AMSOIL Signature Series

Upgrade My Engine
To Signature Series.

The pro-grade 100% synthetic that's guaranteed for 25,000 miles. Pick your weight and we'll unlock your Preferred Customer program price.

75% More wear protection
25,000 Mile drain interval
-65°F Cold-flow tested

0W-20 Modern gas 5W-30 Best-seller 0W-40 Euro / performance

Show My Price → Read FAQ

● In stock · ships within 1 business day API SP · ILSAC GF-6 · dexos1 Gen 3

AMSOIL Signature Series 5W-30 Synthetic Motor Oil quart

Independent lab-tested performance

Why Signature Series Outperforms Every Quart on the Shelf

Every claim is backed by published results — Sequence IVA, TEOST MHT, and API SP testing.

75%

More Wear Protection

vs. industry standard

25K mi

Guaranteed Drain

or 1 year, whichever first

-65°F

Cold-Flow Tested

starts in extreme cold

50%

More Detergents

superior cleaning power

Shop AMSOIL Signature Series

Pick Your Quart

All three fit the 25,000-mile drain guarantee. Same formula family, different viscosity.

75% more engine protection against horsepower loss and wear1

AMSOIL Signature Series 0W-20 100% Synthetic Motor Oil

Product Code: ASMQT-EA

5.0 (6,629 reviews)

Retail:

Preferred Customer Savings

~25%off retail

Join the Preferred Customer program to save approximately 25% off the retail price

Guaranteed 25,000 / 1 year

SP (Resource Conserving), GF-6A

Free Shipping $100+

Show My Price Full Specs & Tests

National Synthetics is an authorized AMSOIL dealer. Links earn us a commission at no extra cost to you. Full disclosure

75% more engine protection against horsepower loss and wear1

AMSOIL SIGNATURE SERIES 5W-30 100% SYNTHETIC MOTOR OIL

Product Code: ASLQT-EA

5.0 (6,712 reviews)

Retail:

Preferred Customer Savings

~25%off retail

Join the Preferred Customer program to save approximately 25% off the retail price

Free Shipping $100+

Show My Price Full Specs & Tests

National Synthetics is an authorized AMSOIL dealer. Links earn us a commission at no extra cost to you. Full disclosure

75% more engine protection against horsepower loss and wear

AMSOIL Signature Series 0W-40 100% Synthetic Motor Oil

Product Code: AZFQT-EA

5.0 (6,629 reviews)

Retail:

Preferred Customer Savings

~25%off retail

Join the Preferred Customer program to save approximately 25% off the retail price

Guaranteed 25,000 / 1 year

SP, SN PLUS, SN, MS-A0921, MS-12633, MS-10725, MS-10850

Free Shipping $100+

Show My Price Full Specs & Tests

National Synthetics is an authorized AMSOIL dealer. Links earn us a commission at no extra cost to you. Full disclosure

Published spec highlights

From the AMSOIL Product Data Bulletin

Every claim on this page is traceable to AMSOIL Signature Series Product Data Bulletin G2880 and the Sequence IVA, TEOST MHT, and dexos1 Gen 3 LSPI test results published with it.

Sequence IVA wear test

Average cam wear: 20.28 µm (vs. 90 µm industry standard) — 75% better wear protection.

Independent lab, ASTM D6891

GM dexos1 Gen 3 LSPI test

Zero LSPI events across the full GM dexos1 Gen 3 LSPI engine-test sequence — 100% LSPI protection.

Per dexos1 Gen 3 spec

GM Turbo Coking test

Coking-temperature increase of 3.6% (vs. 13% industry standard) — 72% better turbocharger protection.

GM Turbo Coking method

Frequently Asked

Straight Answers From Your Dealer

Is AMSOIL Signature Series really guaranteed for 25,000 miles?

Yes — Signature Series is guaranteed for 25,000 miles or 1 year in normal service, whichever comes first. For severe service (towing, dusty conditions, frequent short trips), change at 15,000 miles or 1 year, or at the OEM interval if it's longer.

Will using Signature Series void my new-car warranty?

No. Signature Series meets or exceeds the manufacturer specifications for gasoline engines requiring API SP, ILSAC GF-6A/B, dexos1 Gen 3, Ford WSS-M2C961-A1 and more. The Magnuson-Moss Warranty Act protects your warranty when using an aftermarket oil that meets those specs.

Which viscosity do I need — 0W-20, 5W-30, or 0W-40?

Check your owner's manual. 0W-20 is the common modern fill for most late-model gas engines; 5W-30 is AMSOIL's best-selling grade and fits most domestic V6/V8 applications; 0W-40 covers high-performance and European fills (BMW LL-01, MB 229.5, Porsche A40, VW 502.00).

How much can I save as a Preferred Customer?

Preferred Customers save up to 25% off the catalog retail price. Membership is $20/year — or free with any order of $100 or more. One order typically pays the membership off several times over.

Is Signature Series compatible with other motor oils?

Yes. It's fully compatible with conventional and other synthetic oils, but mixing reduces the performance benefits and shortens service life. AMSOIL does not support the 25,000-mile drain interval when oils have been mixed.

Keep reading