C220 cdi mpg experiment

[Clemster]

Hi,

I commute 104 miles a day and as such I decided to see how easy it was to increase my MPG while still living in the real world. My commute comprises of driving two different routes, the drive to work is around 17 miles on an A road and the remainder on the M27. The return journey is Motorway and dual carriageway. This is because when I go to work at 0600 the A road is quiet but on the way home the morning route would travel through Salisbury and the rush hour traffic is stop and start so it is easier but longer to stay on the motorway/Dual carriageway.

The basic theory is to keep the car moving at a uniform speed so basically very little stopping and starting.

I tried the journey so that when I was on the Motorway and Dual Carriageway I would use cruise and stay at 70 MPH. I filled the car and reset the trip monitors. By doing the journey for the week at 70 MPH the car was averaging 47.9 MPG. Not bad at all for a large saloon that is automatic.

The next week I refilled the car and reset the trip monitors but this time when on the Motorway and Dual Carriageway I set the cruise at 60 MPH. The car sits at about 1700 rpm but when I looked at the average the car was showing 59 - 61 MPG!! I will try a few weeks at 60 MPH to see what this levels out at but by simply dropping 10 MPH I have gained nearly 14 MPG!! Fantastic!!

Clemster

 

[E320mark]

I think a lot of people will be starting to do this now! In reality it is the only way we can save any money at the pumps. Mine on a long run at 65 has been as high as 41mpg, not bad for my car. Will try 60 on my next run in a few weeks and see what happends!

 

[jberks]

Is that 59-61 at the pumps or off the computer - quite remarkable if its at the pumps - questionable if thats what the computer says.
Acceleration and braking are what uses fuel. Maintaining 60 or 70 takes almost nothing. Just enough to compensate for friction which is minimal, especially if you don't have the silly fat tyres many of us run around on. I guess by maintaining 60, you have much less need to brake, plus you're not accelerating as much.

I know If I drive more gently and leave a bit of a gap to allow me to slow by dropping the throttle rather than touching the brake, my MPG improves dramatically.

 

[M80]

Agreed I think we will see many more efficiency minded cruisers on the m'ways now.

I've always tried to be efficient with the Jeep (2.7 Merc CDI engine) as it's easy to see 22mpg on the obc (worst actual 21.3 mpg) .

I generally cruise at 57 - 58 on the m'way, a bit slower would be more frugal but then I'm slowing HGV's and generally being a nuisance.

Yesterday over 320 miles (filled at the start and just filled again ready for tomorrow) the actual was 33.8 mpg, ****** marvelous for that motor.

Across Derbyshire 30 mile to M1, up past Doncaster, over the Ilkley (nth Yorks a mix of M, A road and rural), down to M/cr, over to Prestatyn (M and A road) and Home.

Yesterday's fill £6.09 per gal, today's £6.13, makes you wonder about tomorrow.

 

[Clemster]

Hi,
The figure that I am quoting is from the computer on the car. I used the computer on both occasions. As I continue with this experiment I will be taking a tally on how much it costs each week to fill as the trips are the same week in week out.

That said, you are right on not having to stop and start a lot. by sticking to 60 Mph and staying in lane 1 the rest of the world just passes by and it is quite amusing to see people pass and then you see them again a little later on as they yo yo in lane two and three with then rushing up to traffic and then having to slow down and accelerate again. I have found that I don't have to touch the pedals as the car just stays at a steady momentum.

Another benefit so far has been less road rage. Basically because I am not racing up to cars and not being able to pass so have to slow down and accelerate all of the time i can just sit back and relax and let the world go by.

I reckon that my total journey time is an extra ten mins if that.

This is early days but I will post regularly and that way we can work oout a real time average.

regards
Clemster

 

[dieselman]

Sounds about right, driving 16% slower giving 25% better economy.
How much longer has the journey taken?

Time for some aerodynamic mods and Eco tyres as most of your journey is constant speed driving.
Try blanking most, if not all of the grille for starters, just ensure the engine intake can get fresh air.

You can be our test Mule.

 

[Rappey69]

Half term, now there is a time that my mpg shot up whilst driving at same cruising speed, just not getting snarled up in stationary traffic !

 

[st4]

I think a lot of people will be starting to do this now! In reality it is the only way we can save any money at the pumps. Mine on a long run at 65 has been as high as 41mpg, not bad for my car. Will try 60 on my next run in a few weeks and see what happends!

On a long run at 50-60mph mine has been at 46mpg. At 70 this is 42-43mpg. The increase in speed is greater % wise than the decrease in consumption.

Your car should be doing a bit better

 

[HKG3A3]

My cdi tonight just managed 44mpg on a 19 mile trip, and thats with a dodgy thermostat....

I Use the tip tronic to knock it up a gear over the auto....:neutral:

 

[st4]

My cdi tonight just managed 44mpg on a 19 mile trip, and thats with a dodgy thermostat....

I Use the tip tronic to knock it up a gear over the auto....:neutral:

Good man, I found that with mine is that it would pull a higher gear than the box electronics thought it would.

 

[skyline1241]

I think a lot of people will be starting to do this now! In reality it is the only way we can save any money at the pumps. Mine on a long run at 65 has been as high as 41mpg, not bad for my car. Will try 60 on my next run in a few weeks and see what happends!

I also think so.
__________________
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[HKG3A3]

Good man, I found that with mine is that it would pull a higher gear than the box electronics thought it would.

....Plus if i lost about 8 stone, that would help my cosumption:Oops:

What a good engine though, returning those figures and the power and torque it has is impresive.

 

[MrGoose]

Auto Driving Technique

Had the C270 CDI three weeks and still getting used to an Auto box. Not sure I really like it to be honest.

Getting around 42 MPG running 15 miles to work and back with the gearbox in "C" mode driving steadily.

A short run from Leeds to Helmsley maybe 40 miles showed 51.8 MPG steady away.

I find myself flicking the gear lever to get an up change all the time and it seems to do it in most cases, the engine is certainly gutsy enough to pull the higher gear. I also find myself knocking the lever to neutral at the lights if its a long wait.

An i missing the point of an auto box or do you guys find yourselves doing the same.

 

[M80]

Good man, I found that with mine is that it would pull a higher gear than the box electronics thought it would.

I think consumption would be better if it wasn't changing through 7 gears though.

At a push I can get the 320 into 7th at about 45, the car would rather wait. Annoying is that going down any slight incline and it drops gears.

I've noticed that as the box would drop gears at a pinch it's sometimes best to let it stay lower geared till a higher speed, then there's less energy lost changing gear.

 

[Alex M Grieve]

Had the C270 CDI three weeks and still getting used to an Auto box. Not sure I really like it to be honest.

Getting around 42 MPG running 15 miles to work and back with the gearbox in "C" mode driving steadily.

A short run from Leeds to Helmsley maybe 40 miles showed 51.8 MPG steady away.

I find myself flicking the gear lever to get an up change all the time and it seems to do it in most cases, the engine is certainly gutsy enough to pull the higher gear. I also find myself knocking the lever to neutral at the lights if its a long wait.

An i missing the point of an auto box or do you guys find yourselves doing the same.

It is just a matter of getting used to it. Driving in "C" mode, it will give earlier upchanges than the other option, so you are "in the right gear".

Instead of flicking the gear lever for an up change, try easing your foot on the throttle which will enable the change up if you are going quickly enough and not puling hard up hill for example at the time. With a little practice it will become second nature.

Do remember that MBs are programmed to hold the lower gears longer on a cold engine to facilitate engine warming, so for the first mile or so, it might prefer the lower gear anyway, and that is what it is supposed to do.

I think most people, even the manual gearbox zealots, find automatics so restful that they wondered why they didn't change sooner.

 

[dieselman]

An i missing the point of an auto box or do you guys find yourselves doing the same.

I find myself leaving it in D all the time...well for the last ten years or so anyway..

 

[Alex M Grieve]

Annoying is that going down any slight incline and it drops gears.

More recent Cruise Control will certainly do this Martin - which is good for keeping you legal in a speed limited area with a steep downhill.

Older versions did not either change down or brake, so you must be wary of the speed creeping up even if you are on CC.

 

[dieselman]

I think consumption would be better if it wasn't changing through 7 gears though.

7 speeds should help economy as the engine should always be close to it's peak torque figure.
Is moving to a higher gear definitely assisting with economy or is it pushing the engine below it's efficiency range of revs?
You can't really tell because annoyingly Mercedes don't utilise the instantaneous mpg readout, but fitting a Scangauge or Kiwi MPG would reveal all.

My car will change into the next gear at 1500rpm or over and is happy to hold that down to about 1100rpm, so I just leave it.

 

[M80]

7 speeds should help economy as the engine should always be close to it's peak torque figure.
Is moving to a higher gear definitely assisting with economy or is it pushing the engine below it's efficiency range of revs?
You can't really tell because annoyingly Mercedes don't utilise the instantaneous mpg readout, but fitting a Scangauge or Kiwi MPG would reveal all.

My car will change into the next gear at 1500rpm or over and is happy to hold that down to about 1100rpm, so I just leave it.

It's an interesting theory of offset that I have considered.
As you say I can' t know for sure.

With the available torque of a larger engine often the peak isn't required, steady flat cruising for example. The transmission still hangs on to a lower gear, rather than dropping the revs.

I am open to correction, but doesn't the auto use energy for each change ? So 7 instead of 5 consumes more energy ??

Edit Excuse my more than normal mistakes, I'm filling my face prior to driving down to Nothampton.

 

[dieselman]

Selecting a higher gear when under light load will assist economy, but as I find in Mrs Dm's car, dropping out of the bottom of the efficient rev range does no favours at all when even the slightest increase in torque is required.
That car is only happy down to about 1500rpm.

The best way to get decent economy isn't to drive slower once moving, but to ensure you never stop moving and when accelerating just gradually build speed, allowing the box to change up at the lowest possible revs, rather than accelerating even moderately quickly.
Observing most drivers, they tend to accelerate briskly in the first few gears then tail off the speed. That won't help at all.

For those with only the average economy meter, try an instantaneous gauge, you will save fuel as a result.