We found the cheapest Costco gas stations in 7 Ontario cities and you can save up to 15 c/L

Hamilton

• Citywide median price: 128.9 c/L
• Costco Ancaster median price: 122.9 c/L
• Costco Stoney Creek median price: 118.9 c/L 🏆
• Costco Brantford median price: 125.9 c/L

Drivers in the Hamilton area have three Costco gas stations to choose from — and while they're all cheaper than the city average, some offered a much sweeter deal than others.

The Stoney Creek location just east of the city had the lowest median price over the month at just 118.9 cents per litre. That's a full 10 cents lower than Hamilton's citywide average of 128.9 during the same period, making it one of the best Costco gas deals in Ontario.

Ancaster was a bit pricier at 122.9, while Brantford — which isn't in Hamilton proper but is close enough we decided to count it — averaged 125.9.

Still, every location here beats the city average by a few cents any day, especially when gas is higher than usual in the rest of the city. Across the entire month, prices never went above 129.9 at any of the three locations, even though the city average hit 135.1 at one point.

But if you're looking for the cheapest gas in the Hamilton area — especially if you're on the east side of town — the Costco in Stoney Creek is hard to beat.

London

• Citywide median price: 128.1 c/L
• Costco N London median price: 121.9 c/L
• Costco S London median price: 119.9 c/L 🏆

London drivers have two Costco options, and both are solid choices compared to other gas station brands.

The South London location won the area by a hair with a median of 119.9, versus North London's 121.9. That might not seem like a huge difference, but it can add up over time if you're filling up regularly.

What's more impressive is that both locations were consistently 6 to 8 cents cheaper than the citywide average of 128.1. And while the rest of the city never had an average price lower than 126.6, both Costco stations dipped down as low as 117.9 on multiple occasions.

So no matter which part of the Forest City you're in, filling up at Costco can definitely save you some cash — and you can rest easy knowing it doesn't really matter whether you head north or south.

Ottawa

• Citywide median price: 128.9 c/L
• Costco Gloucester median price: 123.9 c/L 🏆
• Costco Nepean median price: 123.9 c/L 🏆
• Costco Barrhaven median price: 123.9 c/L 🏆

Over in Ottawa, the city's three Costco gas stations — in Gloucester, Nepean and Barrhaven — are basically interchangeable, price-wise. Over the month we tracked, all three hovered around 123.9 cents per litre on average. In fact, most days, all three stations had the exact same price.

Of all the major cities we looked at, Ottawa had the smallest gap between Costco prices and the city average, making it the least impressive deal overall. Compared to Ottawa's citywide median of 128.9, every location was about 5 cents cheaper — not nothing, but probably not worth making a big detour if there isn't already a Costco along your commute.

That said, there were a few days when Costco was an even better deal. While the average citywide price never dipped below 127.3 during the 31-day period, Costco's prices went as low as 119.9 a few times — savings of 7.4 cents on a good day.

Toronto

• Citywide median price: 130.6 c/L
• Costco Etobicoke median price: 124.9 c/L
• Costco NW Toronto median price: 122.9 c/L 🏆
• Costco Scarborough median price: 124.9 c/L

Gas in Toronto is usually more expensive than other parts of Southern Ontario, and the citywide median during our study was a hefty 130.6 cents per litre. But Costco gas stations in the city (and across the GTA) offered a pretty wide range of prices.

The cheapest was at Northwest Toronto, with a median of 122.9 — nearly 8 cents lower than the city average. Scarborough and Etobicoke both had medians of 124.9, which still beat the city average by a decent margin. (The Thorncliffe Park and Downsview warehouses don't have gas stations.)

While Northwest Toronto reigned supreme overall, when it came to the lowest single-day price, Scarborough was unbeatable. The cheapest price we saw at this station was 116.9 — on a day when the Toronto city average was 130.8, no less. In fact, Scarbrough's prices were the most volatile in the province, with a 16.4-cent difference between the highest and lowest prices recorded throughout the month.

So if you're in Toronto and want the best deal, Northwest is your best bet on average — but you never know when you might snag an even better deal in Scarborough. Either way, any of the three locations will save you money compared to your typical gas station in the city.

GTA west (Mississauga)

• Costco N Mississauga median price: 118.9 c/L 🏆
• Costco C Mississauga median price: 119.9 c/L

Mississauga has two Costco gas stations, and both clocked in as the cheapest in the whole GTA. North Mississauga's median price across the month came in at just 118.9 cents per litre, while Central Mississauga was only slightly higher at 119.9 (and South Mississauga doesn't have a gas bar).

Compare that to the Toronto median of 130.6, and you're looking at savings of more than 10 cents per litre on every fill-up.

But while North Mississauga had the better deal on average, Central Mississauga recorded some of the cheapest single-day prices in the country. On one day, the price there dipped as low as 113.9 — nearly 15 cents cheaper than the Toronto average of 128.6 on the same day.

Either way, when compared to the Etobicoke Costco (the next-closest one on the Toronto side), both Mississauga locations were noticeably cheaper. If you live in the west end of Toronto or the GTA, filling up at a Costco in Mississauga is a no-brainer.

GTA east (Ajax & Oshawa)

• Costco Ajax median price: 124.9 c/L
• Costco Oshawa median price: 122.9 c/L 🏆
• Costco N Oshawa median price: 122.9 c/L 🏆

On the eastern side of the GTA, Costco gas prices were solid, albeit closer to Toronto's Costco prices than Mississauga's.

Oshawa's two locations tied for the cheapest price in the area, each with a median of 122.9. Meanwhile, Ajax came in just slightly higher at 124.9.

When you compare that to the Scarborough location — which is geographically the closest Toronto Costco to this area — Oshawa is a better deal, and Ajax is comparable. They're also all around 6 to 8 cents lower than regular gas stations in Toronto.

Our data also showed that Oshawa occasionally has some especially good days. The lowest recorded price at both Oshawa stations was 117.9 — more than 10 cents cheaper than the lowest reported Toronto average, which never dropped below 128.3. So while the median difference is already decent, there are days when the savings get even better.

If you're east of the city, Oshawa is your best bet for a good deal — especially if you time it right.

GTA north (Vaughan & Newmarket)

• Costco East Gwillimbury median price: 124.9 c/L
• Costco Vaughan median price: 123.9 c/L
• Costco NW Vaughan median price: 122.9 c/L 🏆

Costco stations in the northern GTA were surprisingly consistent. Medians hovered around the same range: East Gwillimbury came in at 124.9, while Vaughan and Northwest Vaughan averaged 123.9 and 122.9, respectively. (Richmond Hill and the two Costco locations in Markham aren't included because they don't have gas stations.)

The East Gwillimbury station was still open during the month of our study, but has since temporarily closed for its conversion into a Costco Business Centre. Meanwhile, the brand-new Newmarket location hadn't opened yet — but since it's just minutes away from East Gwillimbury, we've included that station here to give a rough idea of what Newmarket prices might look like now that it's up and running.

Price-wise, this area is in line with what we saw in Toronto and the eastern GTA, but with less volatility. The lowest price recorded in the northern GTA was 119.9 — not quite as low as Scarborough's 116.9 or Oshawa's 117.9.

But what it lacked in extreme deals, it made up for in predictability. Price swings were small here, with only an 8-to-10-cent range over the month — compared to Scarborough, which swung by a whopping 16.4 cents.

Everywhere else

• Costco Barrie median price: 123.9 c/L
• Costco Guelph median price: 123.9 c/L
• Costco Niagara Falls median price: 119.9 c/L
• Costco Orillia median price: 119.9 c/L
• Costco Peterborough median price: 118.9 c/L 🏆
• Costco Sudbury median price: 126.9 c/L
• Costco Waterloo median price: 122.9 c/L
• Costco Windsor median price: 122.9 c/L

Outside the biggest metro areas, some of the cheapest Costco gas in Ontario could be found in places like Peterborough, which came in at just 118.9 — tied with North Mississauga and Stoney Creek for the lowest median in the entire province.

Niagara Falls and Orillia also posted strong numbers, each averaging 119.9 cents a litre.

Meanwhile, unsurprisingly, Sudbury was the most expensive location in Ontario, with a median of 126.9 — still cheaper than Toronto's citywide median, but higher than other Costcos in the province.

Windsor, Guelph and Waterloo stood out for having the most stable prices in the province over the month, with only a 7- or 8-cent difference between their highest and lowest recorded prices. By contrast, Niagara Falls — while cheaper overall — saw a lot more fluctuation, with a 12-cent swing from its cheapest day to its most expensive.

So while Ontario's smaller cities might not get as much attention, they're often where you'll find some of the best prices — and the most consistent ones too.