Pump price of diesel relative to petrol

[NY]

I'm old enough to remember when diesel was about half the price of
petrol, back in the days when only taxis and a few Mercedes cars (and
obviously lorries) used it.

That changed when the fuel duty of diesel was raised to the same amount
as for petrol.

But even then, diesel was usually a few pence per litre cheaper than
petrol. It has steadily increased (relative to petrol) since then, and
has been a few pence more than petrol for a long time. The difference
has increased dramatically as a result of the recent silly season for
fuel prices, but I imagine the disparity will gradually lessen as prices
start to return to their previous level.

But what governs the cost of diesel relative to petrol? Is the cost of
production more, less or the same for both? Is diesel more expensive
because less is made, as people change back to petrol cars (eg
petrol-electric hybrids)? Does the price vary depending on the time of
year, because more central heating oil is made in winter, and diesel and
CH oil are a similar fraction of crude oil? Does a unit volume of crude
oil yield roughly the same amount of petrol and diesel?

I wonder how long it will be before a diesel car is actually more
expensive to run than a petrol one, because the extra per-litre cost of
the fuel outweighs the much better mpg of diesel.

[Recliner]

Post by NY
I'm old enough to remember when diesel was about half the price of
petrol, back in the days when only taxis and a few Mercedes cars (and
obviously lorries) used it.
That changed when the fuel duty of diesel was raised to the same amount
as for petrol.
But even then, diesel was usually a few pence per litre cheaper than
petrol. It has steadily increased (relative to petrol) since then, and
has been a few pence more than petrol for a long time. The difference
has increased dramatically as a result of the recent silly season for
fuel prices, but I imagine the disparity will gradually lessen as prices
start to return to their previous level.
But what governs the cost of diesel relative to petrol? Is the cost of
production more, less or the same for both? Is diesel more expensive
because less is made, as people change back to petrol cars (eg
petrol-electric hybrids)? Does the price vary depending on the time of
year, because more central heating oil is made in winter, and diesel and
CH oil are a similar fraction of crude oil? Does a unit volume of crude
oil yield roughly the same amount of petrol and diesel?
I wonder how long it will be before a diesel car is actually more
expensive to run than a petrol one, because the extra per-litre cost of
the fuel outweighs the much better mpg of diesel.

I think the proportions of petrol to diesel depend on the types of crude
oil being refined, and the refinery settings. It's a world market, so
fluctuating UK demand won't influence prices very much. I believe we used
to have significant diesel imports from Russia; banning those will have
raised the price of diesel.

[NY]

Post by Recliner
I think the proportions of petrol to diesel depend on the types of crude
oil being refined, and the refinery settings. It's a world market, so
fluctuating UK demand won't influence prices very much. I believe we used
to have significant diesel imports from Russia; banning those will have
raised the price of diesel.

Ah, so some fuel sold in this country comes from refineries outside the UK?
I hadn't realised that.

[Recliner]

Post by NY

Post by Recliner
I think the proportions of petrol to diesel depend on the types of crude
oil being refined, and the refinery settings. It's a world market, so
fluctuating UK demand won't influence prices very much. I believe we used
to have significant diesel imports from Russia; banning those will have
raised the price of diesel.

Ah, so some fuel sold in this country comes from refineries outside the UK?
I hadn't realised that.

<https://news.sky.com/story/uk-has-imported-220-million-of-russian-oil-since-ukraine-war-outbreak-analysis-suggests-12599462>

[JNugent]

Post by NY
I'm old enough to remember when diesel was about half the price of
petrol, back in the days when only taxis and a few Mercedes cars (and
obviously lorries) used it.
That changed when the fuel duty of diesel was raised to the same amount
as for petrol.
But even then, diesel was usually a few pence per litre cheaper than
petrol. It has steadily increased (relative to petrol) since then, and
has been a few pence more than petrol for a long time. The difference
has increased dramatically as a result of the recent silly season for
fuel prices, but I imagine the disparity will gradually lessen as prices
start to return to their previous level.
But what governs the cost of diesel relative to petrol? Is the cost of
production more, less or the same for both? Is diesel more expensive
because less is made, as people change back to petrol cars (eg
petrol-electric hybrids)? Does the price vary depending on the time of
year, because more central heating oil is made in winter, and diesel and
CH oil are a similar fraction of crude oil? Does a unit volume of crude
oil yield roughly the same amount of petrol and diesel?
I wonder how long it will be before a diesel car is actually more
expensive to run than a petrol one, because the extra per-litre cost of
the fuel outweighs the much better mpg of diesel.

A given quantity of crude oil contains more of the makings of diesel
than it does of the requisite components of petrol, so there really
isn't a good reason for diesel to be more expensive based on alleged
scarcity.

It must have something to do with the much greater use of diesel in cars
and light vans as compared with, say, fifty years ago and the greater
demand for the fuel.

A friend then had a diesel-powered Transit van (itself not without
problems, since the more primitive injection systems of the day were
more intolerant to low tank levels and could easily develop an injector
air-lock), but diesel was about 32p a gallon while petrol was 36p a gallon.

I got my first diesel car - a new Citroen Visa 17D - in late 1986, and
kept it until 1992. That was unheard of at that time. I'd never kept a
(petrol) car that long because something always went wrong with them.
But diesels are inherently hardy, reliable and trouble-free. My current
(diesel) car, new in early 2014, shows not a single problem (touch wood)
eight-and-a-half years later.

[NY]

Post by JNugent
I got my first diesel car - a new Citroen Visa 17D - in late 1986, and
kept it until 1992. That was unheard of at that time. I'd never kept a
(petrol) car that long because something always went wrong with them. But
diesels are inherently hardy, reliable and trouble-free. My current
(diesel) car, new in early 2014, shows not a single problem (touch wood)
eight-and-a-half years later.

My previous car, a Peugeot 306 2.0 HDi had done 160,000 miles when I sold it
from new after 10 years. My present car, a Peugeot 308 1.6 HDi, has done
190,000 miles (I bought it as the second owner when it had done 18,000) and
I've had it 14 years. It still goes like a bomb (apart from when a garage
failed to retighten the turbo output hose, but that was a few minutes to fix
once I diagnosed it!). The other week I did a 250 mile trip down south and
return a few days later, mostly on motorway, and got an average of 58 mpg
from driving mainly at 70 mph for those 500 miles. Not too bad ;-)

The 306 only had normal expenses. The most expensive was a "fan belt",
twice - the first garage failed to notice a warped pulley which may even
have caused the first belt to break. The 308 has had normal expenses, apart
from one biggie when it needed a new diesel particulate filter and catalytic
converter at about 140,000 miles - that's probably the only diesel-specific
cost.

What has improved no end since the early 1980s when I bought my first car,
is rust-proofing: my first car, a 1980 Renault 5, suffered bad rust and the
beginnings of structural corrosion, after about 40,000 miles. I've not seen
any rust on the last three cars I've had and corrosion has never been
mentioned at any service or MOT (the car is old enough that I ask garages to
check for it). The fact that a lot of body panels on modern cars are plastic
rather than steel probably helps ;-) Amazingly it's still on its original
clutch and shock absorbers; neither need replacing yet (again, I've got my
garage to inspect the shocks, just in case).

Both cars had their cambelt changed at the stated interval (around 100,000
miles) which is not cheap, but again is an expense that any car, petrol or
diesel, will need unless it has a chain rather than belt.