Is there still a valid case for diesel vs. petrol?
Discussion
I'm still trying to get my head around this, as I haven't run a diesel for about 10 years, and I haven't been doing the miles to justify it but I think my mindset re diesels is still possibly a bit out of date. 15-20 years ago, diesel seemed like a no-brainer choice if you had a substantial commute. The cost per litre of petrol/diesel was roughly the same, the diesel equivalent was 25%+ more economical, lower VED and with the advent of turbodiesels, more torque and low down power meant that the diesel was usually more drivable and quicker in "real-world" driving too, especially in a larger vehicle. And with a typical premium of only around 1,000 pounds and typically better residual values, why would you not buy a diesel?
Today with diesel being around 20p more per litre (more expensive than Super Unleaded in many cases), VED being still based on CO2 is usually still quite low but not being a company car driver, I wouldn't be able to tell you if BIK tax favours petrol or diesel. However, most modern petrol engines now have turbochargers, so match the equivalent diesel for drivability, are more refined and less complex, so more reliable? MPG of petrol cars has also improved relative to diesel over the intervening years and CO2 emissions have been lowered, so the traditional USP of diesel, namely cheaper running costs is perhaps not there any more? The biggest concern is that Euro 6 diesels are the only ones exempt from ULEZ charges and most diesels less than 5 years old are Euro 6 but for how much longer will they continue to be exempt i.e. when will Euro 7 come in and Euro 6 diesels have to pay to drive in ULEZ zones? Not such a concern with petrol, as Euro 4 and newer are still exempt from ULEZ charges, so you have a bit more leeway. It's also interesting to note that some popular models are no longer available with diesel engines and some manufacturers have abandoned diesel-engined cars completely.
On paper, using a new BMW 3-Series as an example, a 320d/330d/340d still makes a good case for itself vs. the equivalent petrol 3-Series (320i/340i etc). The 320d is actually quicker than a 320i, has a ton more torque and uses about 30% less fuel. Likewise, the 340d is as quick as the 340i has 40% more torque and uses 40% less fuel. An often overlooked benefit of the diesel is the increased range. Doesn't seem like a big deal but if you have a sizeable commute, having to fill up every other day in a lower range petrol car can be a bit of a PITA when you can commute for a whole week in a diesel. The PHEV version (330e) also brings more confusion into the mix.
I'm currently looking for an older estate car, so have the same quandary and the diesel models that I am looking at would be Euro 4/5. Not that this would affect my use too much at the moment, as I don't drive in London but if ULEZ zones expand into other cities, then that might be an issue. So would the diesel versions of this era still have an edge over the equivalent petrols for running costs or is it the same situation as with new cars? Models that I am specifically interested in are the E91 3-Series Touring, so 320i/325i/330i/320d/330d/335d and the W211 E-Class, so E320 vs. E320CDI. The diesel versions are likely to offer a bigger improvement in MPG over the equivalent petrols, lower VED and less complex, so potentially more reliable compared to their petrol equivalents?
So, does anyone have some recent insight on the diesel vs. petrol debate? Do you have both a petrol and a diesel in your household fleet and does the diesel still offer an advantage in terms of running costs? For a family i.e. non-performance car, I don't really have a preference between petrol and diesel but the relative drivability, running costs and reliability do interest me.
Today with diesel being around 20p more per litre (more expensive than Super Unleaded in many cases), VED being still based on CO2 is usually still quite low but not being a company car driver, I wouldn't be able to tell you if BIK tax favours petrol or diesel. However, most modern petrol engines now have turbochargers, so match the equivalent diesel for drivability, are more refined and less complex, so more reliable? MPG of petrol cars has also improved relative to diesel over the intervening years and CO2 emissions have been lowered, so the traditional USP of diesel, namely cheaper running costs is perhaps not there any more? The biggest concern is that Euro 6 diesels are the only ones exempt from ULEZ charges and most diesels less than 5 years old are Euro 6 but for how much longer will they continue to be exempt i.e. when will Euro 7 come in and Euro 6 diesels have to pay to drive in ULEZ zones? Not such a concern with petrol, as Euro 4 and newer are still exempt from ULEZ charges, so you have a bit more leeway. It's also interesting to note that some popular models are no longer available with diesel engines and some manufacturers have abandoned diesel-engined cars completely.
On paper, using a new BMW 3-Series as an example, a 320d/330d/340d still makes a good case for itself vs. the equivalent petrol 3-Series (320i/340i etc). The 320d is actually quicker than a 320i, has a ton more torque and uses about 30% less fuel. Likewise, the 340d is as quick as the 340i has 40% more torque and uses 40% less fuel. An often overlooked benefit of the diesel is the increased range. Doesn't seem like a big deal but if you have a sizeable commute, having to fill up every other day in a lower range petrol car can be a bit of a PITA when you can commute for a whole week in a diesel. The PHEV version (330e) also brings more confusion into the mix.
I'm currently looking for an older estate car, so have the same quandary and the diesel models that I am looking at would be Euro 4/5. Not that this would affect my use too much at the moment, as I don't drive in London but if ULEZ zones expand into other cities, then that might be an issue. So would the diesel versions of this era still have an edge over the equivalent petrols for running costs or is it the same situation as with new cars? Models that I am specifically interested in are the E91 3-Series Touring, so 320i/325i/330i/320d/330d/335d and the W211 E-Class, so E320 vs. E320CDI. The diesel versions are likely to offer a bigger improvement in MPG over the equivalent petrols, lower VED and less complex, so potentially more reliable compared to their petrol equivalents?
So, does anyone have some recent insight on the diesel vs. petrol debate? Do you have both a petrol and a diesel in your household fleet and does the diesel still offer an advantage in terms of running costs? For a family i.e. non-performance car, I don't really have a preference between petrol and diesel but the relative drivability, running costs and reliability do interest me.
Edited by white_goodman on Friday 14th October 19:28
I have a 2015 Audi A5 3.0 TDi Quattro and very happy with it. It’s the sort of car you can waft along in and I can hit 50mpg on my commute if I maintain a smooth pace. But also it has a good bit of shove when you need it. As it has a V6 engine it’s a lot smoother than a 4 cylinder and when you press on it does give out a nice roar for a Diesel engine.
I drove across northern France on the autoroutes and took full advantage of the 130kph speed limit and enjoyed accelerating up the steeper section to pass slower traffic. I thought that this would murder my fuel economy but I still got mid 40s.
I know Diesel is much higher than unleaded right now by some 20-25p per litre but with today’s prices that’s a 14% difference - not a massive margin in that context and it’s likely to be narrower again as it has been many times in the past. I did use V-power but when fuel prices shot up I began adding my own 2-EHN additive instead.
I drove across northern France on the autoroutes and took full advantage of the 130kph speed limit and enjoyed accelerating up the steeper section to pass slower traffic. I thought that this would murder my fuel economy but I still got mid 40s.
I know Diesel is much higher than unleaded right now by some 20-25p per litre but with today’s prices that’s a 14% difference - not a massive margin in that context and it’s likely to be narrower again as it has been many times in the past. I did use V-power but when fuel prices shot up I began adding my own 2-EHN additive instead.
Edited by stogbandard on Saturday 15th October 10:11
Fady said:
Thought it was as much that you seen as a leper if you still embrace diesel? What about the environment and other people's health? Not here to judge, but noted OP seems not to have factored this into the equation...
It's a fair point but has diesel just become a political "scapegoat"? I assume that Euro 6 diesels must be fairly clean or they would have to pay ULEZ charges. Is a Euro 6 diesel "cleaner" than a Euro 4/5 petrol? Less particulates I know but how clean are petrol cars in comparison, in reality? I'm all for EVs in cities, less air and noise pollution but the economic reality is that people will only adopt EVs en masse when they're affordable, it saves them money and it's not an inconvenience to them to charge etc. The vast majority of EVs currently on the market are expensive luxury SUVs for wealthy "virtue signallers", although I do applaud the likes of Peugeot/Vauxhall for offering a usable EV (e208/Corsa-e) with close to pricing parity to the petrol/diesel equivalent.For buyers of 10+ year old cars, who can't afford a new car though, the diesel vs. petrol debate is still a valid one. When you're struggling to pay your bills, a car that costs less to run is still a massive asset, even if it happens to be diesel unfortunately.
white_goodman said:
So, does anyone have some recent insight on the diesel vs. petrol debate? Do you have both a petrol and a diesel in your household fleet and does the diesel still offer an advantage in terms of running costs? For a family i.e. non-performance car, I don't really have a preference between petrol and diesel but the relative drivability, running costs and reliability do interest me.
We have a Skoda Fabia 1.2 TSi (turbo petrol), and a BMW 335d x-drive, 3 litre straight 6 twin turbo diesel.
Both are reliable, both return about the same mpg (of course diesel fuel costs more).
Too different cars to compare really. One for town, and short journeys, the other for longer journeys.
Some people (have to?) concentrate on the economics, but for me it is the torque of the diesel. It’s low down availability and its amount, that make it a joy on longer journeys, and up and down hills.
Pica-Pica said:
We have a Skoda Fabia 1.2 TSi (turbo petrol), and a
BMW 335d x-drive, 3 litre straight 6 twin turbo diesel.
Both are reliable, both return about the same mpg (of course diesel fuel costs more).
Too different cars to compare really. One for town, and short journeys, the other for longer journeys.
Some people (have to?) concentrate on the economics, but for me it is the torque of the diesel. It’s low down availability and its amount, that make it a joy on longer journeys, and up and down hills.
And that seems like a good mix. I don't think that I would have a small car diesel these days. I had a new VW Polo with the 1.4 TDI back in 2008, which was very economical and cheap to tax but it was a rough old thing. At the time, it was more appealing than the rather weak and not particularly economical 1.2/1.4 NA petrol engines being offered. There's no way I would choose it over a modern 1.0/1.2 TSI engine though.BMW 335d x-drive, 3 litre straight 6 twin turbo diesel.
Both are reliable, both return about the same mpg (of course diesel fuel costs more).
Too different cars to compare really. One for town, and short journeys, the other for longer journeys.
Some people (have to?) concentrate on the economics, but for me it is the torque of the diesel. It’s low down availability and its amount, that make it a joy on longer journeys, and up and down hills.
Likewise, the equivalent petrol (335i/340i) to your BMW would actually be pretty pleasant but I expect considerably less economical, especially when pushing on.
When I was doing business miles and getting a car allowance I ran turbo-diesels, but now I have N/A petrol 6s because I don't do enough miles to allow a DPF to regenerate.
If I still did over 14K miles a year I'd have a diesel but since my Mum passed away in 2020 I only do about 5,000 miles. so my E90 330i suits me fine.
And will be handy when the ULEZ gets expanded next year as I have family in a London Borough and it is compliant, whereas a 330d wouldn't be!
Depending on where you live, or visit, that may also be a factor.
If I still did over 14K miles a year I'd have a diesel but since my Mum passed away in 2020 I only do about 5,000 miles. so my E90 330i suits me fine.
And will be handy when the ULEZ gets expanded next year as I have family in a London Borough and it is compliant, whereas a 330d wouldn't be!
Depending on where you live, or visit, that may also be a factor.
white_goodman said:
It's a fair point but has diesel just become a political "scapegoat"? I assume that Euro 6 diesels must be fairly clean or they would have to pay ULEZ charges. Is a Euro 6 diesel "cleaner" than a Euro 4/5 petrol? Less particulates I know but how clean are petrol cars in comparison, in reality?
You've answered your own question really; diesels pre-euro ratings were dirty sooty old things. Not because it wasn't possible to make them cleaner, it just wasn't economically viable. Euro 6 wasn't the result of a technological breakthrough allowing manufacturers to finally clean things up. EFI, particulate filters and SCR are technologies that existed long before the emissions limits made them the only practicable way to pass the tests.Just like it was totally possible to build a 600bhp family estate car back in the 90s, but sales would never have covered its own development costs. These days it's viable.
Cleaner air isn't a new goal, I had a relative who died in the pea soupers of the 1950s and in the 90a I remember my parents had to get smokeless coal. Clean air is good.
In my opinion, no.
I mentioned this about a year back and got shot down. But...modern diesels, compared to NA petrol engines are considerably more unreliable with more parts that give issues and 99% of the time sound rough in 4cyl form.
Yes they have torque, but that is about the only thing going for them.
The extra few mpg is offset by the fact that diesel is now more to buy in the first place.
On a run, you would be surprised by how economical even big capacity petrol engines can be. Jaguar xk 4.2 would happily do close to 40 mpg, Volvo V70 D3 which is supposed to be a super economical car, gets 50 mpg.
I mentioned this about a year back and got shot down. But...modern diesels, compared to NA petrol engines are considerably more unreliable with more parts that give issues and 99% of the time sound rough in 4cyl form.
Yes they have torque, but that is about the only thing going for them.
The extra few mpg is offset by the fact that diesel is now more to buy in the first place.
On a run, you would be surprised by how economical even big capacity petrol engines can be. Jaguar xk 4.2 would happily do close to 40 mpg, Volvo V70 D3 which is supposed to be a super economical car, gets 50 mpg.
Do some research into the real world emissions of Euro 6 diesels.
The legal limit is 80 mg/km for NOx.
Real world tests show that in practice this is exceeded by almost a factor of 5. i.e. average output is actually 400 mg/km.
Some cars and manufacturers actually better the limit, but most are way above, and some are really bad at up to 12 times the limit.
And there are also some obvious serial offenders, including JLR.
Euro 6 is a sham and diesels need to just f
k off and die now.
The legal limit is 80 mg/km for NOx.
Real world tests show that in practice this is exceeded by almost a factor of 5. i.e. average output is actually 400 mg/km.
Some cars and manufacturers actually better the limit, but most are way above, and some are really bad at up to 12 times the limit.
And there are also some obvious serial offenders, including JLR.
Euro 6 is a sham and diesels need to just f
k off and die now.Yes get the D .
Enjoy the low down relaxing easy drive torque .
Enjoy the longer range with that less time holding a pump pistol .
Enjoy if it’s a keeper the star ship milage of reliability. 1800 rpm @70 mph as opposed to 3700 rpm
From a U.K. cost D vs P there’s nothing in it due to the as mentioned above 20 P fuel cost difference.
Buts that’s not the point otherwise walk ! Costs nothing .
But if you do a lot of mile munching in the EU where the cost difference is 10 € or less than running a D makes more sense .
Enjoy the low down relaxing easy drive torque .
Enjoy the longer range with that less time holding a pump pistol .
Enjoy if it’s a keeper the star ship milage of reliability. 1800 rpm @70 mph as opposed to 3700 rpm
From a U.K. cost D vs P there’s nothing in it due to the as mentioned above 20 P fuel cost difference.
Buts that’s not the point otherwise walk ! Costs nothing .
But if you do a lot of mile munching in the EU where the cost difference is 10 € or less than running a D makes more sense .
MattsCar said:
In my opinion, no.
I mentioned this about a year back and got shot down. But...modern diesels, compared to NA petrol engines are considerably more unreliable with more parts that give issues and 99% of the time sound rough in 4cyl form.
Yes they have torque, but that is about the only thing going for them.
The extra few mpg is offset by the fact that diesel is now more to buy in the first place.
On a run, you would be surprised by how economical even big capacity petrol engines can be. Jaguar xk 4.2 would happily do close to 40 mpg, Volvo V70 D3 which is supposed to be a super economical car, gets 50 mpg.
Out of interest, how many manufacturers still make NA petrol engines? Until recently, I have been running a large NA petrol alongside a small turbo petrol. Admittedly the large NA petrol can get close to the small turbo mpg wise on a run but in everyday use, the small turbo is significantly more economical. Likewise, diesels excel in combined/urban driving for fuel economy compared to big petrol engines.I mentioned this about a year back and got shot down. But...modern diesels, compared to NA petrol engines are considerably more unreliable with more parts that give issues and 99% of the time sound rough in 4cyl form.
Yes they have torque, but that is about the only thing going for them.
The extra few mpg is offset by the fact that diesel is now more to buy in the first place.
On a run, you would be surprised by how economical even big capacity petrol engines can be. Jaguar xk 4.2 would happily do close to 40 mpg, Volvo V70 D3 which is supposed to be a super economical car, gets 50 mpg.
Regarding NOx, I haven't looked into the figures in detail but isn't high NOx levels a byproduct of lean burn, hence why diesels typically have higher levels. Don't a lot of modern petrols use lean burn too though? Do modern, economical petrol engines pass Euro 6 NOx limits in reality?
Fiammetta said:
Yes get the D .
Enjoy the low down relaxing easy drive torque .
Enjoy the longer range with that less time holding a pump pistol .
Enjoy if it’s a keeper the star ship milage of reliability. 1800 rpm @70 mph as opposed to 3700 rpm
What the hell petrol car are you driving? Even my 1.2 Nova with its 4 speed gearbox more than 30 years ago only did 3400rpm at 70mph! Enjoy the low down relaxing easy drive torque .
Enjoy the longer range with that less time holding a pump pistol .
Enjoy if it’s a keeper the star ship milage of reliability. 1800 rpm @70 mph as opposed to 3700 rpm
And you may be spending less time holding the fuel pump, but think how sticky, slimy and smelly it is…
Deranged Rover said:
Fiammetta said:
Yes get the D .
Enjoy the low down relaxing easy drive torque .
Enjoy the longer range with that less time holding a pump pistol .
Enjoy if it’s a keeper the star ship milage of reliability. 1800 rpm @70 mph as opposed to 3700 rpm
What the hell petrol car are you driving? Even my 1.2 Nova with its 4 speed gearbox more than 30 years ago only did 3400rpm at 70mph! Enjoy the low down relaxing easy drive torque .
Enjoy the longer range with that less time holding a pump pistol .
Enjoy if it’s a keeper the star ship milage of reliability. 1800 rpm @70 mph as opposed to 3700 rpm
And you may be spending less time holding the fuel pump, but think how sticky, slimy and smelly it is…
Longer range admittedly, but my E90 330i will easily do over 400 miles on a tank.
And while it is doing less than 2,500rpm at 70mph in 6th it will happily rev to 7,000rpm, so for me it offers a bit more fun.
Just depends what you prefer really.
Difficult one.
Generally:
Petrol will be cheaper to service
Parking permits are cheaper if petrol
Residuals of petrols tend to be higher nowadays
Future price differential between diesel and petrol?
I fell foul of the diesel hype 7 years ago too, but the overtaking effort of a fully laden E320cdi at motorway speeds makes for a very relaxing drive - as does the 18gal tank.
But, £/£ I’d probably have been better off overall financially if I’d bought an older E500 at the time….
https://www.autotrader.co.uk/car-search?postcode=K...
Generally:
Petrol will be cheaper to service
Parking permits are cheaper if petrol
Residuals of petrols tend to be higher nowadays
Future price differential between diesel and petrol?
I fell foul of the diesel hype 7 years ago too, but the overtaking effort of a fully laden E320cdi at motorway speeds makes for a very relaxing drive - as does the 18gal tank.
But, £/£ I’d probably have been better off overall financially if I’d bought an older E500 at the time….
https://www.autotrader.co.uk/car-search?postcode=K...
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