Fortunately I don’t have a money man checking to see how much fuel I use but I had a long (for me) run back from Poole today and I started tinkering with the fuel computer &cruise control. By looking at the instant fuel consumption readings at different constant speeds I noticed that knocking the speed back from 89 to 87 Km/h seemed to make a noticable difference.
Other speeds gave other results but 87km/h was a definate winner.
I set the cruise at 89km/h and zeroed the trip and drove for 20k or so and noted the consumption, then zeroed it again with the cruise set to 87 and drove another 20k or so. I did each three times and got similar results.
Each of the runs was under more or less the same conditions, no hills to speak of, lightly loaded, no stopping / starting or changing speed in fact it was almost entirely without doing anything but steering.
At 89km/h it was doing about 10.5mpg, knocking it back to 87km/h changed the figure to about 12mpg.
I was quite surprised that the difference was 10%, If the bean counters start checking fuel I know how I can suddenly improve
But for those who are tightly watched it’s worth trying out.
You will save a good bit of fuel. You will also feel less stressed once you reach your destination and it doesn’t really make a huge to your overall journey time either.
damoq:
You will save a good bit of fuel. You will also feel less stressed once you reach your destination and it doesn’t really make a huge to your overall journey time either.
Another advantage is that you are not constantly staring at the same cab as he tries to overtake, knock it back 3 or 4 clicks, and I bet when you get to the end of the motorway that vehicle will be a couple of yards in front of you
Much of it is due to wind resistance, I do regular runs along a flat stretch of the M62 and on a calm day at 52 mph I can
see 10 mpg, add a head wind and it’s down to 7 mpg but up to 12 mpg on the return journey.
That’s an FH13, 520 towing a fridge.
I could see much more out of our DAF XF 95 480, sometimes just under 14 mpg with a following wind.
Another sure way to save fuel, if you are bothered, is not to join in the drag race at every set of traffic lights.
I realise that a lot of drivers don’t care but the truck uses a huge amount of fuel getting away from a standing start
and simply putting the accelerator to the floor just makes it worse.
I read on here, it costs £5 in fuel to get from 0 to 56 mph, the way I see some driven, more like £5 0 to 30 mph.
I could understand it if there was a prize for the winner but in the end, no one wins.
You will only be stressed if you miss your slot to load or tip and have to spend a night out when you have loads of drive time left still if you got 8 mpg whats the ,…,.,.,.,.,
A subbie we use a lot has a Scania 8wheeler and he will not go above 50 anymore. I rarely go above 50 and get around 10 mpg. An identical Foden is generally driven at 56 as much as possible and does 7.5.
fuse:
You will only be stressed if you miss your slot to load or tip and have to spend a night out when you have loads of drive time left still if you got 8 mpg whats the ,…,.,.,.,.,
50,000 miles @ 8 mpg = 6250 gallons.
50,000 miles @ 10 mpg=5000 gallons.
At an optimistic but easy to work out £5 a gallon, the difference
of 1250 gallons is £6250.
Ten vehicles = £62,500 etc, etc.
No wonder some of the big fleets are limited to 52 mph.
I tested 87kmph for about 2 months and found that mpg was loads better,
best in a small fleet consitently and journey times were hardly any different,
maybe 5 - 10 mins on a 2.5 hour run, never missed a slot unless it was impossible
to start with.
fuse:
You will only be stressed if you miss your slot to load or tip and have to spend a night out when you have loads of drive time left still if you got 8 mpg whats the ,…,.,.,.,.,
You’ve still got that extra 2 or 3mph to up your sleeve if you are that pushed for time on the odd occasion.
I did also try some lower speeds but it was using more fuel. 87km/h deffo seemed the speed but obviously that is specific to the individual vehicle.
I don’t generally get stressed as I don’t worry about the fuel and don’t tend to travel any great distances, however whilst trying to maintain a constant speed today over 20 odd K’s it was doing my brain in trundling past slower vehicles, when I knew there was a bit extra on tap.
I was purely doing it out of interest and wanted to keep everything as controlled as possible.
Normal foot to the floor behaviour resumes tomorrow though
I am very interested in this at the moment, with the cost of fuel about to rocket, but what is the optimum speed, i dont want the guys to crawl around, but with no hope of any rate rises, the only option is to try and improve the mpg, we run fh 12420 and 460 and man, a 440 and a euro 3 460.I think this will be crucial in the coming future, one truck last week cone £1500 in fuel, single shifted, anything to improve will help.
As in most EU States the Maximum Speed is 80 Km/h why Manufacturer fit Axles which run best just under the 50 mph. try driving with 47/48 mph and you may be on the Maximum you can do to be most economical
Immigrant:
As in most EU States the Maximum Speed is 80 Km/h why Manufacturer fit Axles which run best just under the 50 mph. try driving with 47/48 mph and you may be on the Maximum you can do to be most economical
Our Volvo Fes back this point up; Anymore than 49mph and you start leaving the green band.
richmond:
I am very interested in this at the moment, with the cost of fuel about to rocket, but what is the optimum speed, i dont want the guys to crawl around, but with no hope of any rate rises, the only option is to try and improve the mpg, we run fh 12420 and 460 and man, a 440 and a euro 3 460.I think this will be crucial in the coming future, one truck last week cone £1500 in fuel, single shifted, anything to improve will help.
I’d have thought that giving the driver an incentive to acheive better mpg is a good start. If they can save £50 / week on fuel give them £15 of it, that sort of thing. That might be tricky with some f your work being odd shape and size etc.
I’d suggest something similar to my outfit as the average my R420 8x2 does is only about 7.2mpg, it spends a fair bit of time idling, a fair bit on PTO and generally isn’t doing a lot of constant speed distance work. I could easily improve that as I tend to leave the engine running and PTO on whilst I load / unload rather than drop the ramps, turn engine off, load and then restart before raising the ramps. That sort of thing would make a bit of difference. My lot don’t seem bother about the fuel usage, but if I suggested that I could improve it they’d probably expect me to anyway and probably impose some sort of penalty for not doing so.
I run a Merc 460,I pull a crane trl behind it so not verry aerodynamic,I’m also running at 44t 75 percent of the time,I travel various routes up and down the country,I run at 82 kmh/50mph and no more I don’t race of the lights n generally come of the gas when ever possible buy doing this I’m averaging 7.5 mpg which I’m v happy with,drive the thing like an idiot n it all average 6.8mpg i pay for the fuel so I look at it as more beer tokens for the weekend
If you just want to get good MPG then basicly the slower the better given that most of the energy used is wasted as air resistance (providing you are with in the efficient working limits of the mechanical parts) so probably around 30-40mph,
In terms of family car drag coefficients the fuel consumption increses exponentialy with speed, once you reach speeds above 50mph the fuel consumption increses drasticaly.
For a truck with the far less aero dynamic shape i would say the tipping point is about 40mph
the formula for drag is below
Drag force = (1/2)p(v^2)Cd*A
As you can see speed v is squared hence the exponential increse
Cd is the drag coefficient witch is dependant upon the shape
(I am a mechanical engineering student BTW looking for HGV work to fill up my spare time (and because I enjoy driving))
AHT:
If you just want to get good MPG then basicly the slower the better given that most of the energy used is wasted as air resistance (providing you are with in the efficient working limits of the mechanical parts) so probably around 30-40mph,
In terms of family car drag coefficients the fuel consumption increses exponentialy with speed, once you reach speeds above 50mph the fuel consumption increses drasticaly.
For a truck with the far less aero dynamic shape i would say the tipping point is about 40mph
the formula for drag is below
Drag force = (1/2)p(v^2)Cd*A
As you can see speed v is squared hence the exponential increse
Cd is the drag coefficient witch is dependant upon the shape
(I am a mechanical engineering student BTW looking for HGV work to fill up my spare time (and because I enjoy driving))
Suppose we’ll just have to take your word for that theory AHT!!!
In normal language, I think what he is trying to say is, if you are pulling a loaded decker, without a sloping roof and you have no air deflector on your tractor you are pretty much screwed if you go over 40mph in the hope of getting 12mpg.
