[jaylee]

On June 11 I drove my Nissan Frontier from Tanjung Bungah, Penang to KL
LCCT, averaging 105-115Kph on the PLUS Highway and returning to refuel at
the Petronas Station at Simpang Pulai, I used up 57.502 litres of diesel to
cover the distance of 674.8 Km = 11.735 Km/L (8.522 L/100Km).

Dropping my speed to between 90-95Kph for the distance of 174.1 Km from the
Simpang Pulai Petronas Station to the Tanjong Tokong Petronas Station, I
used 10.991 litres and the fuel consumption dropped dramatically to 15.955
Km/L (6.268 L/100Km) = a whopping 26.4% drop in fuel consumption for a 15%
drop in speed.

In both cases the Penang to LCCT and return to Penang journeys were done
below 5 hours. The distances were calibrated by GPS so they are accurate.

It pays to drive at below 2,500rpm for diesel engines.

[Tourist]

I always tried to drive at 90kph for that exact reason but never really
done the math calculation.

[acetech]

Hi friend,
Yes! That is the optimum speed also a recommended speed for every car not
to exceed 90km/h.
Another word is not exceed 3,000rpm also can achieve fuel saving as well.

Of course, need to include few main factors, such as:-
#1) Road conditions
#2) Quality of fuel
#3) Engine maitenance work
#4) Driving atttidue
#5) Tyre pressure
#6) Quality of lub oil
#7) etc...

[jaylee]

Just to add on, at 95Kph, my engine speed is 2,500rpm.

At 115Kph, the engine speed is 3,000rpm.

It is true that at below 3,000rpm the fuel consumption is lower than above
3,000rpm but the sweet-spot for my car is between 90-95Kph when the engine
speed is between 2,300-2,500rpm. It is also within the range for peak torque.

You should find out what is your car's G ...oops, sweet-spot.

[bm2]

haa jay lee... funny..

I have not gotten my diesel car yet, still processing the paper work. But
I have been driving my 305 much slower since the fuel hike, yes same goes
for petrol cars, consumption is much better - my 305 gets about 20%
better. I also accelarate slower.

I wonder, if the fuel consumption will improve a lot more if we drive at
less optimal but lower RPM? say 2000rpm or 1800 rpm vs 2500rpm? i never
done it, cos it is really really waste of time already.

[jaylee]

Hi bm2,

I am sure you wouldn`t want to drive too slow otherwise it will be cheaper
and maybe even faster to ride a bicycle.

The design of every car is centered around a set of compromises and the key
is to find the optimum - the sweet-spot which gives you the best fuel
economy while achieving a decent speed. The gear ratios and differential
ratios are all chosen to achieve this optimum. Usually, the range of
optimum torque will indicate where this sweet-spot is. Both petrol and
diesel engines will benefit at the sweet-spot but diesel engines will
benefit more by nature of their very design. You cannot drive a petrol
engined car at the same slow rpm as a diesel because the engine will judder
when you are below the effective torque range. Usually petrol engines will
sing above 2,500-3,000 rpm. Diesel engines sing at a much lower rpm. For
example my engine reaches optimum/maximum torque at 2,000 rpm so I can
easily drive without judder at 1,500rpm even on the 5th gear. You can
never do that with petrol engine.

For sure fuel economy will improve with lower engine speed up to a critical
point/speed below which there is no benefit but problems begin to arise.
Above the optimum speed, other factors particularly wind resistance etc.,
will quickly come in to destroy fuel economy.

As I have just found the sweet-spot for my car, my purpose of writing is to
encourage you to find yours. Good luck.

[wen]

new nissan sylphy claims 16 km for 1 liter of petrol, do you believe?

my coming to 12 years old xantia diesel only manage to run 13 km per liter
for long distance, 110km at 2600rpm.

but my car can only be sold 10k while sylphy selling for 113k, and i can
safely buy only 3rd party insurance because no one want it!!!!

[lukeraj]

You are right but lazy to drive slow la try using Fuelstick free samples
are given away for savings and performance

[lukeraj]

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After August the price of the Fuelstick will be RM49.90
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as of today we have sold almost 982 packets to autoworld members at
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We want to thank all of you for your continous support and confidence in
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Cheers

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[Autosyn]

i tried it on 3 cars.. it doesn't work. No fuel savings. Tried it over 3
tanks of fuel..