Safe Speed Forums

When accelerating from standing start to a normal journey speed (lets say 56mph), for example joining a NSL DC on a slip road, or leaving traffic lights, which is better in terms of wear & tear, fuel consumption, any other factors:

1. Hard acceleration to the required travelling speed, then back off the throttle
2. Gentle acceleration all the way
3. Some combination of the above
4. sitting in the back seat of a big fancy limo with a fresh mint julep prepared by a dusky maiden

Alright, the last isn't presently an option until that nice Mr. Abago Ubogu sends those millions of Nigerian Oil Dollars into my account ...

(for the purposes of the discussion - assume completely flat road)

(posted in this forum as a 'driving' question).

Andy

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If I could afford number 4 I wouldn't care less about economy!

My car is a turbo diesel and I reckon that flooring it uses loads of fuel and too little accelerator doesn't get the turbo spinning soon enough to be efficient. As long as the engine is doing over 1500 rpm it is quite happy. So I think somewhere between 1. and 2. is a good compromise.

The thing to remember though is that it's brakes that waste all your fuel. Everytime you touch the brakes all that kinetic energy gained from burning fuel gets turned into heat, so plan ahead and minimise the braking.

My tuppence:

Engines are at their most efficient near max torque (N/A) at around half of max revs. This means you need to put your foot down to get the best efficiency. The bigger your engine, the quicker you’ll have to go! This assumes the clutch isn’t overly slipped. So for fuel efficiency I would be more inclined towards 1

Wear and tear is accelerated by excessive torque or engine revs, so for this I would opt for 2

The fuel saved by higher torque acceleration will be offset by the extra wear on other components (transmission, tyres, clutch) but by how much I don’t know.

I suspect you're right about the best answer being a compromise between options 1 and 2, but it probably depends on the particular model of car.

As for braking, I would imagine most drivers could make quite useful gains in fuel economy simply by learning to be more skilled in their use of the little pedal on the right.

Best wishes all,
Dave.

Fairly hard acceleration but gear changes at middling revs.

I like to be on my own on the road with lots of room in front and behind so sometimes 1 and sometimes 2 and even 3 if is means finding a space on my own.

As for 4 I am afraid you are too late Mr. Abago Ubogu sent his millions to me, you should've been a bit quicker answering his E-mails.

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Burn & Coast!

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The IAM will tend to encourage you to accelerate briskly (not brutally) up to your desired cruising speed and, obviously depending on the vehicle, to block upchange from third to fifth.

Letting the engine labour in high gears will result in much slower acceleration and not in practice save fuel.

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"Show me someone who says that they have never exceeded a speed limit, and I'll show you a liar, or a menace." (Austin Williams - Director, Transport Research Group)

Any views expressed in this post are personal opinions and may not represent the views of Safe Speed