Last verified: August 2026.
Two numbers decide what goes in your crankcase: the viscosity grade your manufacturer specified, and how many quarts the engine holds. Everything else on the shelf, the brand, the base oil marketing, the price per quart, is a conversation you can only have once those two numbers are settled. This page is a reference for finding them, reading the certification marks that tell you whether a jug actually qualifies, and understanding what the current API and ILSAC standards changed. There are no rankings here and no picks.
Three places your car's oil spec is written
The owner's manual
The manual is the source of truth, and two sections in it matter. The maintenance or lubrication section names the viscosity grade plus the specification the oil has to meet, often as a chart of grades plotted against outside temperature. The capacities table, sometimes labeled fluids or refill capacities, gives the quarts.
Many manuals list a primary grade and one or more alternates approved for hot or cold climates. Those alternates are real approvals, not suggestions someone made up, and a manufacturer that sanctions 5W-30 above a certain ambient temperature has tested that combination. Nearly every automaker now hosts free manual PDFs on its owner portal, so a missing glovebox copy is a five-minute problem.
Read the whole entry, not just the grade. Manuals routinely name two requirements in the same sentence: a viscosity grade and a specification the oil has to satisfy, such as API SP, ILSAC GF-6A or newer, dexos1 Gen 3, or an approval number from a European automaker. Those are separate tests. A 5W-30 that is not licensed to the named specification satisfies half of what the manual asked for, and a licensed oil in the wrong grade satisfies the other half.
The oil filler cap
Most cars built in the last two decades carry the grade molded or printed into the plastic oil filler cap on top of the engine. It reads plainly: 0W-20, 5W-30, sometimes with a specification name like dexos1 or API SP alongside it. It takes ten seconds to check and it is right the overwhelming majority of the time.
The cap has two limits. It reflects what the engine shipped with, so if the manufacturer revised its recommendation in a later service bulletin the cap will not know about it. And the cap only ever gives you the grade, never the capacity.
The fitment lookup
The third path is a lookup that already did the manual reading for you. CarCareTruth maintains one at the engine oil lookup, covering more than 1,000 vehicle generations back to 1990.
How the CarCareTruth engine oil lookup works
Pick a year, make, and model and the tool returns the recommended viscosity grade, the oil capacity in quarts, and whether that capacity figure counts a fresh filter. Two rules govern what it shows.
First, a grade or capacity is labeled confirmed only when two independent sources agree: the OEM owner's manual plus a genuinely separate witness. Where that bar has not been cleared, the page says so and hands you the manual-and-cap method instead of bluffing a number. Second, every capacity is labeled with or without a filter, because those two figures differ by roughly half a quart on most engines and that gap is enough to read as overfilled on a dipstick.
Nothing in that lookup is a brand call. A viscosity grade and a capacity are physical facts about an engine, decided by the people who designed the oil pump and the bearing clearances. Which jug you pour is a separate question with a separate answer.
What the numbers on the bottle mean
The grades themselves come from SAE J300, the Society of Automotive Engineers standard that defines engine oil viscosity classifications. J300 is explicit that it classifies oils in rheological terms only, meaning purely by how the oil flows. A grade tells you nothing about quality, additive content, or how long the oil lasts. Two 5W-30 oils can differ enormously and still both be honestly labeled 5W-30.
The W stands for Winter, not weight. The number in front of it describes cold behavior: how easily the oil turns over in a frozen engine and how readily it gets pumped to the top end before the bearings run dry. The number after the dash describes the oil hot, at engine operating temperature.
This is why 0W-20 and 5W-20 are the same grade where it counts most. Both are 20-grade oils and behave identically once the engine is warm. The 0W simply flows better on a cold morning, which is the reason manufacturers chasing cold-start wear and fuel economy specify it.
The cold half is also two tests
The winter number is not a single measurement either. J300 sets a limit on how hard the oil is to crank at a defined low temperature, and a separate limit on how readily the oil pump can move it before the pump loses its prime. Each winter grade has its own pair of temperatures, and they get colder as the number gets smaller.
The practical version: a lower winter number buys you protection in the first thirty seconds after a cold start, which is the window where most measurable engine wear happens. It buys nothing at all once the engine is at temperature. An owner in Phoenix and an owner in Fairbanks running the same 20-grade oil have the same oil in traffic and very different oil in a driveway at 6 a.m.
The second number carries two requirements
The hot half of the grade is two separate specifications wearing one number. The first is a viscosity band at 100°C, which is the ordinary thickness measurement. The second is a minimum film strength under high shear, measured at 150°C, which describes how thick the oil stays in the one place it is being squeezed and torn hardest: the thin gap inside a loaded bearing. The industry calls this high-temperature high-shear viscosity, or HTHS.
That second requirement is where two bottles wearing the same number stop being the same oil. J300 splits the 40 grade in half:
| Grade | Minimum film strength at 150°C (mPa·s) |
|---|---|
| 0W-40, 5W-40, 10W-40 | 2.9 |
| 15W-40, 20W-40, 25W-40 | 3.7 |
Both columns say 40 on the front of the jug. The heavier winter grades are required to hold a meaningfully stronger film in a hot bearing. If a manual specifies 15W-40 for a hardworking engine, swapping in a 5W-40 changes something the label does not advertise.
Reading the bottle: donut, starburst, and shield
Three marks do the certification work, and they are not interchangeable.
The API donut is the round mark, usually on the back label. The top section names the service category, such as API SP or API SQ. The center gives the SAE viscosity grade. The bottom section reads Resource Conserving if the oil qualifies on fuel economy and emissions-system protection.
Per API 1509, only one service category may appear in the donut at a time. A jug displaying two categories in the top ring is not following the licensing rules, which is a reasonable signal to put it back.
The starburst is the round sunburst mark on the front label, and it certifies ILSAC GF-7A. Think of it as the shorthand for "this oil is appropriate for a modern gasoline passenger car," because ILSAC standards are written jointly by American and Japanese automakers for exactly that fleet.
The shield is the newer mark and it certifies ILSAC GF-7B, which applies to one grade only: 0W-16. Cars specified for 0W-16 are a small but growing group, and the separate mark exists so nobody grabs a 0W-16 for an engine that wanted a 20-grade.
The most useful thing these marks tell you is what an oil cannot claim. A 20W-50 can carry the API donut, because API service categories are not grade-restricted. It will never carry the starburst, because ILSAC's passenger-car standard does not include a 50 grade at all. That is not a mark against 20W-50, which has legitimate uses in older and air-cooled engines. It just means the starburst is silent about it.
The current standards: API SQ and ILSAC GF-7A
API SQ and ILSAC GF-7A both became licensable on 2025-03-31. GF-7A replaced GF-6A as the standard the starburst certifies, and GF-7B replaced GF-6B for 0W-16.
API SP was not retired. SQ joined it as an additional category, and SP remains licensable and legal to sell. SQ is backward compatible, so an SQ oil in the correct grade covers an engine whose manual asks for SP or an earlier category. A shelf in 2026 will legitimately hold both, and neither is stale.
GF-7A covers five viscosity grades: 0W-20, 5W-20, 0W-30, 5W-30, and 10W-30. Two changes in the upgrade are the ones worth understanding as an owner:
- An aged-oil test for low-speed pre-ignition. Low-speed pre-ignition is the failure mode where fuel in a small turbocharged engine lights off early and violently enough to crack a piston or snap a rod. GF-6 already tested for it on fresh oil. GF-7 added a test on aged oil, because a formula that suppresses the problem when new and stops doing so at 4,000 miles is not solving anything.
- A tighter timing-chain wear limit. GF-7A holds chain wear to a maximum 0.080 percent increase over the test. Chain stretch throws off valve timing gradually and expensively, and direct-injection engines have been harder on chains than their predecessors.
One caveat about checking API's own site
API's consumer-facing engine oil page still describes API SP and ILSAC GF-6A as the current pairing. An owner who lands there in 2026 gets an answer that was accurate in 2020. The authoritative check is the API EOLCS licensee directory, which lists every marketer and product currently licensed, by category and grade. If a brand claims a license, the directory either confirms it or does not.
Approvals versus self-certification: who actually checked
This is the distinction that separates a real specification claim from marketing copy, and the language on the bottle gives it away.
A label that reads "meets the requirements of" or "recommended for use where X is required" is a self-certification. The oil company is asserting compliance on its own authority. That assertion is frequently true, and plenty of capable oils are sold this way. Nobody independent verified it.
A license or approval is a different animal. The company submitted the formula, an outside program tested it, the result is published in a searchable directory, and the license is renewed on a schedule rather than granted once. API's EOLCS is one such program. GM's dexos is another.
How the GM dexos mark works
For dexos, the licensing evidence is physical and specific. A licensed oil carries the dexos logo on the front label and an 11-digit license number on the back. Both, together. A jug with the logo and no number, or a back-label sentence about meeting dexos requirements with no mark at all, is not a licensed dexos oil. GM publishes the licensed product list, so the number is checkable.
European approvals name the oil, not the category
European manuals typically do not ask for an API category at all. They name an approval: MB 229.5 for Mercedes-Benz, BMW Longlife-01, VW 502.00, Porsche A40. Each of those means the automaker itself ran that specific oil through its own test program and published the result.
That changes what you are shopping for. An API SQ 5W-40 that carries no MB 229.5 approval has not been evaluated against what Mercedes asks for, whatever else is true about it. When a European manual names an approval, the approval is the spec.
Capacity: how many quarts your engine holds
The capacities table in the owner's manual is where this lives, and it usually gives more than one figure per engine. The one to use for a normal oil change is the with-filter capacity, because the filter is replaced at the same time and holds a few ounces of its own. A dry-fill figure, describing a fully drained engine with no oil anywhere, reads higher and is not the number to pour into a car you just drained on a driveway.
Capacities do not follow displacement in any predictable way. A 2.0-liter four can hold anything from 4.4 to 6.0 quarts depending on how the oil pan and cooler circuit are laid out, and two engines in the same family often differ. Guessing from the size of the engine is not a method.
Buying the right amount is the practical consequence. Motor oil sells in 5-quart jugs and single quarts, and a large number of engines take something awkward like 5.7 or 6.9 quarts. Buying one jug for a 6.9-quart engine leaves you two quarts short mid-job, and buying two jugs leaves most of the second one on the shelf, which is fine as long as you know that going in.
Two failure modes sit on either side of the target. Underfilling reduces the amount of oil available to carry heat away and shortens the margin before the pickup starts sucking air on hard cornering. Overfilling lets the spinning crankshaft whip the oil into foam, and foam does not carry pressure the way liquid oil does. The safe habit is to pour a little short of the listed capacity, run the engine briefly, and top up to the dipstick mark.
Handling oil and used oil safely
New motor oil is a low-hazard product for skin contact in a driveway setting. Used motor oil is a different material: combustion byproducts accumulate in it over an oil change interval, and repeated, prolonged skin exposure to used oil is the exposure route that safety data sheets and occupational sources treat as meaningful. Nitrile gloves and washing off splashes handle it.
Used oil is also recyclable nearly everywhere in the United States, and most auto parts retailers accept it free in reasonable household quantities. The full breakdown of what protective gear actually earns its place in home car care, and what is safety-data-sheet boilerplate, lives in the PPE guide for home car care.
What to do once you know your grade
The grade and the capacity settle what the engine needs. Which jug meets it is the next question, and the certification marks above are how you check a candidate: the right grade in the donut center, a current service category above it, the starburst if the grade is one of the five GF-7A covers, and a real license number for any manufacturer specification the manual names.
If you want our ranked picks inside your grade, they live in the motor oil buying guide, scored on certification currency, additive evidence, and what the published safety data says. That page is a separate exercise from this one on purpose. Grade first, brand second, and never the other way around.