Fuel Economy Reporting Thread

AdrianHi

Right now is the only time of year I get near the official combined 47mpg on my for for my daily commute, half an hour of A roads and country roads. I'm getting 46mpg over the last two tank fulls. I think it is partly down to minimising the use of the air conditioning (is is auto matic climate control I leave on all the time) and perhaps because the turbo intercooler is optimised for this temperature (circa 15DegC).
Additionally to get this I use Miller Diesel Power Sport 4 diesel fuel additive, which has the same affect as BP Ultimate Diesel / Shell V Power, but at a 2.5p per litre premium instead of 6-7p per litre extra. I get around a 5% to 7% improvement in MPG using this, saving me about £80 a year over 14K miles.
The rest of my driving style is anticipating the road ahead to minimise braking, getting the foot off the accelerator early and slowing without brakes. I also use the peak torque range of the turbo diesel engine 2000-3500 rpm to get up to top gear and cruising speed ASAP where the car is most efficient. Changing up too early and being too light on the accelerator just means you spend mroe time in a lower gear which is less efficient.
Also never coast out of gear, this uses fuel, if you keep the engine turning over with the motion of the car in gear accelerator not pressed no fuel is used at all.

sillygoose

Today coming down the M1 it was pretty busy so nothing to be gained swapping around the lanes so I did what I usually do, find a good gap between trucks in the inside lane, set cruise to 56-59mph (match the trucks) so I don't need to overtake, brake or accelerate. My Honda Accord pulls happily in 6th at 1600rpm. Over 45 miles from the M18 split to the A42 junction I averaged 76mpg. Very low stress too - just point in a straight line and and the odd tweak of the cruise control buttons. Trying to keep up with the faster traffic which constantly speeds up and slows down and would be lucky to average 70mph 40-45mpg it took just over 6 minutes longer this way, or 2 tunes on my cranked up radio another way to look at it!

tomstickland

I'm seeing if I can reduce fuel consumption by 10% due to more careful driving style.

I believe that the biggest savings are to be made on slowing down.
As an extreme, take for example a motorway junction. From 70mph you could probably roll for a mile to come to standstill at the top of the slip road. Running the engine with no throttle consumes no fuel (overrun). Hence that deceleration distance is free.
I've started slowing down for junctions or slower traffic much earlier.
Say I'm now managing 1/4 of mile "free" for each stop and there are 10 of them each way to work. That's a few miles for free on a 20 mile round trip.
Hence I hope to save around 10% by this and a few other things.

jeferey

After experimenting with faster acceleration to terminal speed, I have found that for me (and my 2.2 diesel) it is more fuel efficient to accelerate steadily without going over 2000 rpm and get it into cruise control as soon as possible. I have averaged 52 mpg for my last 2 fill ups using this technique and keeping the speed below 70mph (usually 50-60). This compares with the official figures for my car of 44.8!
I have also experimented with rolling down hills in and out of gear and the best technique for saving fuel depends on the road - e.g. if you do not need to control your speed leave it in neutral as you will be able to coast 2 - 3 times further otherwise the fuel cut-off while coasting will save you fuel you just won't be able to coast as far due to engine braking.

ihatecharges

I have a BMW 118i with Efficient Dynamics (2 litre petrol) and I get between 47-48 on my daily commute which includes the following.

6 miles urban
15 miles Motorway
7 miles hilly A&B roads

I recently did a trip to Liverpool and back and achieved 50.4mpg, not bad for a 2.0 litre petrol IMHO

This is achieved driving carefully but if I do out my foot down it very rarely drops below 40mpg

samd

pennypilot wrote: »

Hi Martin:money: , Great Item.
A few points about buying fuel; most fuel is stored underground at filling stations and will be at a constant temperature (cool). The exceptions to this are when a delivery is made from above ground storage facilities such as distribution depots or refineries. This fuel will be warm at best and if you live close to a refinery it might well be hot! It will be gaseous and agitated and as such when it has cooled and settled in your tank it will have shrunk. Oil companies run their tankers day and night. If possible try and avoid filling after a delivery. If you happen to live close to a refinery try and fill as far away as possible or move.
On the subject of measurement, 'the best pump to use is the busiest pump' wear in the pump mechanism will allow some 'over measure' to occur. Also try not to run the pump 'flat out' this could effect the measure. The busy pump is the one closest to the shop door.
If you intend to use full tank measures in your calculations you should use the same nozzle on the same pump and stop at the first click. The conversion factor for gallons to litres is 4.54609 to be accurate. Good luck.

Or you could just chill out a little and spend some time relaxing?

AdrianHi

ihatecharges wrote: »

I have a BMW 118i with Efficient Dynamics (2 litre petrol) and I get between 47-48 on my daily commute which includes the following.

6 miles urban
15 miles Motorway
7 miles hilly A&B roads

I recently did a trip to Liverpool and back and achieved 50.4mpg, not bad for a 2.0 litre petrol IMHO

This is achieved driving carefully but if I do out my foot down it very rarely drops below 40mpg

... and you get 0-62mph in 8.7 seconds.
The Prius doesn't even get a look in with figures like this :cool:

jeferey

Interesting article in The Times recently -

Fuel prices: how to save £500 a year (even if it does mean driving at 20mph)

Link: http://driving.timesonline.co.uk/tol/life_and_style/driving/article4107764.ece?&EMC-Bltn=LXJA49

ihatecharges

AdrianHi wrote: »

... and you get 0-62mph in 8.7 seconds.
The Prius doesn't even get a look in with figures like this :cool:

I know, it's great isn't it!

I have read many articles about the Prius and everyone will have a difference of opinion on this so I do not want to go off topic but I do not think they are as 'green' as the Manufacturers claim!

klint

Quoting from that web page: "He found that a Citroën C4 1.6 diesel achieved 99.6mpg at 20mph". I find it hard to believe that 20mph is the optimum speed. I don't know about diesels, but my petrol-powered car would struggle to get into 4th gear, let alone top. I would have thought you would at least have to be in top, with high enough revs to avoid labouring the engine, to attain best economy. Unless, of course, the C4 they tested had such bad aerodynamics that drag was the most important factor.