ARTICLE: How to get the maximum Fuel Efficiency

[Sagittarian]

Frankly, these days I use only normal petrol in my Aveo. It gives me around 13.7-14.0 kpl and when I use the premium variety, it may go up or down, depending on from where I filled. Moreover, the additives in the premium variety may not allow a proper run-in in new cars (I am told). Anyone can throw some technical light on this?

[vivekiny2k]

Originally Posted by Sagittarian

I remember a news item published some time ago in a news paper. There was a bit of an interview in it with a truck driver transporting fuel. The interviewer asked him whether he was carrying normal fuel or premium. You know what he answered? It depends on the tank into which it is emptied at the retail outlet!
So much about premium. I guess the only thing that one can be sure is the price - it is premium.

well, I'd say someboy interviewing a truck driver is stupid enough to get that kind of response. Why or how does the driver care about what he is carrying, as long as he knows it's inflammable fuel.

[rahuldeodhar]

The answer to both question is depends -

1) Blower speed does not make AC switch on/off on its own.
2) AC load reduces as the cabin cools hence
3) Setting thermostat to higher temps (hotter) reduces AC loads


to increase effectiveness of AC (at best efficiency possible) you can look at following steps:
1) retaining cabin air (not allowing outside air) lets you cool the cabin faster (if you have many people in the car you should let fresh air inside - this is set using the specified knob -
2) if cabin is too hot (parked in sun etc) - you might want to set blower to full open windows for a little while and let outside air in the cabin (using the air supply controls) then when temp has stabilised you can up the windows, set blower to normal and switch on the AC - if you do this while in shade it happens faster -
3) if cabin temp is similar to ambient temp (at night / underground parking) - then you can simply keep the blower to normal setting and start the AC
4) typically there is no specific "normal" setting - it depends on outside temp - the hotter it is outside the higher the "normal" blower setting

Rahul

Originally Posted by joseph5600

I had a question regarding use of Air conditioner and achieving max kmpl.

1. Is the use of blower speed related to the working of the AC? ie. Suppose if we set the blower speed to the lowest, will it make the AC switch off automatically after the cabin gets cooled?
2. Is the same applicable with the thermostat? So if we set the thermostat to a medium temperature range, will it help in the switching off engine after the cabin temperature reaches the temperature set?

[Xehaust]

Just wanted to share this with everyone.Calculated today.

My Astra is giving 10 kmpl (AC Usage - 35% or more ON) !!!
(Method Used to evaluate - Fill tank to the brim, set ODO on Zero and check at next fill - 400kms/40 litres)

40 & not 50 (The Astra capacity) because the 10 reserve are still there when i refuelled today and were present when i filled the tank previously. I dont want my car to get all that gunk at the bottom of the tank into the engine now do I

It was always between 5-7 first with less AC use (With the OE tyres - 185/70 R14)

I was shocked beyond belief as i am now on thick tyres - 205/55 R15 & more AC use.
Plus, my driving is 70% cold starts due to short distances.

I achieved these figures by following the tips on the first page.
And this tank full did include one such drive where i revved till the red line & believe me, generally, the needle goes right down then and there.

Finally, this is IN-CITY with traffic at varied timings and absolutely no highway use.

This was achieved with the tips on the 1st page including:
- Changing gears at about 2000 RPM
- Cruising speed of between 60-80 kmph
- Minimal Clutch Usage
- Minimal braking by anticipating ahead traffic and leaving the accelerator.

Also worth mentioning is that driving has become more relaxing due to this. Of course, the once in a while sporty driving is present. The car is completely stock save for the tyres & rims. Petrol used is "Saada" Petrol and no additives.

[cyneverdie]

23 rd jan , hmmm . The cold weather always gives me MORE power and i presume much greater FE if i followed what your doing.
Truly believe the cold makes a big difference and man it was cold.

[vasudeva]

This is from IEA/OECD/ECMT 2005 report on Making Cars more fuel efficient, which considered methods to obtain better FE. This is synthesis of research and not some opinions:

For diesel vehicles, methods to discourage high speed driving and discourage shifting gears at high RPM appear to lead to higher FE.

For modern gasoline engines, too high RPM levels in too low gears result in lower FE.

If aggressive driving involves `revving' the engine to a high RPM before gearshift, the impact on fuel economy is greater in diesel vehicles due to the higher internal engine friction in a diesel engine.

Results from studies chave suggested fuel economy gains of 5 to 20% are possible from driver training. In the last decades, the engine technology and performance of both passenger cars and trucks has improved rapidly, while most drivers have not adapted their driving style. Their driving is thus not suited to modern engine technology characterised by high power, high torque at low RPM, electronic engine management, turbo chargers and variable valve technology.

ECO-DRIVING as defined in European countries is an adapted driving style, which best fits modern engine technology. ECO-DRIVING means smart, smooth and safe driving at lower engine speeds (1200–2500 RPM), which saves 10% fuel on average. Finally there is the ECO-DRIVING Style Recommendations (from NOVEM) which are as follows:

Shift up as soon as possible. For petrol/LPG cars at a maximum of 2500 RPM, for diesel cars at a maximum of 2000 RPM.
Maintain a steady speed, using the highest gear possible.
Look ahead as far as possible and anticipate movement of surrounding traffic.
When slowing down or stopping, decelerate smoothly by releasing the accelerator well
ahead of time and coasting, leaving the car in gear.

Source: Interpretation of Driving Style Tips, TNO Automotive, report for NOVEM, 2002.

European governments have conducted several programs to support ECO-DRIVING. At a conference held in 2002 at Utrecht, the Swedish National Road Administration (Vagverket) reported on the results of a training program for light-duty vehicles.
About 1000 drivers were trained in Sweden on how to drive in ECODRIVE manner, and fuel consumption on a fixed circuit was measured before and after training. The decrease in fuel consumption measured was about 12 to 13%. Long-term follow-up indicated that fuel consumption decreases in real traffic were in the 5 to 10% range. Most of the drivers were commercial drivers and their employers had a strong incentive to save money.

[vasudeva]

Data from California Air Resources Board 9CARB) indicates that fuel economy impacts are directly related to the power of the cars, more specifically to the horsepower/curb weight (HP/WT) ratio. The The results imply that for a powerful (HP/WT ratio over 50 HP per 1000 lbs./450kg) car, the fuel economy penalty for aggressive urban driving is minimal, but for those cars with a lower HP/WT ratio, the penalty can be significant. For a typical US family sedan whose HP/WT ratio is around 0.04, it appears that aggressive driving at city speeds causes a 6% fuel economy penalty.

Of course, cars in India have a even lower HP/WT (lb) ratio. Santro has approx. 0.034
, City DSI has 0.031, etc.

[docard]

thanks Mitun and Ram. I thought it will cause some problems thanks again

[RajaTaurus]

Good info Vasu,
Cedia Spirit has 0.043, which means less impact due to aggressive driving..
Makes sense...

[vasudeva]

Originally Posted by RajaTaurus

Good info Vasu,
Cedia Spirit has 0.043, which means less impact due to aggressive driving..
Makes sense...

Refer posts 156 and 157 and connect. For a given car, aggressive driving has a fuel penalty, period.

[arjyamaj]

Hey everyone,

One, thanks GTO, for the wonderful article. Very informative read.

Two, I follow some of these practices myself, pretty much based on common sense and a little bit of wikipedia, the manual etc.
1. Rolling friction- use the rolling friction of the car instead of the brakes when slowing down. This means that you're forced to drive at a lower speed (50-60) as opposed to (70-80). Being in Delhi, I hardly have to use my brakes unless at a traffic signal
2. If I know I have to stop at a signal, I'll put the gear in neutral, turn off my engine and coast to a stop. I know this is slightly unsafe but hey, you should probably be strong enough to handle an alto without power steering. The brakes become less responsive (obviously) but they do work- you just have to press a little harder. Just ensure to put the car in IG II ignition mode(that ensures that all the electricals are on)
3. If I'm coming up on a ramp or a flyover, its pedal to the metal just before beginning the climb- the car generates more momentum that way rather than accelerating up the slope (when its also working against gravity).
4. At the top of the ramp/flyover, I'll again put the gear in neutral, turn off the engine and coast to the bottom by which time I would have enough momentum to keep going for atleast another 100 mtrs (do remember that these are delhi roads). Once I hit a speed of 40, I put the car in gear, and use the momentum to restart the car (I'm told that this ruins the gear box in the long run, but the savings in fuel are well worth it- plus the gear box, like the rest of the car, is insured)
5. Use only high octane fuel- this actually makes a difference. It also makes a difference if you tank up (lesser evaporation space) early in the morning (denser fuel).
6. Idling at red lights is a no no (I have an MPFI 796cc 3 cyl). I turn it off if I have to wait for more than 30 secs.

Now call me a fool for some of those practices above, but I still get a 16-17 kmpl in Delhi city with the ac on.

Am considering changing the stock tyres to tubeless alloys, a K&N filter and an FFE. Am told (and this thread says so too!) that these actually help you.

Comments??? Suggestions?

[prabuddhadg]

Arjyamaj, you are taking too many risks. I wouldn't turn off the ignition when the car is in motion.

[GTO]

2. If I know I have to stop at a signal, I'll put the gear in neutral, turn off my engine and coast to a stop. I know this is slightly unsafe but hey, you should probably be strong enough to handle an alto without power steering. The brakes become less responsive (obviously) but they do work- you just have to press a little harder. Just ensure to put the car in IG II ignition mode(that ensures that all the electricals are on)

I'll again put the gear in neutral, turn off the engine and coast to the bottom by which time I would have enough momentum to keep going for atleast another 100 mtrs (do remember that these are delhi roads).

Please DONT! Your life (and that of others on the road) is far more valuable than the coupla drops of fuel that you save in this way. I cant be more serious than this, please do not resort to such extreme measures in saving petrol. If you are so keen on saving $$$, buy a bike or better yet...walk.

(I'm told that this ruins the gear box in the long run, but the savings in fuel are well worth it- plus the gear box, like the rest of the car, is insured)

Incorrect. The gearbox is not insured against wear and tear. It is covered by warranty, but only for a limited period.

[rahuldeodhar]

Hey - this is risky - I am all for turning engine off at long signals - but not while approaching the signal itself!! - agree with GTO totally !!

You take care dude!

RD

[Xehaust]

Dont turn off the car unless at signals that are over a minute long at least.
Else, all you are doing is saving a few ruppees worth of fuel but your car wear and tear is increasing by leaps & bounds. The amount of fuel saved when engine is turned off at a signal of 45-60 secs, the engine drinks it up while starting so there is nil savings. Also, it is not advisable to turn off the engine very frequently as it increases engine wear and tear by leaps and bounds.

Hope this dissuades you from turning you engine off while driving. It is very very dangerous and you dont save much anyways. Like stated by GTO, if you are very fuel conscious,then buy a bike, walk for short distances and take a cab for long ones. Use your car only occasionally.

Would conclude by saying that in the long run, your not saving anything as the amount saved on fuel is easily taken over by the amount of wear and tear on your car in the long run. Specially as mentioned by you - on the brakes and the gearbox.