In the third part of our Fuel series, we look at diesel.
Are diesel cars more fuel-efficient?
As price-pressured motorists look to get more bang from their buck, sales of diesel light vehicles have increased rapidly over the last couple of years. Due to lower fuel consumption rates than an equivalent petrol engine, diesel engines are the standard in heavy vehicles. So why not in light engines too?
Pros:
- Modern diesel engines are as quiet, smooth and powerful as petrol engines and are more fuel-efficient.
Cons:
- One disadvantage often mentioned by NRMA Members is that diesel handpieces at garages often have a film of diesel fuel over them, as any spillage does not evaporate as quickly as petrol. And if the diesel gets on your hands or clothing, the smell is difficult to remove. Retailers are making efforts to avoid this but have not yet found a perfect system.
Consider:
- Diesel fuel does not contain more energy than petrol. In fact, it contains marginally less.
- Whereas the intake of a petrol engine has a throttle blade in it, which forms an obstruction and reduces efficiency, a diesel engine doesn’t. Therefore, it gets lower fuel consumption.
- Diesel variants are often more expensive to purchase than the petrol ones, so if your interest is purely in lower running costs, make sure it is going to make sense for you by checking out the NRMA’s Car Operating Cost Calculator.
- In many cases, the higher initial purchase cost outweighs the reduced fuel cost. But you are also gambling on the price of diesel staying similar to petrol over several years.
- If you have never driven a diesel-engined vehicle and are considering purchasing one, you should test drive a few to see how it feels.
If you drive a diesel car, do you feel you’ve you got your money back in reduced fuel/servicing costs? And are you happy with the driving characteristics of diesel?
I am on my second turbo diesel car in four years (Mazda6 Diesel Wagon) and have bought two now for the drive-ability factor alone, lots of torque at low revs, you don’t need to rev the engine to get power, easy overtaking and charging up hills.
I love them.
Towed a caravan with my XR6 BA Falcon and got terrible mileage (19l/100kms). ‘Upgraded’ to a 2010 Nissan Navara D40 2.5 Turbo diesel and mileage went to 22ltrs/100kms!! Local Nissan Dealer says all is well. Not likely, still looking for answers. Efficiency should be MUCH better with the Nissan.
We bought a Series 2 LX Captiva Diesel just over a month ago, so far I am really loving it I do like the way it drives. The Diesel has plenty of torque for going up even the steepest hills without a problem. The sportshift function in the transmisson makes this easier as well. I thought I was going to regret buying it after a month as I had traded in an SS Commodore for it but I’m loving it more and more everytime I drive. Certainly doesn’t have the outright power and acceleration of my old SS but it more then makes up for it for being more user friendly.
The Diesel was only $1000 more then the petrol version which we didn’t like and I’ve been told is not as good on fuel as the Diesel.
So far I’ve saved $120 in petrol compared to my old car so I’m really happy indeed.
Only need to have Captiva Serviced once a year and the costs I’ve been told are close to $300 or a little bit more.
My old car by comparison was every 6months and between $350 or $450 sometimes abit more so I’m saving money again there.
We bought a Series 2 LX Captiva Diesel just over a month ago, so far I am really loving it I do like the way it drives. The Diesel has plenty of torque for going up even the steepest hills without a problem. The sportshift function in the transmisson makes this easier as well. I thought I was going to regret buying it after a month as I had traded in an SS Commodore for it but I’m loving it more and more everytime I drive. Certainly doesn’t have the outright power and acceleration of my old SS but it more then makes up for it for being more user friendly.
The Diesel was only $1000 more then the petrol version which we didn’t like and I’ve been told is not as good on fuel as the Diesel.
So far I’ve saved $120 in petrol compared to my old car so I’m really happy indeed.
Only need to have Captiva Serviced once a year and the costs I’ve been told are close to $300 or a little bit more.
My old car by comparison was every 6months and between $350 or $450 sometimes abit more so I’m saving money again there.
I primarily purchased a diesel vehicle in 2003 for long distance touring due to availability of diesel in remote areas. At the time petrol sniffing was rife and talk was of removing petrol from remote locations, forcing my hand. The price differential between petrol and diesel has been most disappointing over the period, and yes, there are some regrets. I have not found reduced servicing costs at all.
The diesel is no longer used to commute, I am back to state rail while diesel per litre cost remains so far above unleaded.
I have owned a Citroen C5 2.0 Turbo diesel Wagon for more than three years now. It replaced a 3L Petrol C5 in which I did almost 200,000 Klms.
The diesel is more powerful, heaps more economical, and trouble free. I love it for effortless smooth driving, particularly with its 6 speed auto.
I cant wait to be in a position to buy the next generation of C5 diesels.
I recently had a test drive in a VW Tig. 103 tdi diesel powered SUV. Its performance staggered me. I could not believe a mid sized diesel car could be such fun to drive and when the time comes to change over a`diesel powered car would have to be seriously considered.
I had not driven a diesel powered car for some 20 years so it was a real revelation to find out how time has changed their performance. My current car since new is a Commodore ’97 VT Berlina. My two previous vehicles were Ford Fairlanes so I feel I can make a reasonable comment on some of the changes that have occured over the years.
Of interest to our younger members I lived at Lane Cove for a couple of years back in 1956/58 and remembered that a small four door four cylinder Mercedes taxi used to be in use there during that time. Its the only diesel taxi I ever saw in Sydney at that time. I often wonder what happened to it and its history. It would make interesting reading
One final comment….Look at the cost of servicing at about 60,000klm. They can be more expensive than the petrol equivalent.
I purchased a peugeot 307 diesel wagon 3 years ago replacing a magna wagon. Performance is much better than the magna even though the engine is smaller. Diesel is more expensive and messier than petrol but the 1000km range means you spend less time queueing at petrol stations. Servicing is a bit more. Overall a great engine which makes the car easier to drive.
I’m very happy with my Skoda Octavia TDI. It took a little adjusting getting used it being more sluggish off the mark turning onto streets in city traffic, but now I don’t think about it, and once up and moving the performance is comparable to the Mazda 6 I had previously. I get about 6.5 L/100km in real world driving, which is excellent.
The issue of dirty handpieces at the pumps is a real one. I carry a pack of disposable gloves in the car to use when refuelling. Not having to refuel so often more than makes up for this inconvenience.
I purchased a Hyundai Santa Fe diesel wagon 2 years ago replacing a mazda MPV wagon. Performance is much better than the mazda even though the engine is smaller abot 2 ltrs. Diesel is generally more expensive than petrol but the increase in km range means you spend less time at petrol stations and I consistantly have done a comfortable run from the Broadwater end of the Gold Coast to home in Newcastle on approx 75% of a tank compared with at least two fills on my 2.6 ltr petrol MPV. Servicing is a bit more expensive. Overall a great engine which makes the car easier to drive for myself and my family members.
I recently bought a second-hand ’07 Prado auto diesel. Its D-4D engine has a service interval of 10,000km (up from 5,000km on previous Toyota diesels). On a recent 3500km trip it averaged 9.4l/100 whilst cruising at highway speeds. With its 180litre tank capacity I can usually choose to refuel when I find “cheap” fuel (brand name only thanks!). The Prado is a quiet cruiser though there is some engine noise on acceleration, very much like a Golf diesel.
The smelly diesel handpieces can be a nuisance but then refuelling doesn’t occur often and the bigger servos have washrooms.
As for service costs: the 10,000km service interval is the same as for a petrol engine and no electrical items (plugs, leads, etc) ever need replacing.
In the future I would definitely buy another diesel.
Diesel Cruze, used only in Sydney traffic. Claimed mileage inaccurate, closer to 10 L/100 km, in off-peak traffic. Mind-numbing torque at low speed. Noisy engine is a put-off, but not increased with heavy loads. Not limo material. Harder on batteries. Freezing weather could present starting problems. Use only branded fuel to avoid water damage, and engine oil suited specifically to particulate filters, otherwise PC can be damaged. The unschedule 25 min non-stop driving particulate filter regeneration cycle is a clumsy afterthought, with high heat and smell levels. Turbo and high compression makes acceleration and steady driving difficult to control, often requiring downhill acceleration, or engine run-on when the gas pedal is off. No accelerator response when turning into side streets, with turbo Freezing weather could present starting problems.off-boost. Pricey and messy at the pump. Washing doesn’t remove fuel smell. Long waits between fills are a redeeming convenience. Longer service periods are result of bigger oil capacities, and hence higher service cost. Still not emissions clean. Slow response from local fuel refiners.
The greater efficiency of a diesel engine occurs because the fuel is ignited at a higher temperature than in petrol engines.
The presence of a throttle blade in the intake is not relevant.
I’ve had a Discovery diesel for 18 years and I am very happy with it.
Yes and no! I agree that dot point 2 of the article is incorrect. There are a myriad of factors that influence efficiency of an internal combustion engine. The most fundamental factor is compression ratio. The higher the compression ratio, the higher the efficiency. Diesels generally have a higher compression ratio that petrol engines. More importantly, petrol engines achieve maximum compression only when the throttle is wide open which occurs infrequently, whereas diesel engines, with not throttle at all, are always wide open and always run at maximum compression. So while the diesel is still more efficient at highway speeds, its greatest advantage is at lower speeds.
The absence of a throttle reducing throttle restriction is a furphy. Yes it is true but the effect is minor.
One disadvantage of always running with effectively a wide open throttle, is that the engine always draws maximum air per rev. Thus induction noise is higher, filter air flow head loss is greater and the filter clogs quicker.
Just purchased our first Diesel, a HOLDEN CRUZE six speed auto, pure magic 60 liter tank range 800 plus kilometers as against our trusty 1992 petrol HOLDEN VP Station wagon 640 kilometers from 64 liters. NUF SED
Last year I went from a diesel car (SsangYong Rexton 2.7 auto) to petrol (Renault Koleos Privilege 2.5 CVT auto) and was initially disappointed with the economy from the smaller SUV, having averaged 10.8 l/100km (corrected for the ever-present speedo/odometer error) over 80,000km in the Rexton. I found 91 octane fuel actually gave better economy than 95 (which, strangely, is recommended for the Renault despite the same engine in X-Trail being rated at 91 octane). However, I had a pleasant surprise at the Koleos’ first service, 10,000km- it was under $200, at the local Nissan dealer! The cheapest 10,000km interval service on the Rexton was $250, the dearest, $1250! Combined with the lower cost of petrol (at times lately, diesel is 12cpl dearer in my town), the running costs on the Koleos are much cheaper. I don’t know what a diesel Koleos would cost to service, and the interval is 15,000km, but diesel wasn’t available in Privilege grade in any case. I don’t have to put up with dirty, slippery forecourts, smelly nozzles, and a complaining wife (from the smell on my hands) after I fill up, but I still miss the torque and “feel” of the diesel.
‘We’ve had petrol, gas and diesel vehicles (mainly 4 wheel drives) over the past 40 years. My wife’s diesel Peugot 306 is 11 years old, still reliable and economic and goes like a sports car. My previous diesel was aNissan Torano two, gave 10 years service and I always considered it the sports car of 4WD’S. My current car is an automatic turbo diesel Hyundai I30 and is not only economic but a pleasure to drive. Need I say more.
I purchased a 21st anniversary Mitsubishi Pajero DiD new in 2004. I am extremely happy with this vehicle and have definately recouped the additional $1400 which I paid for the diesel motor. Fuel consumption has averaged less than 10litres per 100klms which includes towing a 2tonne caravan where fuel consumption has risen to 16.5litres per 100klms. Service intervals are 15000klms, however I choose to service every 7500klms and only ever use top quality Penrite HPR oil. As for diesel service costs being dearer than petrol service costs, I believe they are justified by the much better fuel consumption and towing abilities. My wife also loves the “purr” of the motor as we lope along.
I purchased a 21st anniversary Mitsubishi Pajero DiD new in 2004. I am extremely happy with this vehicle and have definately recouped the additional $1400 which I paid for the diesel motor. Fuel consumption has averaged less than 10litres per 100klms which includes towing a 2tonne caravan where fuel consumption has risen to 16.5litres per 100klms. Service intervals are 15000klms, however I choose to service every 7500klms and only ever use top quality Penrite HPR oil. As for diesel service costs being dearer than petrol service costs, I believe they are justified by the much better fuel consumption and towing abilities. My wife also loves the “purr” of the motor as we lope along. I would certainly recommend a diesel and will replace the Pajero with another diesel when ready to purchase another vehicle.
Purchased a Ford Focus Diesel with new 6spd powershift transmission 15 months ago. Vehicle is for business and does a mainly urban with some regional travel. After 40,000 Km average fuel consumption was 6.3 ltrs/100km overall. 2 x services @ 15K intervals @ $350. Best result was Sydney to Brisbane on one tank ie 827Km for 42.1 ltrs or 5.1 ltrs /100km. Lots of torque make it a pleasure to drive. Extra cost of diesel variant has already been recovered in fuel savings and lower maintenance costs. This is my first diesel. Now looking at a VW Polo diesel for my wife.
P.S. I carry a cheap cotton gardening glove to keep the smelly stuff off my hand. Have also used the paper towel provided by the servo to cover the handle.
It’s all down to maths: if you know how far you drive annually, it’s pretty easy to work out when the better fuel economy will repay the higher purchase price. For us, depending on fuel prices, we’ll get ahead in the second year. And, as Graham said, modern diesels are a revelation if you remember the diesels of old. It will depend on what you’re looking at, but the diesels are the pick of several model ranges.
Switched to a Peugeot 308 2.0 HDi wagon back in Nov-11 specifically for lower mileage.. currently getting about 7.7L/100km from Sydney driving – mainly between Liverpool and Chatswood.
Diesel price can often be cheaper than, if not comparable to, Premium Unleaded (95 RON), which is what my other vehicle choices would’ve demanded anyway.
Our other car, a 2006 Forester 2.5 XT Luxury, is averaging 13L/100km; thinking of replacing it with another diesel.. the new Territory diesel maybe.
The slimy handpiece is definitely a real issue. In Europe where diesel passenger vehicle use is more prevalent, the garages have cheap plastic gloves to deal with this. Over here, I grab a generous amount of garage-supplied paper towels to wrap around the handpiece – I learned very early on never to handle a diesel handpiece directly. Thanks go to Paul for the good idea of having a box of disposable gloves in the car.
I drive a Golf 2.0 TDI and love it. I especially love getting 1,000km+ per tank. The pulling power is best served when on cruise control as the car just sits on the selected speed without varying. I will only change from diesel when an affordable EV is available.
I purchased a 2.5 lt Kia Sorento mainly for towing purposes. I find the diesel far more tractable both towing and around town. As for fuel consumption 30000 km around Oz in 12 months towing a two and half tonne caravan, avg fuel consumption for the trip 13.5 lt per 100km. On trips from Port Macquarie to Sydney avg is 9.5lt per 100km. Engine torque is such that there is only one hill in the whole trip where the car changes from 5th to 4th while in cruise control. Always carry a pair of leather gloves in the back and the bowser handpiece is never a problem. $15 will get a good pair of soft hide ones.
Apart from greed from the petrol companies. Why are we paying so much for fuel at the petrol station? It’s been around the $85 a barrel mark for some time and yet we are paying more per litre than when it was more expensive
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G/DAY,
If i get 10.60km per litre of diesel in my ute how many litres per 100 kms is this and how do i work out litres per 100kms.
Hi John
Divide your km/L figure into 100 to get L/100 km – so yours is around 9.4 L/100 km.
Cheers
Jack
hi is it normal for a sante fe high lander turbo diesel auto 2011 to be getting around just over 10 ks to the litre in the city or is it to high
Hi Barry and Narelle
Your fuel consumption of 10 litres per kilometre equates to 10 litres/100kms.
The indicated fuel consumption to ADR (Australian Design Rules),as harmonised with the ECE (European Rules), for a MY11 Santa Fe is 7.5 litres/100km.
The ECE tests are for comparative purposes only tested under laboratory conditions, and as such it is likely the actual consumption under practical driving conditions would be higher. Therefore 10 litres/ 100 kilometres is not outside the expected range.
Cheers
Jack
Hi,
I looked up the ADR figures for the Sante Fe Diesel.
It is 7.5l/100km combined & 9.4l/100km for urban driving.
So if you are getting around 10.6km/l around the city you are spot on the adr figures for urban driving.
(100km divided by 9.4l/100km = 10.6km/l)
Based on the ADR figures you may get 13.33km/l for country driving.
I hope that helps,
Regards,
David.
I agree. The ADR fuel standards are fake. They are based on impossible standards. I cannot understand how ADR fuel reports can be display on vehicles when its impossible for that standard vehicle to obtain the same economy figures on road. Its deceiving and wrong.
Have owned 2007 Mazda 6 MZR-CD 2 litre diesel since Aug 2008 and done 100,000 km at average 6.7 litres per 100km. This includes a lot of city driving but still equates to more than 42 mpg (yes I am over 50). At time of purchase comparison costs to previous 3 litre petrol car (1986 Nissan Skyline) was $12.50 per per hundred ks petrol versus $9.80 per 100 ks diesel based on average prices in first month of ownership – and this ratio still holds up today. I live in Canberra and diesel ranges from being 12-15 cents more expensive than petrol to being a few cents cheaper than e10 at the Coles/Woolworth branded thieving stations. Service costs are higher – but careful shopping around can find some dealers cheaper than others – especially in western Sydney. Have only had one mechanical issue, the DPF clogged (at 102,000 kms) which was fixed by recalibrating the injectors. I also learnt to modify driving habits to aid burn off – i.e. take a long fast drive once a week – normally at 100 kph in fourth gear for 20+ ks
I have a new Cruze CDX diesel. I am lucky to get 10ltr/100km in off peak driving and am particularly surprised and annoyed that this car performs more poorly than a Toyota Corolla in this respect. Add to that the random running of the fan at full speed after engine shutdown for whatever reason, a flat spot that occurs randomly under acceleration, and an inability for the dealer to do anything about it, makes one convinced never to buy one of these again. I dont get why Holden have chosen the roughest, noisiest, most thristy old diesel they could find to stuff into this car. I should not really be surpised insofar as they still seem to be recycling the old 1.8 ecotech motor in other models of theirs. I wish there was a fix for the poor economy of this thing – new software, anything. It defeats the purpose of the diesel
I have a Triton GLXR.
First diesel of my own and LOVE IT!!.
More touque than an tuppaware festival. Smooth and reliable.
Big disapointment that some valvle on the fuel pump was relaced at 5yrs 1 month. They tell me teh extra 5 year “drive train ‘warranty does not cover parts of the engine.
Really cross that the price of diesel has gone up so high. Why was it cheaper than ULP until the NRMA did a big story on motorists changing to diesels? The fuel costs less to refine but we pay more at the bowser??
Still I average 11L/100 around town in a 3 tonne so thats not too bad. About the same cruising at 110 on the highway too.
I love diessel engines, however I am unable to find out how to drive a modern diessel engine correctly. The holden cruze manual does not talk about it at all, the mechanics in holden services are useless and only offer their uneducated oppinion and holden itselfs reffers you back to those mechanics.
It apears to me that those engines had been designed by aliens who left the planet and did not leave instructions behind.
Many different opinions is on the internet, some of them seem to be good , other other totaly useless.
Can anyone reffer me to a reputable site or a place which understands fully the function of a modern diessel engine?
The deers information is very conicting. such as recomendation to drive at high revs. 1/ whT is it high revs? 2/ even if it is just over 1800 rpm that would mean that most drivind would have to be done at third gear. some driving on 4th and fiftf gear only on Freeways. 6th gear would be ilegal as at 110 km/ h you rev barelly 1500RPM. I understand thT most people just want to drive, but I do like to drive it at its best. Any help would be apreciated.thanks
couple more things. 1/ I did have issue with surging and the dealers were very reluctant to deal with it. Badicly they had no idea and came up all different bulshit stories, which were mostly hard to swalow even for my 67 years old mother. However after a complait to fair trading and 2 weeks without the car, it had been fixed and I am getting well below 6 litres / 100 km in light city trafic. There still is a little glitch which I intend to have rectified by at least I am getting close to what I expected from a diesel engine.
Hi all,
I recently test drove the Ford Focus 2012 deisel MK2 Sport and loved it. I will only be doing around 15,000 km a year mainly in around the city. I’ve been reading the DPF can get clogged up if only doing city driving as the engine does not get hot enough to burn off the soot, however I have also read if you do a 20 min drive above 2000 rpm once a week out on the highway to get the engine hot enough, this will clear the DPF?
Any comments about the above or about the Ford Focus diesel would be much appreciated
Luke
Hi Luke
DPFs are designed to be self-cleaning. When the system detects it is getting clogged, it increases the fuel rate slightly which raises the temperature of the filter, causing the soot to burn off. If you do a lot of motorway driving, the temperature will normally get high enough in normal operation to burn off the soot, so this function will not operate.
Cheers
Jack
I drive a Citoen C5 2.2 HDI, I am getting 960km per tank for local running and around 1100 on long runs.
I’ve a 4-year old Citroen C4 diesel. Very happy with performance and with consumption: 4.4 to 5.5 L/100 km. I’m not happy with the premium price for diesel fuel; it should be cheaper, with less refining (?). And better for the environment (?). NRMA should press the oil companies. Diesel usage should be increasing percentage wise (?) We diesel users are not all company truck drivers!!
I have a 2008 GU Nissan Patrol. The fuel economy sticker when purchased showed 10.9l/100km city. However I have now been told this is impossible to get in a normal road vehicle. This rate is apparently under specific test conditions when the vehicle is emptied of seats and other weight. I am lucky to get 13.9l/100km average city or highway.
Such information is misleading to purchases and should be stopped. I complained to Nissan because they use this information when selling vehicles but they just say this is a government provided statistic to which they are not responsible for.
Hi Peter
Vehicle manufacturers submit their fuel consumption figures to the Federal Government and they are published on the Green Vehicle Guide website http://www.greenvehicleguide.gov.au/. The figures come from the same driving cycle as the emission test results which the manufacturers have to perform to show the vehicles comply with emission standards. The tests are performed in a laboratory on a rolling road so conditions are standardised and there is a specified test weight to simulate passengers and luggage. The cycle is mostly low speed so if your normal driving mode is different you will have different fuel consumption. Also manufacturers will always try to get the best possible figures which may not be achievable on the road. However the GVG figures are useful as a comparison between vehicles as it is a standardised test. Many vehicles do achieve their stated fuel consumption when driven carefully. The figures for the diesel Patrol are 9.2 L/100km highway and 14.1 urban, so you have to apportion your driving distance.
Cheers
Jack
What is the difference between diesel fuel for cars and heavy vehicles?
dot point 1 is factually incorrect; diesel most certainly does contain more energy per litre than petrol ~ 39Mj/L against ~35Mj/L for petrol
Hi Peter, I bought a (demo) new VW POLO Diesel Automatic going on 4 years ago. I mainly do short trips all week, school run etc and the salesman knew this. I am SO UNHAPPY with this car and I want other people to know about the stupid particulate filter. This filter blocks at least once a tank of fuel and I am then required to ‘drop everything’ and drive for 40 minutes without stopping. Which means no matter where I am I feel I have to go, middle of the night, on the way to appointments and so on. I just have to wonder why NO ONE mentions this filter when selling the car??? And it seems this car is marketed as a good one for city driving – I just don’t believe that. I wish I could give the car back, I does my head in!!!
oh sorry! That was meant to be ‘Jack’!
Hi Elizabeth
Have you had this checked out by VW? If you are using one specific servo to fill up, try changing brands to make sure it isn’t one particular fuel source that is causing the issue. Let us know how you go.
Cheers
Jack
hi Jack, yes I have. The first time i had it happen was a few weeks after purchase. I was near to the place where I bought it and the mechanics were there. The guy told me that, that’s how it goes, he suggested I headed for the freeway (f3) down to the Toronto exit – about a 20 minute run each way. I was floored!! and is said’ your’e joking – right?’. I have since done quite a bit of research and found that i’m not alone, this car is not meant for city driving at all and yet it’s marketed like it is. I will give the different fuel a go but I don’t really stick to one i have three that i rotate about.
The second time I had it happen i didn’t do the run till about a day later, whoa and behold the thing went into limp mode and i had to get towed to the workshop where they had to ‘manually’ clear the filter or so i was told. They had the car for a week. Since then I never put it off but it is such an intrusion into my life.
My goal here i guess is to let other people know because had i known there is NO WAY I would have bought this car of the year!!! cheers
I have had a 1995 toyota surf 3ltr diesel for just over 12 years now and still love it only once has it let me down about a year ago needed a new fuel pump we have driven to darwin and right down the west coast stopping in the kimberley and doing a lot of off road driving. Across to to Sa then Vic and on to Sydney then home to the blue mountains. I cannot praise this car enough I have read so many bad reports on the Surf.My wife wants to know when im trading in but if its not broke why fix it