Iran war: A week’s worth of fuel stock includes dregs at bottom of tanks
Tuesday, 31 March 2026
Estimates of the country’s fuel stocks include several days’ worth of fuel that are dregs at the bottom of tanks that can’t easily be used, officials have confirmed.
It is normal practice to install fuel outlets part way up storage tanks, so that any sludge, water and other contaminants that might otherwise compromise the quality of fuel can settle undisturbed at the bottom of the tank.
The Ministry of Business, Innovation and Employment (MBIE) has confirmed that both fuel importers’ “minimum stockholding obligations” and the estimates of in-country fuel supplies that the ministry has been updating on a twice-weekly basis include this so-called “heel storage”.
A study commissioned by MBIE and published last month estimated that just over seven days’ worth of petrol and about three days’ worth of diesel and jet fuel stored in New Zealand was heel stock that could not normally be accessed.
Read more:
“Heel stock can be removed when tanks are cleaned for maintenance, but this is a slow operation with the heel fuel removed from the tank via smaller pipes such as those used for water draw-off,” the report said.
“We treat this stock as unavailable for normal disruption response, although some could be accessed in a severe emergency.”
MBIE reported on Monday that the country had almost 28 days’ worth of petrol and 22 days’ worth of diesel in storage.
But this would be reduced to about 21 days and 19 days, respectively, if heel stock was excluded, according to the estimates in the February report.
“MBIE’s published stock and storage capacity figures are reported on a gross basis consistent with the ‘minimum stockholding obligation’, meaning they include heel stock,” an MBIE spokesperson said.
On the flip-side, he noted they excluded fuel held at service stations and truck stops, saying “they are considered a reliable indicator of fuel available across the supply system”.
MBIE’s latest fuel-stock figures suggest the country’s storage tanks could come relatively close to capacity over the next few weeks.
Fuel importers had the capacity to store 420 million litres of petrol, 434 million litres of diesel and 198 million litres of jet fuel, its spokesperson said. Those figures also include heel storage.
Based on 2024 consumption figures, that would be enough for 52 days’ petrol storage, 40 days’ diesel storage and 39 days’ jet fuel storage.
As at April 17, the country should have about 36 days of petrol, 31 days of diesel and 27 days of jet fuel in store, based on MBIE’s tally of planned shipments and assuming average fuel demand.
However, the data does not preclude stocks peaking at a higher level before then.
That would appear to be a reason why the Government may be holding back on conservation measures for now.
“There is a risk that a material reduction in demand while we still have sufficient supply would mean incoming ships having to wait for stocks to reduce before discharging their cargoes,” MBIE’s spokesperson said.
Finance Minister Nicola Willis, who heads the ministerial group overseeing fuel security, said on Monday that the Government was doing “everything needed to protect fuel security for the future”.
“There’s a limit to how much storage we have now, so stopping fuel flowing wouldn’t necessarily put us in a better position.”