Increasing fuel savings

chavvdarrr: that can be very different with different cars. 4th gear at 60kmh is more economic in most cases because of lower rpm, but driving uphill like that will probably be less economic. In general, lower rpm is in most cases more economic.
 
if I'm at 60kph or even less on 4th gear, getting outside of a town for example, I'll accelerate very slowly (very slight added pressure on the pedal), I get the feeling I should do that at such low rpm. it's not like it takes ages to reach the legal 90kph.

better to downshift if you have to or want to accelerate faster, or climb a steep hill. if there's only one steep hill on my way my car will be happy to climb it fast on the low gears, fuck fuel efficiency for a short while :p
but if there are dozens of them I won't necessarily get to the legal speed, fuck the cars being me.
 
_xxx_ said:
chavvdarrr: that can be very different with different cars. 4th gear at 60kmh is more economic in most cases because of lower rpm, but driving uphill like that will probably be less economic. In general, lower rpm is in most cases more economic.
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geee, I got it right this time :D, just that almost every day I pass a 2-3km long plane road, ( at the exit of the city) where the road is fine, no much cars, yet possibility of walkers is relatively high and the reasonable speed is just in that spot - a bit high for 3rd, a bit low for 4th ;)
 
I'd say that as long as you don't need to give the car more than a tiny bit of gas, run the car as close to idle rpm's as possible. Just be sure to downshift before attempting to accelerate.
 
hmm,

interesting about "putting in neutral' and coasting.. this is claimed to be false by my cars manual, though this maybe as its a manual not automatic. the theory is thus.
in neutral, the engine must actually run in order to tick over. if you go are moving in gear , but not accelerating, the fuel is actually cut down to a lower amount than 'idle' would need because the motion of the car is keeping it going..
 
Yup, that's what I thought, too. However, it is conceivable that at higher rpm's, the friction in the engine will cause the car to slow down more than the gas required to keep the engine at 1k rpm.
 
I would typically expect SUV's to have about the highest threshold speed, since their aerodynamics aren't good to begin with. I'd wager that there's going to be much more of a difference to the aerodynamics of a Camaro at 50mph than a Suburban if each opened their windows.
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Well, the thing wasn't really the aerodynamics difference as that isn't so absolute as a relation to the vehicle. For instance, the windows all the way open on a Camaro is still a pretty small profile.

The point was more about how much of a load the A/C is against the engine, and I wasn't really comparing to an highly powered sports car, but say, a little econobox like the Fit (or Jazz in EU), which still has a pretty hefty A/C compressor, so the relative load of the A/C on the engine is greater, which means that with the windows open the power load of drag on such a small vehicle scales up at a lower rate with respect to speed (because power of drag is also related to Cd and profile size).

This is as compared to a big SUV where load of drag scales up quicker, and the engine has enough power that the A/C is less of a load (relatively speaking).
 
Alright I know this might not be adding much to the conversation here (which is an excellent topic IMO) but the best advice for us Brits to save money on fuel is to move to America!

Secondly would be probably.. buy a smaller engine modern car (not a KIA or similar).

Thirdly would be.. walk!

Petrol (or gas as you Americans call it) prices in the UK are mad... almost £1.00 (approx $1.75) to the LITRE!! Ouchers!

P.S. I coast when I can these days and try not to drive aggressively...
 
Chalnoth said:
Walk? Bah, who walks? Ride a bike!

(seriously, I fill up my tank maybe once a month, as I ride my bike to campus).
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I rode my bike 13 miles to pick up my car from the shop today :) It was fun but took a long time not to mention it is hot (of course my car was in the shop to have the AC fixed :) )
 
Tahir2 said:
Alright I know this might not be adding much to the conversation here (which is an excellent topic IMO) but the best advice for us Brits to save money on fuel is to move to America!
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But doesn't the airplane to get to your work in Britain get expensive?
Of course you'll get lots of frequent flyer miles :)

Tahir2 said:
Secondly would be probably.. buy a smaller engine modern car (not a KIA or similar).
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Ehm, what exactly should be wrong with KIA?

Tahir2 said:
Thirdly would be.. walk!
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Let's just stick to realistic options :)

Tahir2 said:
Petrol (or gas as you Americans call it) prices in the UK are mad... almost £1.00 (approx $1.75) to the LITRE!! Ouchers!

P.S. I coast when I can these days and try not to drive aggressively...
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Is LPG not an viable option in the UK?
That really saves me a lot!

And avoiding traffic jams saves LOTS of fuel too. (unfortunately it is often quite difficult)
 
_xxx_ said:
It's crap? :devilish:
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While I agree with you, there is something fundamentally wrong with pushing 1500kg of steel and plastic around to haul 75kgs of largely lard and water wherever it needs to go.

I know plastic cars has been a dead end in the past. But once oil hits >$100 per barrel consumer perception might change :)

Cheers
 
Too bad they didn't do proper real-life tests.

Then they would have discovered that their claims that you can save lots of fuel are all bogus!

I tried most of them myself when I had a car which accurately measured fuel consumption.
My results:

* aggresive driving.
They are wrong about the reason it takes more fuel. Accelerating fast isn't all that bad for fuel consumption. You are just creating potential energy that you later use when coasting. The effect on fuel consumption is minimal.
The real fuel consumption killers are your brakes (strange as it may sound)
When you brake you waste all that energy. You cannot use it in any way anymore. That's why braking hurts the fuel usage so terrible.
The problem with aggressive driving is that it usually means people brake more too. But if you just accelerate fast, but don't brake more or harder than the people that drive moderately you won't spend measurably more fuel.

* lower speeds save gas.
That's true on the highways. (and especially in Germany at 110mph :))
But it's not true with lower speeds. The reason is that air friction stops being a important factor with lower speeds. (40mph for example)

But do you really want to drive slowly on highways? The whole reason for having these things is so you can drive faster.

Their advise is to stick to the speed limit. Why not 10 mph below the speed limit? You'll save even more gas that way....

* Cruise Control
I don't know about you guys, but I also drive smoothly without cruise control. Anybody who has earned their drivers license should already be doing that.
I save absolutely NOTHING by using cruise control !

Of course cruise control makes driving a lot more comfortable, so I always use it. But that's a different discussion.

* AC.
Well enough said about that already. In my current car it takes 5% fuel consumption. In the car before that (a bit smaller) it took 10%.
But I don't want to exchange safety and a huge comfort increase for just 5% less fuel consumption.

* Tire pressure.
My own experience is also that it saves almost nothing. Certainly not if you just stick to recommended level and above.

* Excessive idling.
Nice results in their test, but not applicable to real-life at all!
They drove 10 miles, stopping 10 times for two minutes.
Just think about that. Who has ever experienced such a situation in their life?


Conclusion:
When I use their advice in real life I can save little to nothing!
 
Gubbi said:
While I agree with you, there is something fundamentally wrong with pushing 1500kg of steel and plastic around to haul 75kgs of largely lard and water wherever it needs to go.

I know plastic cars has been a dead end in the past. But once oil hits >$100 per barrel consumer perception might change :)

Cheers
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What models are you guys talking about and to what are you comparing it?

Must be very special "heavy-plastic" KIA is using in Europe, because their cars are just as heavy as the competition.
Reliability is not as good as japanese cars, but certainly as good as european and american cars.

Lots of their models LOOK crap (especially the interior) but I don't think he meant that.
 
OpenGL guy said:
Diesels gain efficiency because detonation happens everywhere simultaneous, but, with a regular gas engine, detonation begins at the spark plug.
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I thought by now an adiabatic engine, using a homogeneous air/gasoline mixture, would be possible. Such a design allowed for complete combustion as the flame front travelled throughout the chamber. IIRC, Smokey Yunick had an interesting idea but it was impractical due to heat/wear issues. Perhaps material science will soon be able to address the issues.
 
I wonder how much efficieny would be gained by that. I think people might be disappointed.

Afaik the efficiency of Diesel is mainly caused by the higher compression.
(which is also the reason for the extra pollution. Although I realize that that is not an issue for the americans here ;-))
 
Gubbi said:
While I agree with you, there is something fundamentally wrong with pushing 1500kg of steel and plastic around to haul 75kgs of largely lard and water wherever it needs to go.
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I was joking of course, they're cheap so it's a healthy case of getting what you pay for.
 
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