Petrol is not as badly affected and it's not generally as strategically important - diesel = tractors, trains, trucks, cargo ships and generators.
The issue is about diesel refining capacity now.
Iraqi had increased production of crude to make up a lot of shortfall and are trucking it under (expensive) escort through Syria. At present this route is holding but it's very vulnerable. There's been recent riots in Syria due to fuel prices going up. Plus one of the attacks on Saudi Arabia was from dissident Iran supporting Iraqis on Iraqi soil.
The Saudis were still getting a significant amount of crude and distillates out but this has massively reduced since the attacks and they've taken to trucking under escort to Oman. Again this is a vulnerable route which hasn't yet been targeted by Iran, but this is possible. And it uses diesel. The Saudi diesel refinery capacity has been knocked out plus they are now needing more to get oil out of the country, to the point that the Saudis have been looking to buy diesel from Europe (think about this - they are exporting oil all the way to Europe using diesel only to import it back as diesel. This is something of a death spiral and you'd only be doing this in desperation).
The US largely have enough refinery capacity to cover their own needs but it's not quite this simple. They do import some from Canada for example (because it's closer and cheaper to do this than get from the Gulf of Mexico). But the refineries are running at max capacity and it's nearly maintenance season (also remember that the refineries are in hurricane areas - though this year they've been so far fortunate on that front). One of their larger refineries had an issue and has been shut down for a couple of days this week pushing up prices in the Midwest. This should be back online soon but they can't really afford for it not to be running.
The US is talking about banning diesel exports - the problem with this would be it would push up prices worldwide as a result. It would initially help the US but eventually backfire because the problem the US really has isn't a shortage of diesel but a shortage of cheap diesel. The USA imports cheap diesel and exports expensive diesel to places like the UK. Other countries would have to respond to this change in the market as the US would be no longer assumed as a reliable source and this would have an overall negative impact to what they are trying to achieve (reduce prices) and led to countries strategically changing tactics and infrastructure. It would long term be a negative for the US.
The US had also used reserves to help keep prices lower but they have a limited amount they can do this with.
Then Libya has put three refineries off line this week due to civil unrest. Italy imports 25% of its diesel so they are a fairly significant producer for the EU market.
The amount of oil getting out via Oman and Hormuz has been increasing but this hasn't been enough to make up for what the Saudis were putting through the red sea. It's also in crude form not refined as diesel.
Given the situation has been going on for some months of disruption, there's been a slow grind on reserves around the world.
Note: due to gas shortages from Qatar due to Iranian strikes on Pakistan and Bangladesh have been using generators to help with power outages there. So consumption of diesel has also gone up there.
Diesel is the real issue because it takes refining and it powers the key trades. The margins are tighter on amounts than crude itself.
Macron has asked to convene at emergency G7 about the crisis and is looking to release some of Europe's strategic reserves (held in diesel and petrol rather than crude) but this will only ease the situation temporarily.
Longer term there will potentially be a point where there are shortages and these slowly spread. There are already shortages in a couple of countries (the Philippines has had issues already and I believe there's rationing already).
A US export ban would cripple Australia. I believe Australia is one of the most exposed countries at this point.
The UK has four refineries which account for 50% of our consumption with the majority of the rest coming from the Netherlands. The rest comes from the US and the middle east. But apparently we are less exposed than other parts of Europe, at least currently.
And yes I now can bore the tits off everyone on something else inane.