Fuel economy in motor way driving
- Thread starter ferrelscent
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talking of whichDaffy said:
http://en.wikipedia.org/wiki/Fuel_economy-maximizing_behaviors
http://en.wikipedia.org/wiki/Drafting_%28racing%29#Drafting_for_efficiency_on_the_road
Some drivers have been known to draft behind other vehicles, particularly tailgating larger vehicles, to save fuel. For example, hypermilers using this technique can achieve 75 mpg or more.[6] Some sources say that the most common tailgating does not save gasoline even at freeway speeds because one is likely to accelerate and brake so frequently that any aerodynamic savings are lost through the brakes.[7] On the show Mythbusters, drafting behind an 18-wheeler truck was tested and results showed that traveling 100 feet (30 m) behind the truck increased overall mpg efficiency by 11%. Traveling 10 feet (3.0 m) behind the truck produced a 39% gain in efficiency. Of course, they warn that this type of driving "is insane" because the truck's blindspot is in that area, and if the truck stops quickly there is much less time to react.[8] Truckers are not fond of the extra stress this puts on them, worrying about cars on their tail. Additionally, it can be very dangerous for the following car if one of the truck's tires (or their recaps) delaminate, as the chunks of ejected rubber can be large enough to cause serious harm, even death, to a driver following too close.
Eco driving isn't the zeds strong suit...on the rare occasions I've decided to go in the "slow" lane on a motorway run for any period of time I've found it considerably more stressful due to the sheer speed and number of vehicles overtaking. I'd rather accept some minor mpg loss and go for a progressive approach and, other than letting the odd madman through at 100+, stick to the outer lane.
Interesting, I think i'll stick to 70+ though. I spend enough time at 56 in the truck and that is not out of choice, it's dangerous to do low speed, especially in a small car and moreso in poor visibility or bad weather where if you are doing similar speeds to trucks you are much less likely to be seen or end up sitting in a blind spot, particularly with foreign trucks. Fuel economy is one thing, safety is another.
I'll be pretty happy if I average 30mpg+ in general, it's what I expected to get. I'm trying out various fuels at the moment to see if I get any noticeable difference in economy from 95, 97 and 98, so far it appears to make no difference, RON numbers are all a bit sketchy anyway, US 'premium' fuel is a whopping 91.
I'll be pretty happy if I average 30mpg+ in general, it's what I expected to get. I'm trying out various fuels at the moment to see if I get any noticeable difference in economy from 95, 97 and 98, so far it appears to make no difference, RON numbers are all a bit sketchy anyway, US 'premium' fuel is a whopping 91.
fraserbottomley
Member
I find mine (2.5 N52) is most fuel efficient cruising at about 2200 rpm - can't remember what speed that equates to in sixth, probably about 60?! Even though it pulls cleanly (doesn't labour) from about 1500 rpm .
I think different engines will have different speeds for best MPG. The 'M' seems to produce best figures at about 65 in 6th. Any slower and the engine labours. I've managed 34 MPG average on a trip from Liverpool to the Cotwolds which is pretty impressive ( and very boring!) for such a powerful engine!
I mostly agree, but you don't have to sit behind a truck, you can sit in front of them.Kiowan said:
And yes, in bad conditions I concentrate on the road more, but you're probably going to be going at a lower more economical speed anyway in bad conditions, and you'll be wanting to keep more distance between vehicles as well, so all that helps you whether you're aiming for economy or not
cj10jeeper said:
I've read the same before as makers tune the torque/power to be most economical at the Euro MPG test speeds, the other benchmark being 76mph.
I have a boring motorway commute in my daily driver so tried approx 65 mph for a week then about 75 and consistently got an extra 4-5 mpg at the HIGHER SPEED of 75. At erhm 80 it gives the same as 65, but havn't got the stomach to do a week at 56mph on the motorway!
I assume because it's a six speed it's over-geared at the lower speeds. Top tip, drive faster and use less fuel
benlumley said:
In the average speed bit on the southbound M1 (think its around 10miles long) at 50 mph roof up my ODBC said 46mpg. On the way back up with the roof down (windows up seat heaters on first setting) i got 39 mpg... but then it might be more uphill.... but my car would have been lighter with less petrol!
The traffic conditions were also different.
Well i'm jealous. Changed my base of operations at the beginning of the year and now do some motorway driving each way to and from work . My fuel economy has dropped from 27.9 to 25.4mpg. The route is more up and down so although the home trip is more economical i am doing more costly driving daily, 1st and second gear driving in a 35i isn't that economical. I do about 22000 miles a year. Long trips on the motorway are great and visiting friends in St Albans returns a mid thirties fuel consumption for the trip.
Only saving grace is that my front tyres have now done 27500 miles with life still in them. Got 23500 out of the rears then had a puncture in one, runflats so no repair
And before anyone says anything, yes my rev counter has hit the redline on more than one occasion :wink:
Only saving grace is that my front tyres have now done 27500 miles with life still in them. Got 23500 out of the rears then had a puncture in one, runflats so no repair
And before anyone says anything, yes my rev counter has hit the redline on more than one occasion :wink:
Blackadder
New member
Hey,
New to this forum and thinking of getting a Z4 SDrive 23i (2010).
Just wanted to get some "real World" view on likely fuel economy.
My typical week is:
3 days commute 70 miles each way, mostly on motorways (total: 420) - cruising about 80mph
Rest of the week and weekends is town driving (c. 75 miles) on A and B roads longest journey maybe 10 miles one way
Just wondered what people's experiences are with this type of driving - roof up and roof down?
Thanks for the help 8)
New to this forum and thinking of getting a Z4 SDrive 23i (2010).
Just wanted to get some "real World" view on likely fuel economy.
My typical week is:
3 days commute 70 miles each way, mostly on motorways (total: 420) - cruising about 80mph
Rest of the week and weekends is town driving (c. 75 miles) on A and B roads longest journey maybe 10 miles one way
Just wondered what people's experiences are with this type of driving - roof up and roof down?
Thanks for the help 8)
I do a mix of motorway (80%) and town, about 500 miles a week, stick the cruise to 73 mph on the motorway and then some enthusiastic motoring at the weekend and I am returning about 36 to 37 mpg (lifetime avg on the trip is 38.1). Fuel economy is about the same between the 2.3 and the 3.0
As for servicing, my first was at 26,000 miles for oil and have an inspection 38,000. Swapped my rear tyres for the fronts at 23,000 miles, and have 3mm on front and 5mm on rears.
It is a great car to do the miles in, better than a tractor at least
As for servicing, my first was at 26,000 miles for oil and have an inspection 38,000. Swapped my rear tyres for the fronts at 23,000 miles, and have 3mm on front and 5mm on rears.
It is a great car to do the miles in, better than a tractor at least
OT, sorry, but FYI, the US uses an average of 2 different octane determination methods, RON and MON. MON is usually 8-10 below the RON method used in the rest of the world, so a US 91 works out to 95 or 96 RON. We still have crap fuel, too much sulphur, but it's not in the octane rating.Kiowan said:
To other North Americans following along, keep in mind imperial gallons are 20% larger than US gallons.
That's all, carry on.