mick replied:

Scoey,

I imagine it would use more. The load would be different, no load as compared to some load. I suppose it would be like riding a pushy, 100 revs per min with no load (exercise bike on min setting) to 100 revs per min up a steep incline.
Same revs different workload, the hill will stuff ya before the excercise bike would.

A bit like changing into top gear to early, low revs but the ole motor is working far harder,

thats my 2 bobs worth!

Mick

Member - Doug T (QLD) replied:

No wind resistance would meen less fuel but....ummm ....why is it running at 1200 rpm in nuetral i thought idle speed was about 700-800 rpm.
Ive seen these old guys [ i'm gettin close too ]about 80yo 3/4 deaf with clutch in and engine screaming at about 3000 revs "ridin the clutch" , your NOT like that are you Scoey.....yet

Michael ( Moss Vale NSW) replied:

1200 rpm under load will have a different throttle position than idle, of course open more, so more fuel will be used. As for the 1200 RPM at speed would only be 50kph I guess so the wind drag on the car would be minimal...Well thats my theory.. Best regards, Al Einstien

3.0turbob replied:

If you apply the factor of the co-efficient of drag of the vehicle at a given tyre pressure (remaining constant), opposed to the friction induced by the surface of the road at it's relative temperature and humidity, then include the barometric pressure of that time of the day, factor in the fuel flow rate, .... then the answer would be ..yes?

..................................................
sorry, should be in the friday funny section
Rob

Dave Thomson replied:

Scoey, the earth spins at 1000 miles an hour {24 hrs in a day 24000 miles an hour}
if you could travel at 25000 miles an hour, would you meet youself coming back ??? We both need to get out more I think,
regards,
Dave
By the way , why do they call flats apartments when they're all together ???

F4Phantom replied:

In a petrol engine if you use engine braking down a hill no matter what the RPM the engine uses ZERO fuel. The butterfly valves are shut and so do the spark plugs, I am actually not sure if the fuel is cut off but it must although I cant see how it would be. Anyway, this is a situation where the engine is under no load, the rpm is high and it uses no fuel. If you reverse this, it's simple, engine under load uses more fuel, more load more fuel. And as already stated about throttle positions add to that computer intervention, my car is sluggish in economy and way faster in sport mode.

Gerhardp1 replied:

I have recently got one of these and it answers all these questions.

www.scanguage.com

Member - Collyn R (WA) replied:

Quick response.

For both petrol and diesel, consumption will be less whilst idling because consumption is related to work being performed. And whilst idling the only load is internal friction, drive belt and fan losses etc. Once the vehicle is moving friction, rolling and wind loads add to the load on the engine - and more fuel in burned.

Whilst idling however a petrol engine is 'throttled down'. That its cylinders are only partially filled with air - and thus its 'effective' compression ratio is reduced. This reduces efficiency and thus increases consumption.

A diesel engine however full cylinder-loads of air almost regardless of speed an/or load. Its effective compression is thus much the same as its nominal compression (of 18:1 - 22:1) throughout most its rev range. This enables its to to run closer to optimum efficiency.

This is part of the reason why diesels are so much more efficient in heavy traffic and whilst slowing traversing dirt tracks etc.
Collyn Rivers