More people have been filling up at petrol stations as prices climb.  

The Waitomo Group says there's been a 15-20% increase in demand in the past week. 

Chief Executive Simon Parham says pump prices have gone up from about 10 to 20 cents a litre.  

He told Mike Hosking it's because they buy their product on a weekly basis.  

Parham says with short sharp shocks it's very hard to avoid price increases. 

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