Fuel Economy Query.

[alan1304]

Hi everybody.
This is not a problem, just a query. When I tell friends and relatives that I'm getting 35 mpg from my 1998 W202 C180 Esprit Auto Petrol, they look at me as if I have lost my mind, with mutterings of "Can't get that sort of economy from an 1800 Automatic.... especially one that's 16 years old".
So to prove it, (more to myself than anything else) I took a note of the mileage. Put £11.00 worth of petrol in the car and took the wife and one of my 16 year old twins to Paignton for a couple of hours. I don't drive like an idiot so cruised all the way there and back at 60 - 70 mph. Checked the mileage when I got back, 67.6 miles. Considering petrol down here is just about £6.00 a gallon I calculate that £11.00 worth of petrol is just under two gallons, which to my way of thinking is approximately 35 mpg.
I'm just wondering now what kind of mileage other W202 owners are getting.
I'd be interested in your replies.

 

[Sp!ke]

I would expect that you could get that sort of mpg on a gentle run but probably high twenties on average.

You cant get an accurate calculation by putting £11 in the tank. What you need to do is fill it to the brim, reset the trip meter and drive it until you hit reserve and then brim the tank again, making a note of how many liters you put in.

 

[alan1304]

Hi Spike,
I know £11.00 wasn't enough to do an accurate test, but the way I look at it, that run was done for 20 miles on the A38, so that would be cruising at 60 - 70, and the last 10 miles into Paignton, (First 10 coming back.... obviously) were country roads so 30 - 40. So a pretty good average run. I did the same calculations last year after a holiday to Southampton and got the same result, so it does seem pretty accurate.

 

[markjay]

I don't think the figure you mention is unreasonable at all.

MPG depends very much on your driving style and road and traffic conditions.

My car is a W203 C180K and similar to yours has a 1.8L engine with automatic transmission, and on a gentle 15 minutes run at 50mph on the A40 with little traffic returned over 45mpg, which is impressive (even assuming that the on-board computer may not be accurate).

This is of course not sustainable in everyday driving, roads are rarely free to allow us to cruise at 50mph endlessly - but 35mpg is actually quite reasonable for a moderately driven 1.8L car if you manage to avoid traffic.

 

[alan1304]

Thanks markjay. That is VERY good mpg. It's nice to know that Merc have managed to shake off the image of being gas guzzlers. My father always liked the Mercs of the '60s and '70s but wouldn't have one because they were expensive to run and keep on the road. I think the newer ranges of cars is showing just how much times have changed.

 

[kth286]

I would expect that you could get that sort of mpg on a gentle run but probably high twenties on average.

You cant get an accurate calculation by putting £11 in the tank. What you need to do is fill it to the brim, reset the trip meter and drive it until you hit reserve and then brim the tank again, making a note of how many liters you put in.

Instead of people getting the idea that you have to use a full tank of petrol to
do a mpg test, I would say that to do a spot check, you need only drive a few miles, (say 20 miles with engine up to temp) and replenish the tank to the brim.

Then do your calcs based on that.

The basis of the calcs will be the same; but it will be less representative than more comprehensive use over prolonged time/distance.

I feel that measuring mpg over short journeys with a cold engine is pretty useless. All cars will perform badly at that.

 

[alan1304]

I did forget to mention that when I put the £11.00 in, the reserve light had just come on. I must have traveled about 50 yards with the light on. When I got back from Paignton, the light came on again as I was turning around to park outside my house, so I think we can safely say that it takes £11.00 to travel 67.6 miles in my car.

 

[jonc78]

That figure is very good. The best I have ever got was 34mpg, all motorways from Germany. Average around town was about 25mpg but now the car gets used only for short journeys by my wife, it's getting 22mpg and that will of course get lower in the colder months of the year. The fuel economy of this car was one of the main reasons I brought a small diesel when I got a different job and my annual mileage tripled. I do however still love driving it when I get the chance at weekends.

 

[IanA2]

I had a 1995 202 also, but a 2.2l I would have thought it's consumption would be the same/less than the 1.8l From memory, running between Bath and Wembley used to be about 28mph.

 

[BTB 500]

Instead of people getting the idea that you have to use a full tank of petrol to
do a mpg test, I would say that to do a spot check, you need only drive a few miles, (say 20 miles with engine up to temp) and replenish the tank to the brim.

The point is that it's actually very difficult to 'brim' a tank to exactly the same level each time.

A slight discrepancy in fill level will have a minimal effect if you measure consumption across a whole tankful (perhaps 60 litres), but a large effect if you have only done 20 miles (using just 2.5 litres).

 

[219]

35mpg seems perfectly reasonable to me .

Since I got my 190E 1.8 a few weeks ago I have brimmed the tank a few times to see how it is doing . Even with the minor running fault ( poor hot start performance for a few minutes ) it seems to be returning around 35 mpg , with a best of 42 mpg on one long run to Aberdeen and back , keeping to a steady speed between 60 and 70 mph , and a worst of 32 mpg when a little town or stop/start driving is thrown into the mix . This with auto transmission too . The car has been recently serviced by myself with all new ignition components and filters , but I'm not yet certain the injection is optimally set up .

With a previous 190E , with the 2 litre engine , I once averaged 43 mpg across three tanks full , most of that being a round trip to Wales and the return journey being laden with car parts , including a roof rack - again cruising within but close to the legal limit .

I can also remember getting 25 mpg from my 500SEL on long motorway runs .

I think the secret is to keep cars well maintained and to drive with a little forethought and sympathy .

 

[markjay]

MPG figures are very difficult to work out if the journey involves any stops, even for traffic lights or pedestrian crossing.

When stationary, the vehicle's MPG is... zero. This will have an adverse effect on the average MPG regardless of engine size or fuel type (unless it's a stop-start engine obviously).

So if comparing fuel consumption between two cars they should both be constantly rolling while the measurements are being taken.

As said my 45+ MPG was achieved while driving on the A40, and if anyone is surprised then this is because almost all 'day-to-day' MPG calculations involve periods when the car is stationary and the zero MPG will drag down the average figure. .

 

[mbenz1]

Well done to your W202 petrol... My dads 280 CDI took about an hours drive at about 70 mph cruising to reach 40 mpg... These petrol MB engines are just magical....

 

[mbenz1]

I don't think the figure you mention is unreasonable at all.

MPG depends very much on your driving style and road and traffic conditions.

My car is a W203 C180K and similar to yours has a 1.8L engine with automatic transmission, and on a gentle 15 minutes run at 50mph on the A40 with little traffic returned over 45mpg, which is impressive (even assuming that the on-board computer may not be accurate).

This is of course not sustainable in everyday driving, roads are rarely free to allow us to cruise at 50mph endlessly - but 35mpg is actually quite reasonable for a moderately driven 1.8L car if you manage to avoid traffic.

Never seen a figure like that in the trip computer of the ex 280 CDI or the current 320 CDI... That 1.8 Supercharged engine is a pure piece of respectable engineering!

 

[Touche]

My dads old w202 c200 gets around 37mpg on the motorway based on the last 2k miles. I've not done very much town driving in it (father in law is driving it at the moment) so dunno how it does there. It feels about on par with my 2009 Lexus diesel which only gets around 35mpg combined. Overall pretty economical for the car's age.

 

[PJH]

Just driven mid-Essex to Dorset in Wifey's W204 C180K, highest MPG I saw was 47.3 but this dropped to 45.8 near end of journey due to roller coaster roads. Really surprised that a C180K was so economical. Wifey usually gets 29.5 driving locally.
I wonder what a C220 CDI would have returned ?

 

[theogeor]

Petrol cars even bigs ones can be economical from time to time. Last week I had to drive from NW London to Birmingham City Centre. I left at about the right time in London to avoid any traffic going out of London (just before 7:00) and left Birmingham at around 16;00 before traffic started. Total MPG for the round trip was over 28MPG and that is with my Porsche 911/997. Yes I was lucky I did not find any traffic and most of the time I was cursing at an economical speed for the car and did not have to accelerate or decelerate for most of the trip in the motorway. Even in Birmingham the traffic was flowing fine Another important factor is that I was alone in the car so no extra weight and outside temp was about right for fuel efficiency
Dont get me wrong it take luck and effort to achieve that but it also demonstrate that petrol cars in the right conditions are not as bad as people think they are

Theo

 

[kth286]

The point is that it's actually very difficult to 'brim' a tank to exactly the same level each time.

A slight discrepancy in fill level will have a minimal effect if you measure consumption across a whole tankful (perhaps 60 litres), but a large effect if you have only done 20 miles (using just 2.5 litres).

As long as you go back to same pump and use same hose, it's going to cut out at same level as previously.

 

[BTB 500]

As long as you go back to same pump and use same hose, it's going to cut out at same level as previously.

Not sure that's the case - things like the angle you hold the nozzle at can affect how soon it cuts out (certainly true of our vehicles).

 

[kianok]

Not sure that's the case - things like the angle you hold the nozzle at can affect how soon it cuts out (certainly true of our vehicles).

Put it in at the same angle then