"A couple of young blokes, a WRX, a P-plate, not having money between the both of the them. I thought: 'Crikey', you know,'' he said.

Two teenagers led police on a two-hour, 200-kilometre car chase, driving around road spikes and escaping down a dirt road.

Lithgow Police today arrested two teenagers about 5.10am after a Lithgow service station worker became suspicious.

The service station worker, Tony Inzitari, told smh.com.au the two young men dropped into the Shell service station on the Great Western Highway at 5am claiming they had no money and needed $20 worth of petrol.

One of them told him his mate had lost his wallet in Mudgee and could leave his own wallet at the service station until they returned to pay the $20 back.

"If they're stuck on the road I try to get them on their way,'' he said.

But a few peculiar details pricked Mr Inzitari's suspicions and he decided to call up the police while one of the men filled the white Subaru RS with petrol.

"A couple of young blokes, a WRX, a P-plate, not having money between the both of the them. I thought: 'Crikey', you know,'' he said.

He phoned the police and gave the details of the car.

"If it was stolen at least you've got a chance to get your 20 bucks back,'' he said.

"By the time I got off the phone the police had already arrived here and arrested them.''

Police called off the initial pursuit for safety reasons, after two patrol cars pulled out with faults - one with a broken radiator, the other with a faulty siren.

The chase began when police tried to stop a Subaru RS at St Marys about 8.30pm yesterday and raced after it to the Bells Line of Road. The car allegedly had no registration plates.

But the Subaru drove around the road spikes put down at the weighbridge at Bell in the Blue Mountains.

Lithgow Police then took over the pursuit, through Lithgow to Mudgee, and down the Castlereagh Highway.

It was there police called it off for safety reasons after the Subaru turned onto a dirt track.

Explaining the faults in the two police cars, Chifley Local Area Command Superintendent Martin Wookey said: "We [NSW Police] have a fleet of I think 14,000 and the cars are new and well maintained but sometimes there are faults."

The Polair police helicopter tracking the alleged offenders also had to pull out of the chase because of the terrain and rising fog, he said.

The crew did not have maps of the area.

"It [Polair] took off from its base on another job then they were advised about the pursuit," Superintendent Wookey said.

"They can't carry every map because the helicopter wouldn't be able to take off so they only take the ones they need.

"In this instance they were coming from another job and didn't have the right maps with them."

Superintendent Wookey said: "With a pursuit over two hours over 200 kilometres and no injuries or damage to property, I am very proud of them [the officers]," he said.