What oil does my car take?

Your owner's manual lists the exact viscosity grade and API specification your engine requires — typically something like '5W-30, API SP, ILSAC GF-6A.' The oil filler cap itself often has the viscosity printed on top. Using the wrong grade can reduce fuel economy, cause premature wear, or in some turbo engines, trigger timing chain problems. When in doubt, match the manual exactly.

Is full synthetic worth the extra cost?

For the vast majority of modern vehicles, yes. Full synthetic provides better cold-start protection, handles extreme temperatures without breaking down, and safely extends change intervals to 7,500 to 10,000 miles. That longer interval offsets most of the extra cost per quart. Many vehicles built after 2012 require synthetic oil to meet manufacturer specifications regardless of preference.

Can I switch from conventional to synthetic?

Yes, at any time, on any engine. The old myth that synthetic oil causes seals to leak in older engines is largely outdated — modern synthetic formulations are fully compatible with every seal material in common use. Switch at your next oil change with no special prep. On very high-mileage engines that have never seen synthetic, use a high-mileage synthetic blend for the first change to ease the transition.

Best Motor Oil for Your Car: How to Choose (2026 Guide)

Motor oil is the most important $30 purchase you make for your car. It's also the place where shops and dealers extract the widest margins, and where a little knowledge saves you hundreds per year. This guide strips the marketing language off the topic and tells you exactly what to put in your engine — and what to skip.

What the Numbers Mean: 5W-30, 0W-20, and the Rest

Every motor oil label carries a viscosity rating like 5W-30 or 0W-20. These numbers describe how thick (or thin) the oil is at two temperatures. The number before the W is the cold viscosity — lower numbers flow better at startup in cold weather. The number after is the operating viscosity at full engine temperature. 5W-30 is thinner when cold than 10W-30 but the same thickness at operating temp.

Your engine was designed for a specific viscosity, and deviating from it has consequences. Going too thin (e.g., running 0W-20 where 5W-30 is specified) can reduce oil film strength and increase wear. Going too thick (running 10W-40 where 0W-20 is specified) can restrict flow to tight tolerance passages, especially in modern engines with variable valve timing. Match the manual.

Conventional vs Synthetic Blend vs Full Synthetic

Conventional oilis refined from crude oil with additives. It's cheap ($4 to $7 per quart) but breaks down faster under heat and shear. Appropriate for older, simpler engines that specified conventional when new — think pre-2005 trucks and economy cars.

Synthetic blend mixes conventional base oil with some synthetic base stock. Costs $6 to $9 per quart. Offers modestly better protection than conventional but nothing like full synthetic. It exists mostly as a marketing tier between the two.

Full synthetic ($8 to $12 per quart) is engineered from the molecule up for consistent performance across temperature extremes. It handles heat, cold, and long intervals far better than conventional. If your car was built after 2010, odds are full synthetic is either required or strongly recommended.

High-Mileage Oil: When and Why

High-mileage formulations include seal conditioners designed to swell aging rubber gaskets slightly, reducing small leaks and oil consumption in engines with 75,000+ miles. If your car is burning a half-quart between changes, leaving small spots on the driveway, or was previously maintained with long change intervals, a high-mileage synthetic (our pick on Amazon) is a smart, cheap countermeasure.

The caveat: high-mileage oils don't fix actual leaks. If you see a growing puddle under the car or the oil level drops significantly between changes, that's a seal or gasket failure that needs shop attention.

What Your Manual Actually Specifies

Open the owner's manual to the lubricants section. You'll see three pieces of information: viscosity (e.g., 5W-30), API/ILSAC specification (e.g., API SP, ILSAC GF-6A), and sometimes a manufacturer-specific approval (BMW LL-01, VW 502.00, Mercedes 229.5, etc.). Those last approvals matter on European vehicles and some performance engines — they certify the oil meets specific chemistry requirements, not just the viscosity grade. Oil that says "suitable for use where X is required" is not the same as oil that's officially approved by X.

Don't deviate from the manual without a reason. The "performance" grades and exotic specifications some shops try to upsell rarely benefit the average driver.

API and ILSAC Ratings: SP and GF-6A Are the Current Standards

API (American Petroleum Institute) and ILSAC (International Lubricant Standardization and Approval Committee) set the performance standards for motor oil. API SP is the current gasoline engine standard, and ILSAC GF-6A/GF-6B are the current passenger-car categories. Oils carrying these marks have been tested for wear protection, sludge resistance, fuel economy, and (critically for modern turbo engines) LSPI prevention (low-speed pre-ignition). If an oil doesn't carry the current API/ILSAC marks, don't buy it.

Top Brand Recommendations by Category

Mobil 1 Extended Performance— the benchmark full synthetic for most drivers. Widely available, OEM-approved across nearly every major automaker, and reliably consistent from bottle to bottle. (Check price on Amazon)

Valvoline Advanced Full Synthetic— slightly cheaper than Mobil 1 in most markets with comparable additive chemistry. A strong value pick for daily drivers. (Check price on Amazon)

Castrol Edge— the go-to choice for many European vehicle specifications. Strong performance under sustained high-RPM use. (Check price on Amazon)

Pennzoil Platinum— made from natural gas (gas-to-liquid base stock) rather than crude. Runs cleaner and leaves less deposit buildup over time. Popular among owners of direct-injection engines. (Check price on Amazon)

Shell Rotella T6— a diesel-rated synthetic that's also a cult favorite for high-performance gas engines and older vehicles that benefit from higher zinc content. Specifically designed for diesel use — not appropriate for modern gas cars that require API SP. (Check price on Amazon)

Amsoil Signature Series— premium direct-to-consumer synthetic with extended drain intervals (marketed for 15,000+ miles between changes). More expensive per quart but appeals to enthusiasts who value the additive package. (Check price on Amazon)

Budget pick: Store-brand synthetic— Walmart's SuperTech, Costco's Kirkland, and Amazon Basics full synthetics all carry the same API SP / ILSAC GF-6A certifications as the name brands, typically at 25 to 40 percent less per quart. If the label carries the current API mark, the oil meets the same performance standard. (Check price on Amazon)

How Often to Change

For conventional oil, every 3,000 to 5,000 miles or per the manufacturer's time-based interval. For full synthetic, every 7,500 to 10,000 miles on most modern engines — some manufacturers approve up to 15,000 miles with their manufacturer-approved oil. Follow the oil life monitor on newer vehicles; it actually calculates remaining oil life based on driving conditions rather than pure mileage. For the full cost breakdown on each service level, see our oil change cost guide.

Red Flags at the Dealer

A dealer charging $110 for a 5-quart synthetic oil change on a Camry is overcharging by $30 to $50. A dealer "recommending" a higher viscosity than your manual specifies (common: pushing 5W-30 where 0W-20 is required) is guessing or protecting its service margin — don't let them. An "engine flush" added at the oil change is almost never justified and can actually release sludge into oil passages.

The fix is to either bring your own oil to a friendly independent shop (many will install customer-supplied oil at a labor-only rate) or learn to do the job yourself. Our guide on doing your own oil change walks through whether DIY is right for your situation. And if you're looking to understand the bigger maintenance picture, our maintenance schedule guide slots oil changes into the broader service rhythm.

Pick a quality synthetic that meets your manual's specification, stick with it, change on schedule. That's the entire motor oil strategy. Everything beyond that is upsell.