The service station chain's inventories were $294.2 million at the end of the 2014 calendar year, down form $509 million in 2013.
The industry is currently undergoing rationalisation, with NZX-listed Z Energy seeking competition regulator approval to buy the rival Caltex and Challenge! brands from Chevron New Zealand for $785 million, adding 147 service station and truck refuelling depots to its existing 200 outlets.
The merged entity leapfrog BP as the biggest transport fuel retailer in the country, with about 49 per cent of the market and annual sales of more than $5.8 billion.
There are about 236 BP-branded petrol stations across New Zealand, of which 80 are owned and operated by the arm of the global company, with the remainder dealer-owned.
In its submission to the Commerce Commission, Z argues both BP and Mobil will be competitive constraints on its behaviour as their global parents provide ample resources to prevent New Zealand-owned Z from exercising market dominance if the acquisition goes ahead.
BP New Zealand completed its acquisition of Rural Fuel in the 2014 financial year, acquiring goodwill value of $53.2 million from the purchase.
Palmerston North-based Rural Fuel delivers petrol to farmers, contractors and transport operators across the lower and central North Island.
BP valued the investment at $57 million at the December 31 balance date, having raised its investment to 100 per cent from the 40 per cent share it had held since 2007.
The service station chain said it faces backdated excise duty claims from New Zealand Customs Service in relation to Wiri Oil Services, a joint venture between the four major fuel companies, and BP's terminals that aren't operated by Wiri.
The assessments relate to "prior years up to and including 2014" and are being disputed, BP said.