Petrol vs Diesel - The Environmental Impact Of An Older Car

[DaveyBoyWonder]

Morning all. Petrol vs Diesel question with a bit of a difference (I think - I did a search!).

Our current mk5 Golf GTI daily is nearing the end of its time with us as we need something a little larger for 2 growing kids + dog. Annual mileage in the Golf is about 7/8k so not massive.

Been looking at various things, mostly 3 series tourings etc but wondered, given the annual mileage a petrol would make sense wouldn't it (lots of short journeys too). But (and this is the big one!), keep being drawn to a 330i (had one in the past and loved it). I know the economy will be pretty poor vs a diesel but given petrol is cleaner (?) than diesel, environmentally would a 330i be better than a 320D or something? Or would it be pretty even given the increased fuel consumption of a bigger petrol engine?

Is there a calculator you can work this kind of stuff out and it'll tell you?

[eybic]

Environmentally I would think the petrol is "cleaner", seemingly most diesels over 5 years old stink and chucks out plumes of smoke, this is really noticeable in traffic and I'm surprised at the age of some of the stinkers (anything out of warranty basically)

It may well be that petrol engines pollute as much as diesel but there certainly isn't a stink/ smoke cloud anywhere near as bad as diesels even from 20 year old petrols.

[NewUsername]

DaveyBoyWonder said:

Morning all. Petrol vs Diesel question with a bit of a difference (I think - I did a search!).

Our current mk5 Golf GTI daily is nearing the end of its time with us as we need something a little larger for 2 growing kids + dog. Annual mileage in the Golf is about 7/8k so not massive.

Been looking at various things, mostly 3 series tourings etc but wondered, given the annual mileage a petrol would make sense wouldn't it (lots of short journeys too). But (and this is the big one!), keep being drawn to a 330i (had one in the past and loved it). I know the economy will be pretty poor vs a diesel but given petrol is cleaner (?) than diesel, environmentally would a 330i be better than a 320D or something? Or would it be pretty even given the increased fuel consumption of a bigger petrol engine?

Is there a calculator you can work this kind of stuff out and it'll tell you?

I struggle to get less than 40mpg in a 320d doing a weeks worth of short hops only, 50 plus on long runs.

You just need to work out the mpg of a 330i, compare the running costs with the purchase and servicing prices for your mileage and roberts, your mothers brother

[Fastdruid]

It's fairly simple. Generally (as with everything there are examples that differ)

Diesel is better for CO2 and hence on the environment makes a lower impact towards global warming.
Diesel is worse for NOx and PM which kills people.

Petrol is the opposite way round.

So it really depends on which bit of the "environment" you care about.

[jackh707]

Worth a read, 3 years old but still relevant to most of us.

https://www.eea.europa.eu/publications/explaining-...

[Monkeylegend]

eybic said:

seemingly most diesels over 5 years old stink and chucks out plumes of smoke, .

Anything with a correctly functioning DPF shouldn't be doing this.

[eybic]

Monkeylegend said:

Anything with a correctly functioning DPF shouldn't be doing this.

So they say but in the real world, probably 90% of diesels (most manufacturers) over 5 years old do smell and smoke, I wonder how more cars/ vans don't fail MOTs. I'm not Diesel bashing, I drive a '19 plate Transit diesel.

[ninjag]

I can't see our Governments and Local Authorities stopping the demonisation of diesels any time soon and it's going to become more and more restrictive to drive places in an older diesel. Hell, what with Euro 6d soon to be permanent I reckon even standard Euro 6 will be attacked sooner rather than later. I also reckon that whilst petrol and diesel pump prices tend to rise and fall at similar rates, I think we'll see diesel pump prices starting to increase disproportionately to petrol.

I've got a diesel and it's Euro 5, so in a few years I'm screwed when it comes to driving into town; but thanks to rent, rates and further restricted parking etc I don't think there'll soon be much left in town to entice me anyway. I've already accepted that my car will probably be worth a pokey hat after 2022 so I'm going to run it for as long as it stays reliable, then switch to petrol and take the hit.

I've actually found that unless you are doing decent mileage on each trip then a diesel with decent performance doesn't really save you all that much in fuel, especially after taking into account higher pump prices. Where I do notice a difference is if you drive hard, a petrol definitely drains the tank much faster when you stomp on the loud pedal. But depending on the car the sound can be worth it.

[Monkeylegend]

eybic said:

Monkeylegend said:

Anything with a correctly functioning DPF shouldn't be doing this.

So they say but in the real world, probably 90% of diesels (most manufacturers) over 5 years old do smell and smoke, I wonder how more cars/ vans don't fail MOTs. I'm not Diesel bashing, I drive a '19 plate Transit diesel.

I don't see that where i live and drive, you very rarely now see plumes of black soot being pumped out on acceleration as you did pre DPF.

Mine is 9 years old nearly and 312k miles and no smoke.

Petrol cars smell and smoke as well

[ninjag]

Monkeylegend said:

eybic said:

seemingly most diesels over 5 years old stink and chucks out plumes of smoke, .

Anything with a correctly functioning DPF shouldn't be doing this.

My Euro 5 has a very efficient DPF, but you can smell the tail pipes when stationary. No black smoke though. The smell isn't over powering, no more than say what you would smell from a petrol (but a different smell of course). Compared to a proper Euro 6 where you can smell almost nothing there's definitely a difference, I say proper because I've walked past VW, French and Vauxhall cars which are supposed to be Euro 6 and they stink.

[Fastdruid]

Monkeylegend said:

Petrol cars smell and smoke as well

It's vanishingly rare though.

Older carb cars utterly stink, older carb bikes less so but still noticeable.

Very, very occasionally there will be an oil-burning petrol car but it's once in a blue moon.

Stinky and smoky diesels OTOH are a daily occurrence.

[Dave Hedgehog]

Fastdruid said:

Monkeylegend said:

Petrol cars smell and smoke as well

It's vanishingly rare though.

Older carb cars utterly stink, older carb bikes less so but still noticeable.

Very, very occasionally there will be an oil-burning petrol car but it's once in a blue moon.

Stinky and smoky diesels OTOH are a daily occurrence.

problem is diesels have very complex and expensive systems on them to try and control the tail pipe emissions, as they get older some owners just remove the system rather than repair it (DPF delete etc.)

[Monkeylegend]

Dave Hedgehog said:

Fastdruid said:

Monkeylegend said:

Petrol cars smell and smoke as well

It's vanishingly rare though.

Older carb cars utterly stink, older carb bikes less so but still noticeable.

Very, very occasionally there will be an oil-burning petrol car but it's once in a blue moon.

Stinky and smoky diesels OTOH are a daily occurrence.

problem is diesels have very complex and expensive systems on them to try and control the tail pipe emissions, as they get older some owners just remove the system rather than repair it (DPF delete etc.)

Yes, I should have added and correctly maintained.

[ninjag]

Monkeylegend said:

Dave Hedgehog said:

Fastdruid said:

Monkeylegend said:

Petrol cars smell and smoke as well

It's vanishingly rare though.

Older carb cars utterly stink, older carb bikes less so but still noticeable.

Very, very occasionally there will be an oil-burning petrol car but it's once in a blue moon.

Stinky and smoky diesels OTOH are a daily occurrence.

problem is diesels have very complex and expensive systems on them to try and control the tail pipe emissions, as they get older some owners just remove the system rather than repair it (DPF delete etc.)

Yes, I should have added and correctly maintained.

I think a lot can be said for this. I do oil changes with a decent brand C1 oil every 6 months (Millers, Fuchs etc), I only ever put BP Ultimate diesel in my car and a can of Archoil AR-6400d Max goes in every 5,000 miles as well. I've been monitoring my soot levels and the DPF is clearing it passively with a reasonably short motorway drive so it's working well. As for those who do a DPF delete, what happens if they are in a crash and it's discovered, would the insurance company not latch onto this to void the policy?

[ZeroGroundZero]

Fastdruid said:

It's fairly simple. Generally (as with everything there are examples that differ)

Diesel is better for CO2 and hence on the environment makes a lower impact towards global warming.
Diesel is worse for NOx and PM which kills people.

Petrol is the opposite way round.

So it really depends on which bit of the "environment" you care about.

Not one for signing up to the global warming bandwagon, I would say the choice is petrol if having any care for the environment.
Opt for petrol, kill fewer people and at the same time produce the critical gas that plants/crops strive on
(joking of course - quite new to PH so hopefully not taken the wrong way)

[ZX10R NIN]

At 7-8k a year you should be buying a petrol, there really isn't a petrol vs diesel debate to be had with your annual mileage.

You should by the drivetrain that's the most efficient for your usage, all forms have an impact on the environment it's just dependent on what bit of the environment you care about, also your budget will dictate how environmentally responsible you are.

Remember the biggest producer of NOX gasses are household boilers, so you night want to change that first, cars are a small part of the air quality equation & it's improving because on average people upgrade every 4 years in the UK.

[S100HP]

Monkeylegend said:

eybic said:

Monkeylegend said:

Anything with a correctly functioning DPF shouldn't be doing this.

So they say but in the real world, probably 90% of diesels (most manufacturers) over 5 years old do smell and smoke, I wonder how more cars/ vans don't fail MOTs. I'm not Diesel bashing, I drive a '19 plate Transit diesel.

I don't see that where i live and drive, you very rarely now see plumes of black soot being pumped out on acceleration as you did pre DPF.

Mine is 9 years old nearly and 312k miles and no smoke.

Petrol cars smell and smoke as well

I agree. I just don't see 90% of diesel cars pumping out black soot. I see it very ocasionally.

My XC70 is nearing 160k and no soot.

[DaveyBoyWonder]

Thanks everyone - definitely food for thought. I was erring towards petrol anyway but this has pretty much confirmed it especially with my annual mileage.

[pyruse]

I often see clouds of black smoke coming out of the back of diesel cars, some of them not that old. Saw a 6 year old Audi the other day which put out a huge cloud of smoke every time he accelerated. I don't know what percentage of diesel cars are like that, but probably about 10%. Of course builders' vans and trucks always seem to belch out black soot. How do these vehicles pass MOTs?

[ninjag]

pyruse said:

I often see clouds of black smoke coming out of the back of diesel cars, some of them not that old. Saw a 6 year old Audi the other day which put out a huge cloud of smoke every time he accelerated. I don't know what percentage of diesel cars are like that, but probably about 10%. Of course builders' vans and trucks always seem to belch out black soot. How do these vehicles pass MOTs?

Friendly MOT garage, can't think how else because some of the black death coming out of vans is awful. Same for some buses, I see it and whack on the recirc straight away.

I wonder about some cars which aren't all that older yet belch out the black death, could it possibly be due to a bad or overdone remap or budget tuning box?