An Alice Springs social worker says a new petrol variant that will not make sniffers high will be useless if they can get regular unleaded at a nearby roadhouse.

Blair McFarland from the Central Australian Youth Link Up Service is calling on the federal Health Minister to expand his promised subsidy for the new Opal Unleaded.

He says it should apply to all roadhouses within 30 kilometres of Indigenous communities affected by sniffing, as owners will not make the switch without government help.

"They're obviously not going to want to be involved now, if the retail price of the petrol is 40 cents a litre more than standard unleaded," he said.

"But those roadhouses are probably going to be receptive if it's not going to have to be a cost to them and certainly roadhouses like the one at Mt Ebenezer that's owned by an Aboriginal community organisation and the same at Hermannsburg."

He says a subsidised bowser is also needed in Alice Springs for people travelling to the communities.

"That'd cut down on their car being a target for young people who keep an eye on cars coming into the community and go and bleed them for petrol, if they're in an Avgas community," he said.

"So that would give some protection for people going out to those communities.

"If there was a sticker on their car saying, 'this car's been filled up with Opal', then those young people would leave it alone."