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Supermarket shoppers are "packing their own", switching to budget brands and buying smaller quantities as food prices continue to soar.
Motorists are bulk-buying fuel and increasingly driving off without paying for petrol.
These are the latest signs of the growing grip the economic downturn is having on our
shopping habits.
Figures released this week showed grocery prices had risen 11.8 per cent in the past year, triggering a 3.6 per cent, $43 million drop in supermarket and grocery sales in April.
Grocery giant Foodstuffs, owner of New World, Pak 'n Save and Four Square, said sales data from the past three months provided mounting evidence of changing habits.
Retail general manager Mark Baker refused to provide figures, citing commercial sensitivity.
But he said more people were shopping at Pak 'n Save, where they could pack their own groceries in exchange for a cheaper bill.
Sales of goods in the Pams and Budget ranges had risen "significantly" as consumers coped with big increases in the price of staples, such as cheese, butter, flour and bread.
Shoppers were choosing 500g blocks of cheese when previously they might have bought 750g or 1kg.
While fresh produce sales hadn't dropped, Baker said people were buying more frozen vegetables.
"This is possibly due to being able to store these and not have to make as many top-up trips to the local veggie store, keeping fuel costs down."
Health and beauty sales were strong, suggesting people were ditching department store brands in favour of cheaper options on supermarket shelves.
Similar trends were being observed at Progressive Enterprise's Foodtown, Countdown Woolworths and Fresh Choice supermarkets.
General manager of supermarket operations Dave Chambers said sales of the company's cheapest private label, Homebrand, had rocketed.
Staff had seen people spending more time in the aisles, studying store mailers as they shopped - and even carrying calculators.
"People are being forced to make value-based decisions."
One fuel company said petrol thefts had risen by about 10 per cent in the past four months.
Gull retail business manager Graham Stirk said he had seen people stockpiling petrol before one of the recent price hikes.
"Every man and his dog was out there and had all sorts of interesting containers - hopefully they have read their home insurance policies."
Stirk said Friday was previously the biggest day of the week for sales but customer counts had become price-dependent.
"People are paying more attention. Everyone knows the price of petrol now," he said.
In an internet message posted this week, one woman said her husband had caught someone trying to steal petrol from their car one night. Another said her husband's tractor tank was repeatedly drained by thieves.
More dangerously, thieves siphoned 100 litres of aviation fuel from a small plane parked at Paraparaumu Airport. The pilot became aware of the theft just before takeoff.
Caltex spokeswoman Sharon Buckland said the company had noticed a steady decline in shop sales.
"If they had come into the shop to buy bread, they'll still buy bread. But they are not treating themselves as much - they are less likely to buy the choccies at the counter."