Yes, Kirkland full synthetic is a good oil for most gasoline cars. The 0W-20 and 5W-30 carry the same API SP, ILSAC GF-6A and GM dexos1 Gen 3 approvals as name-brand synthetics, and they cost about half as much per quart.
The catch is narrow. If your owner's manual names a specific carmaker approval that isn't printed on the jug, buy an oil that has it.
Who makes Kirkland oil
Costco doesn't make it. Jalopnik reports that Highline Warren, formerly Warren Distribution, is the official supplier of Kirkland Signature motor oil. Highline Warren was founded in 1922, owns brands like Mag 1, Prime Guard and Rain-X, and distributes Mobil 1 filters and lubricants.
You'll also see "Warren Oil" named on SlashGear and Rick's Free Auto Repair Advice. That's a different company. On Bob Is The Oil Guy, a 2023 thread on this exact question ended with members pointing out that Highline Warren and Warren Oil are separate firms and the two names get mixed up constantly.
For the buyer, the brand behind the blend matters less than the licenses on the label. API and GM don't care who blended it. They care whether it passed their tests.
Is Kirkland synthetic oil good
Yes, for what most people drive. The approvals and the lab numbers both back it up.
What the jug is licensed for
Costco's own product page for the 0W-20 and 5W-30 full synthetic lists these:
Approval | What it means | Kirkland 0W-20 and 5W-30 |
|---|---|---|
API SP | Current API gasoline category | Yes |
API SN PLUS, SN, SL | Older API categories, backward compatible | Yes |
ILSAC GF-6A | Current ILSAC fuel-economy standard | Yes |
GM dexos1 Gen 3 | GM's own spec, required for GM gas engines | Yes |
API CK-4 | Heavy-duty diesel category | Not listed |
European OEM specs (BMW Longlife, VW 50x, MB 229.x) | Carmaker approvals for European engines | Not listed |
Costco also says the oil helps prevent low-speed pre-ignition (LSPI) in turbocharged direct-injection engines, and controls wear better than the API SP minimum during cold starts.
Older reviews undersell this. SlashGear's write-up lists API SN Plus and ILSAC GF-5, which were the previous standards. The current jugs carry SP and GF-6A, so check the label on the jug you actually buy.
How it tests against Mobil 1
The Petroleum Quality Institute of America (PQIA) buys oils off the shelf and tests them. Jalopnik pulled two of PQIA's figures for the 5W-30 full synthetics:
Test (PQIA, 5W-30 full synthetic) | Kirkland | Mobil 1 |
|---|---|---|
Viscosity at 212°F | 11.6 cSt | 11.2 cSt |
Zinc (anti-wear additive) | 870 ppm | 868 ppm |
Both are inside the 5W-30 window and the zinc is effectively identical. Jalopnik's author calls the differences minor and admits the comparison is cherry-picked. That's the honest read. These are two oils built to the same standard, landing in the same place.
PQIA also found the Kirkland 5W-30 conformed to its stated API service ratings, per Jalopnik. The YouTube channel Project Farm ran Kirkland against Walmart's Super Tech on evaporation, cold flow and film strength, and SlashGear reports they finished very close in every category.
What nobody has published is a long-term engine teardown. That's true of almost every oil, Mobil 1 included.
What owners argue about
The fights on forums aren't about whether it meets spec. They're about whether "meets spec" is enough.
On a 2025 Bob Is The Oil Guy thread about a turbo Subaru Outback, one staff member said he wouldn't use Kirkland in a turbo Subaru and pointed to Euro-spec oils instead. Others countered that it's fine at 3,000 to 5,000 mile intervals. One member ran it to 5,000 miles in a 1.4-liter turbo Cruze and said the oil analysis showed life left. Another called the criticism "oil snobbery."
On the Ford Raptor Forum, owners have run it since 2020 and mostly describe it as a bargain with no problems after several changes. Nobody there produced a used oil analysis showing a failure.
The pattern is consistent. Owners who stick to the manual's interval report no issues. The doubts come from people running long drains or high-stress turbo engines, who want more margin than the minimum standard.
What it costs
Kirkland usually works out to about $2.70 to $3.75 a quart. Name-brand synthetic at the same store runs about $6.50.
Product and pack | Price seen | Per quart |
|---|---|---|
Kirkland full synthetic, 4 x 5 qt, sale (Slickdeals, April 2025) | $53.99 | $2.70 |
Kirkland full synthetic, 4 x 5 qt, regular (Slickdeals, April 2025) | $70 | $3.50 |
Kirkland full synthetic, 4 x 5 qt, sale (Slickdeals, August 2023) | $63.99 | $3.20 |
Kirkland 12 x 1 qt mixed pack (Jalopnik, April 2026) | $44.99 | $3.75 |
Mobil 1 High Mileage full synthetic, 6 qt at Costco (Jalopnik, April 2026) | $39.49 | $6.58 |
On a car that takes 5 quarts, that's roughly $14 to $19 of Kirkland against about $33 of Mobil 1 per change. Over three changes a year it adds up to about $50.
Two practical costs. You need a Costco membership, and the best price comes in 20-quart cases, so you need shelf space. One Slickdeals commenter also reported jugs leaking at the seam, so check the case before you leave the warehouse.
If you pay a shop for oil changes, the oil is only part of the bill. Our guide to what a car service costs breaks down the labor side.
Who should skip it
Skip Kirkland if your manual names an approval the jug doesn't carry. That's the whole test.
Most European cars fall here. A BMW that calls for Longlife-01 or LL-17 FE, a VW or Audi calling for VW 504 00 or 508 00, or a Mercedes calling for MB 229.5 or 229.71 needs oil licensed to that spec. Costco's listing shows none of them.
Diesels are out too. The jug lists API SP, a gasoline category, and no diesel category like CK-4.
Some Japanese and American manuals also name their own spec on top of API. If yours lists a Ford WSS number or similar, look for that exact number on the bottle. If it's missing, ask the dealer whether API SP alone is accepted for your engine.
Long drains are the gray area. Costco says the oil resists shearing at long intervals but tells you to follow your manual. If your car's oil life monitor regularly pushes past 10,000 miles, an oil with extra approvals gives you more margin.
Does it void your warranty
No, not if it meets the spec in your manual. The FTC's guide to the Magnuson-Moss Warranty Act says a warrantor generally can't require you to use a particular brand to keep your warranty, unless it supplies that item free.
A carmaker can deny a claim if the oil caused the damage. That's why the approval on the label matters. Keep your receipts and note the mileage at each change.
Decision checklist
Use Kirkland if all of these are true:
- Your manual calls for 0W-20, 5W-20 or 5W-30.
- The only specs your manual names are API SP (or older), ILSAC GF-6A (or older) or GM dexos1.
- Your engine is gasoline, not diesel.
- You change oil at or before the interval your manual or oil life monitor sets.
- You have a Costco membership and space for a case.
Buy something else if any of these are true:
- Your manual names a BMW, VW, Mercedes, Porsche or other carmaker approval that isn't on the jug.
- Your manual calls for a grade Kirkland doesn't sell, like 0W-16, 0W-40 or 5W-40.
- You run a diesel.
- You're doing extended drains on a hard-worked turbo engine and want more margin than the minimum standard.
What to do today
- Open your owner's manual to the oil section and write down the grade and every spec it names.
- Compare that list against the jug. Look for the API "donut," the ILSAC starburst and the dexos logo.
- If everything matches, buy the Kirkland grade your manual names. Don't switch grades to match what's on sale.
- Check the case for leaking seams before you leave the store.
- Keep the receipt with your service records in case you ever need to make a warranty claim.
Common questions
Who makes Costco's Kirkland oil?
Highline Warren, formerly Warren Distribution, supplies it, according to Jalopnik. Forum guesses that Amsoil or Mobil blends it have no evidence behind them.
Is Kirkland oil as good as Mobil 1?
For a car that only needs API SP and dexos1 Gen 3, it meets the same standard, and PQIA's tests put hot viscosity and zinc almost level. If your car needs a European carmaker approval, buy whichever oil lists it, because Kirkland doesn't.
Is Kirkland oil the same as Super Tech?
Not confirmed. Owners often say the same company makes both, but nobody has produced proof. Project Farm found the two performed very closely in its tests.
Is Kirkland synthetic oil OK for turbo engines?
Yes, if your manual only asks for API SP or dexos1 Gen 3. Costco says it protects against low-speed pre-ignition, but turbo European engines that need an OEM approval should use an oil licensed to that approval.
Can I top up Kirkland with another brand?
Yes, in the same grade with the same API rating. It's a top-up, not a problem, and you'll be back to one oil at the next change.
How often should I change Kirkland synthetic oil?
At the interval in your owner's manual or your oil life monitor. Costco's own listing says the same. If you're nervous, owners on Bob Is The Oil Guy commonly run it at 5,000 miles or less.
For more on picking and changing oil, see our oils and fluids guides.
Sources
- Costco: Kirkland Signature 5-Quart 0W20 and 5W30 Full Synthetic Motor Oil, 4-pack
- Jalopnik: Who Makes Costco's Kirkland Motor Oil?
- Jalopnik: Does Costco's Kirkland Signature Motor Oil Pass The Same Tests As Other Brands?
- SlashGear: Is Costco's Kirkland Brand Motor Oil Any Good, And Who Makes It?
- Rick's Free Auto Repair Advice: Kirkland Signature Synthetic Motor Oil
- Bob Is The Oil Guy: Who makes Costco oil?
- Bob Is The Oil Guy: Reasons NOT to use Kirkland 0W-20 or 5W-30 Synthetic?
- Ford Raptor Forum: Kirkland Signature Full Synthetic Oil, great value
- Slickdeals: Kirkland Signature 0W-20 Full Synthetic 5-Quart 4-pack, $53.99
- Slickdeals: Kirkland Signature 5W-30 Full Synthetic 5-Quart 4-pack, $63.99
- FTC: Businessperson's Guide to Federal Warranty Law
Featured image: Costco by JeepersMedia, CC BY 2.0. Source
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