Euro Garages has picked up 48 company-owned service stations in the Midlands and eastern England, and 36 company-owned service stations in south-west England and south Wales will be sold to Rontec Investments LLP.
In a statement the oil company said it expected both sale and transfer agreements to be completed in the second quarter of this year.
On-site staff and a small number of above-site retail operating company personnel will transfer to Rontec and Euro Garages.
The sale is part of Esso's move to a branded wholesale business model in the UK retail market and follows sell-offs of packages of other forecourts last year. Further sales are expected but Esso was remaining tight-lipped about details.
The company said ExxonMobil will continue to serve the retail market in these regions, with Rontec and Euro Garages supplying Esso-branded fuels to their respective sites.
The deal means Euro Garages has more than doubled the size of its estate in the space of a year to almost 180 sites. It follows the purchase of 45 Esso sites in the north of England and North Wales, completed last January, and the company said it was on target to exceed 200 during 2014.
Euro Garages chief executive Zuber Issa added: "We will be looking at further acquisitions and establishing strategic alliances to grow our UK presence and continue to change the market perception of forecourt retailing."