Fuel economy - anyone beating the official figures?
Discussion
Chedder. Your dad is under a complete misapprehension that putting any car into neutral while going downhill will save fuel. IT WILL NOT!!!!!!
Putting it into neutral means that the engine is ticking over - and therefore using fuel. The ONLY way to save fuel while going downhill is to leave the car in the highest gear and take your foot completely OFF the throttle. The electronics in the vehicle completely cuts off the fuel supply to the engine, thereby using NO fuel whatsoever. As soon as you touch the throttle fuel will again be supplied to the engine.
I would imagine that most of the people who have replied to this posting quoting fuel consumption figures are misguidedly using the figures that are given out via the dashboard. It is in the manufacturers interest to make those figures look as good as possible - and just like the VW "defeat device" fitted that got VW into so much trouble, none of those dashboard readouts should be treated as the absolute truth.
The ONLY way to correctly work out fuel consumption on any vehicle is to fill the vehicle with fuel right to the very top and note the mileage. After 300-500 miles, (keep a note of the exact mileage), fill the vehicle in the same way and note how many litre's you've used. Lets say 36.5 litre's. Divide 36.5 by 4.546, (this is how many litre's make a gallon). This will equal 8.191 gallons. Lets say you've done 476 miles. Divide 476 by 8.19. This will give you an MPG figure of 58.11.
The above is the MOST ACCURATE way of working out the fuel consumption of any vehicle, and just like anyone being stupid enough to believe the manufacturers published MPG figures for ANY vehicle - your computer readout should also be treated with the self same scepticism.
Putting it into neutral means that the engine is ticking over - and therefore using fuel. The ONLY way to save fuel while going downhill is to leave the car in the highest gear and take your foot completely OFF the throttle. The electronics in the vehicle completely cuts off the fuel supply to the engine, thereby using NO fuel whatsoever. As soon as you touch the throttle fuel will again be supplied to the engine.
I would imagine that most of the people who have replied to this posting quoting fuel consumption figures are misguidedly using the figures that are given out via the dashboard. It is in the manufacturers interest to make those figures look as good as possible - and just like the VW "defeat device" fitted that got VW into so much trouble, none of those dashboard readouts should be treated as the absolute truth.
The ONLY way to correctly work out fuel consumption on any vehicle is to fill the vehicle with fuel right to the very top and note the mileage. After 300-500 miles, (keep a note of the exact mileage), fill the vehicle in the same way and note how many litre's you've used. Lets say 36.5 litre's. Divide 36.5 by 4.546, (this is how many litre's make a gallon). This will equal 8.191 gallons. Lets say you've done 476 miles. Divide 476 by 8.19. This will give you an MPG figure of 58.11.
The above is the MOST ACCURATE way of working out the fuel consumption of any vehicle, and just like anyone being stupid enough to believe the manufacturers published MPG figures for ANY vehicle - your computer readout should also be treated with the self same scepticism.
raspy said:
Toyota GB claim my Prius will do 94mpg. I usually exceed that when the engine is warm, as in this morning's trip.
However, it's only getting 75mpg average per tank, which is significantly lower than 94! I wish they put realistic figures in the brochure.
They're only allowed to quote the figures from the NEDC testing, nothing else.However, it's only getting 75mpg average per tank, which is significantly lower than 94! I wish they put realistic figures in the brochure.
It would be a useful metric to have a steady-state cruise economy at 120km/h for example, but they can't.
Dog Star said:
cheddar said:
Dog Star said:
SLK diesel
150mph
70mpg
750miles on a tank.
Must be right up there on 'top speed/economy' graph150mph
70mpg
750miles on a tank.
I smell a potential new thread
I'm impressed at your mpg, given the official figure of 56.5 you've beaten it by over 25% and It'd be hard to find a non hybrid car that can hit 150mph or 70mpg
datum77 said:
Chedder. Your dad is under a complete misapprehension that putting any car into neutral while going downhill will save fuel. IT WILL NOT
The ONLY way to correctly work out fuel consumption on any vehicle is to fill the vehicle with fuel right to the very top and note the mileage.
The above is the MOST ACCURATE way of working out the fuel consumption of any vehicle
To be honest datum I don't know if he coasts in neutral or not but he does drive for economy and loves his figures, he's far more likely to tell me how few rpm his car needs to pull smoothly in 6th than his highest top speed, he quotes brim to brim average mpg to four decimal places and never uses the obc as his reference. The ONLY way to correctly work out fuel consumption on any vehicle is to fill the vehicle with fuel right to the very top and note the mileage.
The above is the MOST ACCURATE way of working out the fuel consumption of any vehicle
He's an ex test driver for mainstream manufacturers and kind of knows his stuff, probably best to avoid a dinner invite with him unless that's your thing :-)
cheddar said:
datum77 said:
Chedder. Your dad is under a complete misapprehension that putting any car into neutral while going downhill will save fuel. IT WILL NOT
The ONLY way to correctly work out fuel consumption on any vehicle is to fill the vehicle with fuel right to the very top and note the mileage.
The above is the MOST ACCURATE way of working out the fuel consumption of any vehicle
To be honest datum I don't know if he coasts in neutral or not but he does drive for economy and loves his figures, he's far more likely to tell me how few rpm his car needs to pull smoothly in 6th than his highest top speed, he quotes brim to brim average mpg to four decimal places and never uses the obc as his reference. The ONLY way to correctly work out fuel consumption on any vehicle is to fill the vehicle with fuel right to the very top and note the mileage.
The above is the MOST ACCURATE way of working out the fuel consumption of any vehicle
He's an ex test driver for mainstream manufacturers and kind of knows his stuff, probably best to avoid a dinner invite with him unless that's your thing :-)
Some cars used this on purpose by having a freewheel in the transmission- eg a Saab 96 (although that was a hangover from its 2 stroke days).
cheddar said:
My father reckons that overall he's 4mpg up on the manufacturers claimed mpg in his Skoda Octavia, no mean feat given that most of us struggle to get within 20% of the 'official' figures.
He's a real 'neutral downhill' and 'into 6th before he's out of the driveway' type so it's possible.
Anyone else manage this?
I think this depends on how old the car in question is. If it's 10, 15 or 20 years old. Then the claimed figures are probably different and easier to attain.He's a real 'neutral downhill' and 'into 6th before he's out of the driveway' type so it's possible.
Anyone else manage this?
Modern cars absolutely maximise the NEDC test and will generally be much harder to match in real life. Also there are 3 figures typically quoted, Urban, Extra Urban and Combined. Which can vary considerably.
cheddar said:
To be honest datum I don't know if he coasts in neutral or not but he does drive for economy and loves his figures, he's far more likely to tell me how few rpm his car needs to pull smoothly in 6th than his highest top speed, he quotes brim to brim average mpg to four decimal places and never uses the obc as his reference.
He's an ex test driver for mainstream manufacturers and kind of knows his stuff, probably best to avoid a dinner invite with him unless that's your thing :-)
Got to side with your dad on this one (sounds like he has expert credentials anyway). Would like an authoritative answer but any time there is engine braking I highly suspect the energy converted from the forward motion to engine losses is more than the small amount of fuel used when idling in neutral. If there's no engine braking effect as in latest DSGs then sure, leaving it in gear best of all worlds.He's an ex test driver for mainstream manufacturers and kind of knows his stuff, probably best to avoid a dinner invite with him unless that's your thing :-)
LHRFlightman said:
I car share with a guy who has a 2015 A Class Mercedes, the 1.5 diesel i think it is.
Over 15,000 he's averaging 84mpg. If we have a clear run, A331, M3, M25 to Heathrow, we regularly see over 95mpg.
All that on the OBC.
Not bad for a Renault engine......must be fun racking up that mpg Over 15,000 he's averaging 84mpg. If we have a clear run, A331, M3, M25 to Heathrow, we regularly see over 95mpg.
All that on the OBC.
donkmeister said:
2004 E500, official motorway figure is 37.7mpg, i can get 36.5 on a short motorway cruise without much effort... One day I'll try to beat 37.7 but it's a boring way to drive.
Similar to my 2011 CLS 350 petrol. 40.something combined officially. I regularly see 42-43mpg on a long run to London. Helped by a bit of 50mph average speed, but normally cruise is on at 77mph or so and I get 39-41mpg on the same 100 mile journey. Big capacity engines with good motorway gearing always produce better than expected figures if driven the right way 
datum77 said:
I would imagine that most of the people who have replied to this posting quoting fuel consumption figures are misguidedly using the figures that are given out via the dashboard. It is in the manufacturers interest to make those figures look as good as possible - and just like the VW "defeat device" fitted that got VW into so much trouble, none of those dashboard readouts should be treated as the absolute truth.
Yes, indeed. I know from comparing my hand calculations on a tank that the dash mpg for my car is between 7-10% optimistic. Hey ho.
Yes, indeed. I know from comparing my hand calculations on a tank that the dash mpg for my car is between 7-10% optimistic. Hey ho.
Targarama said:
Similar to my 2011 CLS 350 petrol. 40.something combined officially. I regularly see 42-43mpg on a long run to London. Helped by a bit of 50mph average speed, but normally cruise is on at 77mph or so and I get 39-41mpg on the same 100 mile journey. Big capacity engines with good motorway gearing always produce better than expected figures if driven the right way
Imho you are daft to buy the big diesel engines, the petrols get within 85-90% of them and so, so, so much nicer. M1C said:
My 9-5 Aero did approx 30mpg average, with a low of 19.2 on a hoon, to 46mpg on a 60mph cruise. I think the quoted combined as 30.7mpg.
Wow... So mine (Stage 3 auto estate [~320bhp]) varies from a low of 18 (average 20~ish doing 4 miles a day), to 27/28 on a cruise at 75/80. Average over the year reaches mid 20's.I just fill it up when needed (mapped for v power) but like to keep track.
Lazadude said:
Fast-forward to today, do I REALLY want to see how much motion lotion my 4.4 V8 Rangie is consuming?
The (admittedly rhetorical) answer is a resounding NO!
The M140i will frequently venture up into the 40s (combined 39.8) on a longer run if you stick to the speed limits.
One example below is at the end of a 155 mile round trip to a client a few weeks back. Busy roads for a few miles to the motorway, quiet-ish motorway, into a busy town centre for the meeting, then back again. Drive selector in default Comfort mode (cannot stand Eco Pro), transmission in normal auto mode, air-con on all the way (it was hot) and just "driving normally".
Staggering for a turbocharged 3 litre petrol auto, IMHO.
Car is averaging 29.4 mpg over 4500 miles (computer says 30.1 so fairly accurate). If I drove it sensibly all the time I reckon I could get the average into the mid 30s, easily. But what would be the point? :P
One example below is at the end of a 155 mile round trip to a client a few weeks back. Busy roads for a few miles to the motorway, quiet-ish motorway, into a busy town centre for the meeting, then back again. Drive selector in default Comfort mode (cannot stand Eco Pro), transmission in normal auto mode, air-con on all the way (it was hot) and just "driving normally".
Staggering for a turbocharged 3 litre petrol auto, IMHO.
Car is averaging 29.4 mpg over 4500 miles (computer says 30.1 so fairly accurate). If I drove it sensibly all the time I reckon I could get the average into the mid 30s, easily. But what would be the point? :P
Edited by Limpet on Thursday 29th June 14:52
LHRFlightman said:
I car share with a guy who has a 2015 A Class Mercedes, the 1.5 diesel i think it is.
Over 15,000 he's averaging 84mpg. If we have a clear run, A331, M3, M25 to Heathrow, we regularly see over 95mpg.
All that on the OBC.
Thats excellent! That'll be the Renault engine. If thats on he OBD, it may not be doing those figures but still, they'll be up there.Over 15,000 he's averaging 84mpg. If we have a clear run, A331, M3, M25 to Heathrow, we regularly see over 95mpg.
All that on the OBC.
My highest displayed mpg figure for any decent length of time (i.e not resetting down a hill) is 75mpg on a 2002 Yaris 1.4 diesel.
Gassing Station | General Gassing | Top of Page | What's New | My Stuff