Why is diesel becoming more expensive then petrol

Timing apparently, petrol will pass out diesel again soon

That's why.

Finally refining margins have fallen. They are now just under $25. Still way above the normal $6-$12 range they have traded for years. Petrol is circa $16 (historically $9-$14)

Finally found a site that can show the two products and doesn't require registration https://www.neste.com/investors/market-data/oil-product-margins#21b4d81e

$25 still is about 16c+vat a litre, but down from the crazy 29c + vat from 10-12 days ago and down from the mid 30's from the last few days. So diesel should fall a further 12-15c in the next week. Same for kerosene. I expect up here in NI it will fall to about £800 for a fill and in the south the extra vat and carbon tax means circa €1150 for 1,000 litre

Diesel refining margins now down to $19. Combined with oil price drop, some real decent drops coming. At least 15/16p up here or about 20c in euro down south in the next week or so

The cynic in me says - more diesel cars more expensive diesel= more money for our friend the revenue commissioner.