E350d Terrible mpg SOLVED

[OneForTheRoad]

I've also ordered 4 new tyres rated A for fuel economy, made by an Irish company called ' Ironic '

 

[E55BOF]

Isn't that a Hyundai model?

More seriously, I too wondered whether this thread was an ad for Terraclean, but I'm not sure. Is there actually an electrical connection to the thermostat, and if so, what for? If there is, and it's for coolant temperature sensing, fair enough, I suppose, but if not, the OP's statement doesn't make much sense to me.

 

[OneForTheRoad]

Isn't that a Hyundai model?

I went to have a look at 1 , there was a Q.

 

[E55BOF]

That was a Toyota...

 

[W1ghty]

Isn't that a Hyundai model?

More seriously, I too wondered whether this thread was an ad for Terraclean, but I'm not sure. Is there actually an electrical connection to the thermostat, and if so, what for? If there is, and it's for coolant temperature sensing, fair enough, I suppose, but if not, the OP's statement doesn't make much sense to me.

Electrical connection on a thermostat is a new one on me (but lots of stuff is )

 

[Daddyoftwo]

It's not an advert for Terraclean and I'll post a photo of the speedo display when I next do a similar journey

I think you mean 20psi?
20 Bar is approximately 280 psi!

Yes - sorry meant 20psi

 

[Daddyoftwo]

I think he was having a joke, you would need to change the engine not just the thermostat to get that mpg.

I'll post a photo of the speedo next time that I do a similar run. It was on an empty motorway at 70mph for about 10 miles and about two miles back to my house. Obviously not going to be exactly the same mpg as I said. It's not an advert for TerraClean - I have just had it done twice now on my cars and found the initial results astonishing but they wore off very quickly. With this I think that the thermostat cable was the main cause. But I've gone from appalling to better than Manufacturer's claimed.

 

[Daddyoftwo]

Sounds like an advert for Terraclean.
How did the thermostat register 95 degrees without being connected?
But agree fuel economy would definetly improve if thermostat was faulty, but to increase by 60% is pretty much unbelievable.

I think that there is a separate temperature sensor at the back of the car in addition to the thermostat. I am not a mechanic - but the guy at the garage (who was not an MB mechanic) said to me that if the thermostat was not sending messages to the ECU that it was open then it could really muck up the economy.

I suspect that that it might also have been full of carbon from a few years of running too long at cold when the thermostat seal had been perished. Hopefully the TerraClean removed some / most of that.

 

[Rory]

It probably takes 5 of those 8 miles to warm up ?

More than that in any diesel - on rolling A road driving, mine's well into the teens of miles before it's fully warmed up. Wife has a newish diesel VW Tiguan - that shows 90C on the water temp after 3 miles, but it'll also show the oil temp. At 3 miles there's no reading for the oil temp! Again, low teens of miles to get the oil to 90C.

 

[TeddyRuxpin]

My OM642 E350 has an electrical connector on the thermostat, yes. And it's pretty hard to miss on the OM642, it's right there are the front and top of the engine, a big shiny silver thing.

The electrical sensor is why the bloody thing is so expensive.

 

[Daddyoftwo]

 

[Daddyoftwo]

View attachment 109285

You'll just have to take my word that I got 59mpg on the dash on a midnight blast a few days ago on the same route.

There were far more cars this afternoon so I couldn't keep up a steady speed and I had to stop a few times coming back off the motorway. Doing 70mph on motorway on average (+ - 10 mph) and not very flat and a couple of miles off motorway on 30 / 40mph roads. This was after car was heated up.

From cold, ie from "Start", and the 18mile round trip, it was about 45mpg but that included a bit of Italian tune up before hitting reset on the return leg. But even this was good for a 3.0litre diesel.

I'm not boasting about fantastic economy - merely stating how I've solved the terrible economy. Before this would have been about 38mpg instead of in the mid 50s.

 

[Daddyoftwo]

You'll just h

 

[Daddyoftwo]

Just saying check your thermostats if you get terrible economy - especially as mine didn't throw up any engine lights, or error codes in my £20 eBay OBD2 reader. And temperature on guage looked reasonable.
... and if that was the problem, then you might need to use something like TerraClean to get the cruddie carbon out.

 

[Daddyoftwo]

Also - my feet were always a bit toasty on Automatic at 21° even at 20° climate (and especially when I had the roof down and heating up). A bit early to say but this seems to have gone away. Maybe that 3.0l lump of diesel 12 inches in front of my feet was a bit too hot before.

 

[geoffus]

. It's not an advert for TerraClean - I have just had it done twice now on my cars and found the initial results astonishing but they wore off very quickly.

How can the results wear off very quickly?

 

[OneForTheRoad]

How can the results wear off very quickly?

Pixie dust isn't eternal.

 

[geoffus]

Pixie dust isn't eternal.

Your disbelief has caused a baby unicorn to die, shame on you.

 

[Daddyoftwo]

How can the results wear off very quickly?

No idea. I just know that on my Jag a couple of days afterwards after Terracleaning, I had to make a 200 journey, it was pretty icy and a lot of 60mph average speed limits but I got over 70mpg and looking at it the next morning I had a flattish tyre. That was amazing for a 2.2d heavy estate. It had done about 140k. Then the economy went down to getting about 50mpg on a run which was still superb. Over the next 55k / 4 years of ownership it went down to getting about low 40s mpg which was still good.

TerraClean suggest cleaning every 15000 miles. I thought that was a bit of a sales thing to get it done more than necessary. But maybe I'll spend the £130 every two years.

 

[Daddyoftwo]

How can the results wear off very quickly?

No idea. I just know that on my Jag a couple of days afterwards after Terracleaning, I had to make a 200 journey, it was pretty icy and a lot of 60mph average speed but I got over 70mpg and looking at it the next morning I had a flattish tyre. That was amazing for a 2.2d heavy estate. It had done about 140k. Then the economy went down to getting about 50mpg on a run which which was still superb. Over the next 55k / 4 years of ownership it went down to getting about low 40s mpg which was still good for a car with nearly 200k on the clock.

TerraClean suggest cleaning every 15000 miles. I thought that was a bit of a sales thing to get it done more than necessary. But maybe I'll spend the £130 every two years.