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I used to run a Toyota Avensis Estate (1.8) that regularly gave a consumption better than the official combined figure of 36.2 mpg. I now run a Citroen C5 Estate (2.0 110 HDI) and cannot get close to the offical combined figure of 49 mpg (44 is about it !). I am completing very similar journeys and still have this problem even when taking more than usual notice of the instantaneous mpg readout. Anyone else having similar problems ?
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The only hope I can offer is sometimes it takes a while to get the best from a diesel, both in terms of running it in and adapting a driving style.
Some folks never adapt and will easily drop their older Xantia 1.9TDs to around 37mpg. Others will happily get 45mpg plus.
How are you getting on with the C5 otherwise?
David
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Out of curiosity, what is considered the 'correct' technique for driving a diesel?
I've driven XUD derivatives for the past 4 years, the latest a Xantia 1.9TD which I rarely get any more than 40mpg out of in normal A-road driving or around 44mpg at motorway speeds.
I had thought perhaps the injectors might need servicing at 122k/5 years to give some improvement, but perhaps its all in the technique!!
Chris
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Am sure many others will offer more comprehensive advice but the trick is to NOT drive the car like a petrol.
The virtue of a diesel engine is high torque at very low engine revs. The automatic reaction is when say, overtaking, to drop the car down a gear. In a petrol this makes sense as the output of the engine is highest in the higher levels of the rev band and at a cruising engine speed much less power and acceleration are available. In a diesel this is not the case and so instead of dropping the car from fourth to third, it will pull just as quickly, if not perhaps more so, in fourth gear - and also use much less fuel doing so. I know a lot of rep drivers who took months to adjust to driving diesels and using low revs consistently and I was often astounded by how they actually could get as little as 30 odd to the gallon from a diesel Mondeo etc!
Takes a bit of getting used to - I have the opposite problem. After being breast fed diesel from a very early age on a farm, I find myself constantly changing up gear to soon...
Dan J
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Chris has asked quite a difficult question as it all depends.
As Dan says ex petrol drivers tend to over rev, and equally I have known born and bred diesel atmo drivers fail to adjust to the higher revs needed with a turbo d.
It comes down to using your noddle, ie grey matter. Suss out the rev range in which the engine appears to pull well, by this I mean where the better torque is and keep it in that band. This is on the basis that the engine is working at its most efficient.
The exception to this might be when the engine is very lightly loaded, in which case I suppose highest gear in which you and the engine are comfortable is probably appropriate.
Generally the range 2000-3000 rpm is about right, though it varies from engine to engine.
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Chris P,
Perhaps more a lifestyle than just a driving style.
Travel on empty rural roads out of the main commuting times, avoid road rage overtaking for mile after mile only to end up ten cars further ahead at the town traffic lights, "drift" everywhere with something soothing like Black Sabbath on the CD.
With these carefully researched conditions a Xantia 1.9TD should be 44-48mpg.
David
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Just as a matter of academic interest, do diesel auto boxes take this torque factor into account, and change up earlier?
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The good ones do Ian. I remember years ago the magazines testing a Citroen BX Diesel Auto and finding they had got the ratios/change points spot on so that the fuel consumption was largely untouched.
David
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Thnx.
Maybe that 320d with 2 pedals ... :)
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Very Interesting!
I hadn't really thought it might be my 'driving style'; even after 15 yrs on atmo diesels, I DO still drive with the revs well up (by diesel standards, anyway).
I only get about 38 from my Focus tdi, in conditions I 'ought' to be getting c.45. No other apparent explanation, so perhaps I'll TRY a different 'style' - not easy, after all these years! I just thought I'd got a thirsty one!
Also, my advanced driving instructor had advised me to 'hang on to the lower gears a bit more', so what do you do? (And he IS a diesel driver!)
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Seems to me diesel low fuel consumption is a bit overated.Glad Lexus dont fit workmans engines.
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I agree Tony, I was standing next to a newish Toyota diesel in Saisburys as it started the other day. Thought why had they failed to match the smoothness of the diesels Peugeot/Citroen introduced nearly twenty years ago.
As for the Lexus.....Noticed a car start behind me the other day and thought how familiar the old Ford 2.8 V6 sounds, a metallic clang as the starter hits the flywheel and then a not over-smooth tickover.....turned round expcting a £300 Granada and it was a Lexus. Perhaps it sounded better inside?
David
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Trying to get petrol performance out of a diesel along with new cars extra weight can only result in poor economy , stick to the "right" size engine for the car you are considering will result in the best achivable economy , dont buy a car bigger than you need , many petrol cars get over 40 mpg so why put up with complications like turbos fitted to diesels?
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It's a funny thing Pete, we talk here of this and that connected with failures. The one thing I've never had any trouble with is a turbo. These days they are no more a complication than a brake servo.
David
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Thats good i have one on my 1.8t quattro , but still think the uncomplicated 2l primera my son now has would ultimatly be the most reliable, truble is nissan dont offer the power i wanted. A turbo petrol drives very much like a diesel plenty of torque but boring compared to the bansee of increasing revs and power
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David,
Black Sabbath takes me back a few years.....but all mine is on vinyl! Mind you my 2 year old daughter wont let us play anything other than nursery rhymes at the moment.
Ian L.
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You're missing the point. It isn't just about fuel consumption, it's the relaxed driving style that's available to you - but you're still getting along just as fast as everyone else. I'm on my first diesel and I'm sold on them.
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44-45 mpg from my Xantia HDi110 Estate - more or less regardless of how driven. I used to get 42 with my old ZX TD, so the Xantia was a bit disappointing on fuel too.
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Neil,
I've also got a Xantia HDi 110 (saloon) and get 47-48mpg. About 50% of my driving is Warwick/Cambridge/Warwick along the good old A14, mostly at about xx mph. (With light traffic, this journey (92 miles) takes me 1h15m so I'll let you work out 'xx' just in case there's a GATSO reading this). Tried experimenting recently, sticking to 70mph for the whole journey to see an expected improvement to perhaps 50+mpg. Filled up at both ends and worked it out to......47mpg!! So given my normal tankful does a good mix of town driving (which surely can only return 35-40mpg?) and I get 47-48 overall, this suggests that hammering along at 70+ returns well in excess of 50mpg!!
As for revs and pulling power (see earlier in the thread about driving style), Citroen make great play of the fact that the HDi will keep pulling into the higher rev bands. Max torque is about 1700rpm (I'm only going from memory) but pulling in 5th at these revs is much slower than kicking down to 4th and pulling thru 2500 to 3500 - it doesn't run out of oomph like the old 1.9TD did, and I feel much safer.
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I have a problem in that my two means of transport are a diesel car and a motorbike.
I find myself driving the bike more like the car, using only about half the revs I should be. It has quite good low-down torque so it's not too bad, but I find the transmission snatching in traffic due to my driving style.
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I get on average 49.5 mpg from my 2000 Vectra DI, mixed driving, say about 30% motorway. The lowest I have had is 44.5 mpg when I got it a year ago when it had 7K on the clock (Now on 25.5K). I also have a Kueberl tuning box fitted and the engine I imagine pushes out between 105 - 110hp, and 240Nm of torque. This fuel consumption is excellent, with decent performance to boot, just as good as the 125bhp 1.8 petrol but with more 'go' in higher gears.
Petrol power is becoming old fashioned and running a car is on petrol is hard to justify considering the developments in diesel powerplants.
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It does take a bit of getting used to driving a turbo diesel, but it's worth it! The combination of torque and economy are (at present) unbeatable. Mind you, my wife (SHMBO) doesn't like the sensation of catapult-like power at certain revs and has refused to drive the Audi A4 Tdi 115 again! Fair enough!
Pat
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Please could you give me a contact no for the tuners, I'd like my Di to perform as well as yours!
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Your problem could be a combination of two things. New car (tight engine will not help), and driving style.
The torque of the HDi is useable all the way upwards from 1200 RPM, and there's really no point wellying it beyond 3000. Try keeping the revs in the 1500 to 2500 band and see how that does.
Ian
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Pat's says "Mind you, my wife (SHMBO) doesn't like the sensation of catapult-like power at certain revs". When I borrowed a new A4 Tdi (130 bhp) SWMBO refused to drive it as it was slug like, slow, and downright uncouth.
Depends what you are used to I suppose. SWMBO gets 38mpg out of a hard driven A6 1.8T. This has more power than most people need at all revs not just the miniscule rev band where most turgid diesels operate.
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What GT's figures demonstrate is that if our masters are really interested in reducing the (already minor) contribution that vehicles make to greenhouse gases, then the answer is to keep them moving.
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