Does Costco Sell Diesel? Which Locations Have It (and DEF)

If you drive a diesel pickup, SUV or motorhome, the first question about Costco gas is simple: does Costco have diesel at all? This post answers that, lists every Costco station in our data that sells diesel in the US and Canada, and covers how to check a station yourself, what is in Kirkland Signature Diesel, whether it is cheaper, and where Costco sells diesel exhaust fluid (DEF).

Short answer: Yes, Costco sells diesel, but only at a minority of its gas stations. As of our September 29, 2026 reading, 67 of 593 US Costco stations we track (about 1 in 9) and 6 of 78 Canadian gas bars posted a diesel price, mostly in the West. Costco does not sell DEF at the pump, but many warehouses stock 2.5-gallon (9.46 L) boxes of it.

Does Costco sell diesel fuel at every gas station?

No. Most Costco stations sell only two gasoline grades, regular and premium. Costco's own diesel page describes Kirkland Signature Diesel as "available at select Costco locations", and our data shows how select that is.

Diesel is concentrated in the West. California has 18 diesel stations, Washington 12, Texas 7, Utah 6 and Oregon 3. East of Ohio and Kentucky, we found none: no Costco in Florida, New York, Georgia, Virginia or the Northeast posts a diesel price in our data. Minnesota, which has a large Costco footprint, also has no diesel station in our data.

Costco's diesel page on costco.com had 63 US warehouses listed when we checked on September 29, 2026. Our data shows four more, all opened in 2025 or 2026: Richland, WA, Syracuse, UT, South St. George, UT and New Braunfels, TX. The page likely lags new openings, so treat either list as a guide and confirm with the warehouse.

Why do only some Costco stations have diesel?

Costco has not said publicly why it sells diesel at some stations and not others. A September 2025 SlashGear piece noted the company "has not disclosed the reason" and that explanations online are guesses. So what follows is what the data shows, not Costco policy.

• Location type. Many diesel stations serve regional hubs with lots of pickups, farm vehicles and RVs: Bismarck ND, Billings and Kalispell MT, Gypsum CO, Traverse City MI, Midland and Lubbock TX, Idaho Falls ID, Redding and Visalia CA.
• Newer builds. About 43% of diesel stations in our data opened in 2014 or later, compared with 29% of all US Costco stations.
• Not Business Centers. It is tempting to assume Costco Business Centers carry diesel for commercial customers. In our data only 2 of the 13 Business Centers with gas stations sell diesel: Commerce and Hawthorne in Southern California. The Lynnwood, WA Business Center does not, while the regular Lynnwood warehouse does.

Diesel also needs its own underground tank, pump hardware and supply contract, so adding it is a site-by-site decision. Stations can also stop selling it, which is another reason to check before a long detour.

How to check if your Costco has diesel

There are three quick ways, from most to least official.

1. Costco's warehouse locator. Open your warehouse on costco.com or costco.ca (or in the Costco app) and look at the gas section. Stations that sell diesel show a diesel price next to regular and premium. No diesel line means no diesel.
2. Costco's diesel page. The Kirkland Signature Diesel page lists US diesel locations by state. Costco also takes diesel questions by email at KirklandSignatureFuel@Costco.com.
3. Our station pages. Every station page on this site shows today's price by grade and 30 days of history. If a station sells diesel, you will see a Diesel row. Start from the station finder or the US and Canada hubs.

Diesel pumps keep the same hours as the rest of the station. See Costco gas hours for opening times, and note that you need a membership card to pump, covered in our membership post.

Which Costco locations sell diesel in the US?

These are all 67 US stations posting a diesel price in our data, with each station's diesel price as of September 29, 2026. Each link opens that station's page with today's price and 30-day history.

Prices are rounded to the cent and change daily. The cheapest Costco diesel in our data was New Braunfels, TX at $5.55; the most expensive was $8.00, posted at 12 California stations. State pages for the biggest diesel markets: California, Washington, Texas, Utah and Oregon.

Does Costco sell diesel in Canada?

Yes, at a handful of gas bars. Six Canadian Costco locations in our data post a diesel price, spread across five provinces. Costco.ca's gas station listings include diesel as a fuel type where it is sold.

Prices as of our September 29, 2026 reading. The Canadian average of 247.1¢/L compares with roughly 264¢/L nationally, per Natural Resources Canada figures reported by BNN Bloomberg the same day. Those six gas bars are mostly in lower-priced Prairie markets, so the gap flatters Costco somewhat. Province pages: Alberta, British Columbia, Ontario.

Is Costco diesel cheaper than other stations?

Usually, yes, by roughly 20 to 45 cents a gallon in the states where it sells the most diesel. We compared each state's Costco diesel average from our data with AAA's statewide diesel average for the same day.

Costco figures are from our September 29, 2026 reading; AAA figures are AAA's "current average" viewed the same day.

Two cautions. First, the national numbers are misleading on their own: Costco's average of $6.85 is above AAA's national diesel average of $6.44 and EIA's weekly average of $6.38 (week of September 28, 2026) because most Costco diesel is sold in California and the Pacific Northwest, where diesel costs more everywhere. Compare state to state, or station to station. Second, diesel costs a lot more than gasoline right now. At the same Costco, diesel ran a median $1.92/gal above regular, and the average Costco diesel price rose about $1.00 over the 30 days to September 29. AAA lists its all-time high national diesel average as $6.53 on September 22, 2026. For how Costco keeps pump prices low in general, see why Costco gas is so cheap.

Is Costco diesel Top Tier?

Yes. Top Tier has a separate diesel standard, created in 2017 and backed by automakers and engine makers including GM, Ford and Daimler Truck. Costco / Kirkland Signature is on Top Tier's list of approved diesel brands for the USA, Canada, Mexico, Puerto Rico and Japan, and Costco's diesel page carries the Top Tier Diesel logo.

The diesel standard goes beyond detergents. It requires additives for injector deposits and lubricity, higher oxidation stability, a water detection process at the station, and dispenser filters (10 micron on low-flow pumps, 30 micron or finer on high-flow). Top Tier notes that approval can be site-specific, so not every station of a brand is automatically covered. Costco says it adds deposit control additives to its diesel even though "deposit control additives in diesel fuel have not been mandated by the EPA". Like all US on-road diesel, it is ultra-low sulfur diesel (15 ppm sulfur). For Costco gasoline's Top Tier status, see is Costco gas Top Tier.

Does Costco diesel contain biodiesel?

Only as much as state law requires, according to Costco. A Costco diesel FAQ answer, quoted by customers on the TractorByNet forum, says Kirkland Signature Diesel "only contains biodiesel where required by law". We could not load that FAQ page on costco.com on September 29, 2026, so treat this as Costco's past wording.

What that means in practice:

• Anywhere in the US: diesel can contain up to 5% biodiesel (B5) without a special pump label. Blends above 5% must be labeled with a "B" number.
• Oregon: state law requires at least B5 in all diesel, and renewable diesel can count toward it. That affects the three Oregon Costco diesel stations.
• Washington: at least 2% of diesel sold must be biodiesel or renewable diesel.
• Minnesota: requires B20 from April to September, but no Minnesota Costco sells diesel in our data.

If your engine maker limits biodiesel content, read the label on the pump. A blend above B5 has to say so.

Can trucks, trailers and RVs fit at Costco diesel pumps?

Pickups and vans generally can. Costco diesel pumps are ordinary passenger-vehicle dispensers, and under the SAE J285 practice, diesel nozzles have a larger spout (about 15/16 inch) than unleaded ones (13/16 inch). Light-duty diesel trucks and cars are built for that nozzle. Costco does not run separate high-flow truck lanes like a truck stop.

Large motorhomes and trailers are a judgment call. Costco does not publish canopy heights, and its fuel lanes can be tight and busy. One RVer on RV LIFE reported a nominal 13 foot 6 inch clearance at one Costco, and another described needing a sharp turn to exit the Bakersfield station. If your rig is close to 13 feet tall or you are towing, scout the station on a map first, go early in the morning, or use a truck stop. Semi-trucks are not practical at Costco.

Does Costco sell DEF (diesel exhaust fluid)?

Yes, in jugs, not at the pump. We found no Costco station listing DEF at a dispenser, and Costco's diesel page does not mention it. What Costco does sell:

Prices vary by warehouse and promotion, and online listings sometimes show as unavailable, so check the Costco app for your warehouse. At those prices a 2.5-gallon box works out to roughly $4.40 to $6.80 a gallon.

Frequently asked questions

Does Costco have diesel gas at every warehouse?

No. As of September 29, 2026, only 67 of 593 US Costco stations and 6 of 78 Canadian gas bars in our data sold diesel. Check the gas section of your warehouse on costco.com, costco.ca or the Costco app: stations with diesel show a diesel price.

How many Costco locations have diesel?

Our data shows 67 US stations in 21 states and 6 Canadian gas bars in 5 provinces as of September 29, 2026. Costco's own US diesel page listed 63 warehouses the same day, missing four locations that opened in 2025 and 2026.

Which state has the most Costco diesel stations?

California, with 18 stations posting a diesel price in our data, followed by Washington with 12, Texas with 7 and Utah with 6. Most other states that have any Costco diesel have only one or two stations.

Do I need a Costco membership to buy diesel?

Yes. Costco diesel pumps work the same as its gasoline pumps and require a valid membership card at the pump. The same payment rules apply as for gas.

Is Kirkland Signature diesel good for my engine?

Kirkland Signature Diesel is on Top Tier's list of approved diesel brands in the US and Canada, which requires detergent and lubricity additives beyond the basic fuel specification. It is ordinary ultra-low sulfur diesel that meets the same fuel standards as other on-road diesel.

Can I put DEF in at a Costco gas station?

Not from a pump. Costco stations do not have DEF dispensers, but many Costco warehouses sell 2.5-gallon (9.46 L) boxes of DEF, such as PEAK BlueDEF, which you can pour in yourself using the included spout.

Is Costco diesel more expensive than regular gas?

Yes, by a lot in 2026. At the same Costco station, diesel cost a median $1.92 per gallon more than regular in the US and about 73¢/L more in Canada as of September 29, 2026.

Sources

• Kirkland Signature Diesel, Costco — "available at select Costco locations", the US diesel location list by state, Top Tier Diesel logo, additive claims, KirklandSignatureFuel@Costco.com contact.
• Costco Gasoline and fuel promise, Costco — Costco's statement that deposit control additives in diesel are not EPA-mandated but included.
• TOP TIER Approved Diesel Brands, Top Tier — Costco / Kirkland Signature listed for the USA, Canada, Mexico, Puerto Rico and Japan; diesel standard requirements and sponsors.
• Gasoline and Diesel Fuel Update, U.S. Energy Information Administration — US on-highway diesel average of $6.382 for the week of September 28, 2026, and regional averages.
• AAA Gas Prices, AAA — national diesel average of $6.44 and the record of $6.53 on September 22, 2026; state diesel averages for California, Washington, Texas and Utah.
• Now at historic highs, diesel prices poised to hit consumers even harder, BNN Bloomberg — Natural Resources Canada retail diesel average above $2.64/L on September 29, 2026.
• Does Costco Sell Diesel Fuel?, SlashGear — Costco has not disclosed why only some stations sell diesel.
• Diesel Fuel Standards and Rulemakings, US EPA — all US highway diesel is 15 ppm ultra-low sulfur diesel.
• Biodiesel Laws and Incentives in Oregon, Washington and Minnesota, Alternative Fuels Data Center (US DOE) — state biodiesel blend requirements and B5 labeling rules.
• Anyone using Costco diesel fuel?, TractorByNet forum — customer-quoted Costco FAQ wording on biodiesel (forum report).
• SAE J285 Gasoline Dispenser Nozzle Spouts, SAE International — nozzle spout diameters for unleaded versus other fuels.
• Plan and Practice Accessing Fuel Stations with Your RV, RV LIFE — reader reports of Costco canopy clearance and the Bakersfield diesel station (forum-style comments).
• PEAK Blue DEF Diesel Exhaust Fluid, 2.5 Gallon, Costco Business Delivery and HD Expert DEF 9.46 L, Costco.ca — Costco DEF products, item numbers and specs.
• PEAK BlueDEF 2.5 Gallon (#1111266), Warehouse Runner and Costco East Fan Blog — third-party in-warehouse DEF price reports for the US and Canada.