1.9 dci (130) Poor fuel economy.

[bill j]

I drive about 30000 miles a year mainly on motorways so decided to buy my first diesel since everyone bangs on about good economy, car runs good but only gets 40 mpg at best on the motorway. (Book says 48+) I thought it might be down to being a new tight engine, but now have 8000 mile on it and it's still hasn't improved. dealer said cold weather effects economy. (new one on me) Anybody have similar problems? and is this normal. Now feel i should stick with petrol as it's cheaper all things considered.

[Mikey G]

Diesels take a lot longer to 'loosen up' than petrol engines. How did you run it in? Opinions vary on this but it seems to be the case of drive them as you would normally from the off and they return better mpg sooner than rather than later.

Cold does affect diesels a lot as the fuel is slightly thicker and so doesnt combust as well.

[busta]

I did 1000 miles in a 1.9 dci 120 laguna last year and averaged 48 mpg. Thats was with hard driving (it wasn't my car!), cruising at a ton most of the time, saw over 130 a couple of times (on particularily long stretches of private motorway )

The car had done 70k though, so maybe that's where the difference is.

Also where do you fill up? Ive noticed significantly worse fuel consumption when I fill up at supermarkets. In the laguna we stuck to Shell and BP.

[IRM]

run a laguna 175 gt (06 plate @ 34000) and get 40 mpg drive it like my hair is on fire

does it come with climate and if it does do you have it on ? as i know that can affect economy
noticed a drop to 38 over winter with it on a the temp turned to 26 degrees c

like you its getting to the point of why have derv with that economy

that being said i've hired an 07 mondeo st tdci with 1800 mls for this weekend and that only does 42 mpg

[bill j]

Mikey G said:

Diesels take a lot longer to 'loosen up' than petrol engines. How did you run it in? Opinions vary on this but it seems to be the case of drive them as you would normally from the off and they return better mpg sooner than rather than later.

Cold does affect diesels a lot as the fuel is slightly thicker and so doesnt combust as well.

Yes i did run it in. (old habbits) gentle for first 1000 miles then moderately till 3500 miles and that was on motorways so when you think about it it is probably covered the equivelent to a 1000 or so local stop / start miles. Just hope things improve with age.

[tigger1]

Is that in a Laguna or a Megane?

Not sure, depends how they're driven really - but I managed to get over 50mpg on M1 / M25 over the weekend, with some very brisk sections. That was 5-up in a 106dci Megane (8000 miles), certainly wasn't being gentle with it.

How are the tyre pressures?

Air con?

Are you really really obese (sorry, just kidding!)

[bill j]

tigger1 said:

Is that in a Laguna or a Megane?

Not sure, depends how they're driven really - but I managed to get over 50mpg on M1 / M25 over the weekend, with some very brisk sections. That was 5-up in a 106dci Megane (8000 miles), certainly wasn't being gentle with it.

How are the tyre pressures?

Air con?

Are you really really obese (sorry, just kidding!)

It's a scenic megan, have air con off, tyre pressures good and i am not heavy on the throttle, in fact the throttle pedal is hardly depressed when cruising so it's not like the engine is being held back by anything like binding brakes or the like. In the past i have always obtained the stated combined MPG on various cars but this one is like 10 mpg off the mark.

[tigger1]

http://uk.cars.yahoo.com/car-reviews/

suggests (urban) 38.7mpg / (extra urban) 53.3mpg / (combined) 47.1mpg - so you're 40mpg doesn't sound that wide of the mark. I know the most I generally get from my 106bhp megane is 55mpg (extra-urban stated as about 60mpg I think). Age will still likely be an issue.

[smhmotorsport]

bill j said:

tigger1 said:

Is that in a Laguna or a Megane?

Not sure, depends how they're driven really - but I managed to get over 50mpg on M1 / M25 over the weekend, with some very brisk sections. That was 5-up in a 106dci Megane (8000 miles), certainly wasn't being gentle with it.

How are the tyre pressures?

Air con?

Are you really really obese (sorry, just kidding!)

It's a scenic megan, have air con off, tyre pressures good and i am not heavy on the throttle, in fact the throttle pedal is hardly depressed when cruising so it's not like the engine is being held back by anything like binding brakes or the like. In the past i have always obtained the stated combined MPG on various cars but this one is like 10 mpg off the mark.

Bill, Ive a diesel Scenic, what are you basing the figures on? The on board computer or filling/emptying the tank? The missus drives it now but I seem to remember getting around 600-650 miles a tank without being too hard on the acceleration. The computer on these things gives an average from when reset, so if you hoof it for 10-20 miles it will show as a lower overal figure. I found it would show around 60mpg on long journeys but got obsessed with trying to get beter and better figures and in the end stopped looking at it. Id say fill it up, reset the trip, and drive it till the light comes on. Do the same again and work out from there rather than the on-board figure.

[AntMat]

Economy drops in winter becasue of increased alternator load % time. Warming up takes far longer too as it is a TWAT (Thin Wall Alloy Technology) engine That is to say that you will be using more electrics more often. This will increase the load on the alternator.

The engine won't be fully loosened until 12 - 15,000 miles and if you're too easy on it you could glaze the bores. Stick helps to keep the EGR valve operating more efficientl which is the key to improved consumption on TDs!

[ooral]

Anyone else driving it? 18 year old son for example? Just wondering, my mpg hits the floor when someone borrows the diesel!