Costco gas bars set the floor of the Toronto fuel market. On a typical day Costco regular runs 5–15 cents per litre under the surrounding majors, and its premium (91 octane) is usually the cheapest premium fuel in the GTA by an even bigger margin. The trade-offs are the ones every member knows: you need an active Costco membership to pump, the queues peak on weekends and weekday evenings, and payment at the pump is Mastercard or debit only.
The City of Toronto has three Costco gas bars — Scarborough at 1411 Warden Avenue (near Warden & Eglinton), Downsview at 100 Billy Bishop Way (off Wilson Avenue by the 401/Allen interchange), and Etobicoke at 50 Queen Elizabeth Boulevard off The Queensway. Ring the city and there are more: two in Mississauga (Heartland on Rodeo Drive and Dundas Street East near Dixie) and two in Vaughan (Colossus Drive by Vaughan Mills and New Huntington Road in the west end). Each location section below shows the live price where we track it.
Costco fuel is standard-spec gasoline with deposit-control additives (it meets Top Tier standards), so the discount is a business-model choice, not a quality difference — the gas bar exists to drive memberships and warehouse trips. On a 60-litre fill, a 10¢/L gap saves $6; a couple of fills a month covers a Gold Star membership over the year on fuel alone.