Over the ensuing years both of these small companies prospered, distributing heating oil throughout suburban Melbourne with a small core of company drivers and subcontractors who supplemented their income over the summer months delivering for the breweries.

However, increases in the price of oil and the introduction of natural gas in Melbourne in 1969 precipitated a slow but steady decline in the heating oil market and as a result, Metro Vac and East Oil began to diversify into industrial fields. Developing their own depot networks, both companies began distributing a range of Mobil petroleum products that included gasoline, distillate, kerosene and lubricants, as well as heating oil. Designated geographical areas stretched from Euroa, in northern Victoria, to the Mornington Peninsula in the south.

By the early 1980s it became apparent that combining the businesses would provide a more cost effective and formidable force in the market place. In September 1985, Metro Vac Pty. Ltd., (including its acquisition of LPG cartage contractor, Lloyd Reynoldson a few months prior), merged with East Oil Pty. Ltd. to form Petrogas Pty. Ltd.

During the following two years the new company underwent a period of rapid expansion. This included the acquisition of service stations and another heating oil distribution company, Coulson Oil, in December 1986. The LPG operation at Somerton was also expanded. Staff were located in Head Office at Dandenong and in depots at Mornington, Mt. Evelyn, Wollert, Dandenong, Nunawading, Seymour and Richmond.

In July 1988 the Directors of Petrogas decided to enter into a 50% equity agreement with Mobil Oil Australia for the wholesale business of Petrogas. This move also encompassed the purchase of Mobil's largest distributor in Australia at the time, Campbells Metro Oil. The equity company, Petrocam Pty. Ltd. (trading as Petrogas), was established.

Since the late 1980s Petrogas has continued to streamline its logistical operations. Restructure had been facilitated by the relocation of the Petrogas Head Office in 1996 from Woolert to Mobil’s Spotswood Terminal with direct access to both of Mobil’s Melbourne fuel terminals. It also included the closure of depots, territory expansion and staff rationalisation. Product was distributed predominantly from the Mobil Spotswood Terminal with a satellite depot located at Mt. Evelyn.

On 31 December 1996 the Group sold its various divisions to separate entities and the wholesale division became Petrogas Pty. Ltd.

On 1 August 2001, former shareholder MDSS Nominees sold the remaining 50% equity to Vacuum Oil Company, a Mobil subsidiary so that Petrogas Pty Ltd became a 100% owned ExxonMobil subsidiary. During the following 5 years Petrogas operated under ExxonMobil management until a change in national policy saw ExxonMobil divest all of its shareholdings in distributorships in Australia.

On the 31st of May 2006 Petrogas once again became 100% owned by independent operators. Since then Petrogas has been striving to again be the best independent supplier of petroleum products in the Melbourne market.