UPDATE: GRAIN farmers in the swing of harvest are getting smaller allocations of diesel after storms disrupted supply from refineries.

Victorian Farmers Federation grains president Andrew Weidemann said the shortage of supply was probably being noticed more at service stations but farmers weren't getting their full allocations.

He said he'd received an unconfirmed report a fuel company was moving diesel into Victoria from Sydney to deal with shortages.

"It does have an impact. Farmers can't get their full allocation. But I guess it’s about keeping the wheels rolling (at harvest)," he said.

He said harvest was moving south and depended on the weather.

He'd heard some farmers getting 1500 to 2000 litres and of a farmer receiving diesel contaminated with petrol who was hunting for more diesel.

Mr Weidemann said harvesters with 1000-litre tanks could be emptied in 16 hours.

He said farmers often used several harvesters, chaser bins and trucks, which needed diesel this time of year.

"Lucky in our own situation we filled up earlier in the week."

Mr Weidemann said he heard reports diesel supplies at service stations in Bendigo and Colac were low.

Recent storms in Melbourne caused local refineries to shut down production, and reopened facilities are still not at full capacity, Australasian Convenience and Petroleum Marketers Association chief executive Nic Moulis said today.

"My members are concerned that if this continues for too long then as we run into the Christmas holidays and peak period, we won't be able to satisfy our customers' need for fuel," Mr Moulis said.

It is believed once Shell repairs its production fault over the weekend it may take a few days for the fuel to filter through the supply chain.