX/LX/EX Owners- Stay in vtec,

[NitrousG35]

Originally Posted by Jardiniboy

This is another way of getting high MPG

Si Owners - Stay out of vtec
DX/LX/EX Owners- Stay in vtec,

Too funny.

[Jardiniboy]

Originally Posted by NitrousG35

Too funny.

It's funny but true. Haha

[20strong]

Is there anything bad about filling it till it gets to the top of the nozzle?

[inyong1988]

Originally Posted by 20strong

Is there anything bad about filling it till it gets to the top of the nozzle?

nope