A reader asks: I have just changed oil in my car and I’m now going away for five months. The car will be in storage for that time. Do I need to change the oil again after the five-month storage period? The oil used was AMSOIL Signature Series 5W-20.

Our answer: No, there would be no need to change the oil after this storage period. Signature Series has an exceptionally high capacity to fight acids. As it is a premium, long-life motor oil, your engine would be protected during and after storage.

After you remove the car from storage, do not push Signature Series beyond its recommended one-year service interval (or the 25,000 mile limit, whichever comes first). The limit would be one year from the day your oil was changed.

When using lesser motor oil brands, change the oil slightly earlier than normal after storage. The motor oil is fighting acids and degrading during storage.

Change oil prior to storage, rather than after. It is best to drain the acids and combustion by-products held in the motor oil before storage. Installing new motor oil with fresh acid-fighting capabilities is the best course of action.

Bonus Tip

Before storing your car, fill the fuel tank completely so that there is no space for condensation to form. During the fill-up, add a fuel stabilizer (like AMSOIL Gasoline Stabilizer) to prevent fuel degradation and injector (or carburetor) deposits during the months in storage. This will allow for perfect performance after you put the car back into service.

AMSOIL XL 5W-20 Synthetic Motor OilAMSOIL has reformulated their XL Synthetic Motor Oil Series in anticipation of the upcoming ILSAC GF-6 industry specification. The result is long service life, better cleaning power and improved resistance to extreme heat. XL Motor Oil is available in 0W-20, 5W-20, 5W-30, 10W-30 and 10W-40.

Here are the top five highlights of the new rendition of AMSOIL XL Synthetic Motor Oil.

1. Longer Service Life

The service life of the XL Synthetic Motor Oil line was previously 10,000 miles (16,000 km) or 6 months (whichever came first). The new formula boosts the service life to 12,000 miles (19,000 km) or one year (whichever comes first).

2. Improved Turbo and GDI Service

Auto manufacturers are constantly striving to improve fuel economy. In some models they opt for smaller engines. In order to keep performance at acceptable levels (and further improve efficiency), turbochargers and gasoline direct injection (GDI) have been employed. These two technologies bring special challenges to motor oil.

GDI engines can be prone to motor oil-related engine deposits. These deposits can lead pre-ignition and even engine damage. XL Motor Oils are completely immune to deposits in gasoline direct injection engines. Turbochargers can bake oil into hard deposits. XL Series is highly resistant to turbocharger heat and provides dependable turbo protection.

3. Holds Its Viscosity Under Extreme Heat

One of the most impressive attributes of the new version of AMSOIL XL Synthetics Oil is its ability with resist thickening after exposure to hot operating conditions. XL’s strong resistance to both thickening and shearing down is one of the main reasons that AMSOIL was able to safely stretch its service interval out to 12,000 miles or one year.

4. Powerful Deposit Resistance And Acid Fighting Strength

Another reason that AMSOIL was able to increase the oil change interval for XL Series is its upgraded ability to resist the formation of engine deposits.  AMSOIL XL keeps engines clean with powerful detergents. Clean engines run more efficiently and perform at their best.

AMSOIL was also able to boost the total base number (TBN) of XL Series to 10.0. This gives XL a greater capacity to fight acids over long service intervals. This is another layer of engine protection and further reason to have confidence in this product.

5. Price Remains Unchanged

Despite all of these upgrades, AMSOIL is not raising the price of XL Series. The new XL Series did not require more expensive ingredients, it was more a triumph of engineering. XL Series users can reap the benefits of AMSOIL’s 45 years of experience designing the world’s finest synthetic motor oils.


We are quite excited about the new 12,000 mile/ one year drain interval of XL Series. This longer interval is likely conservative considering how AMSOIL products perform in the real world. AMSOIL has a tendency to under-sell and over-deliver.

Would you like to see pricing on the new and improved AMSOIL XL Synthetic Motor Oil Series? Contact us using the form on this page or call us at 1-800-748-5781.

AMSOIL Signature Series 5W-20 Synthetic Motor OilAMSOIL has reformulated their flagship Signature Series Synthetic Oils and the company is quite excited with the results. AMSOIL is touting Signature Series as the undisputed world’s best motor oil.

What Is Signature Series?

Signature Series is AMSOIL’s most advanced line of synthetic motor oils for automotive applications with gasoline engines.

Signature Series is available in the following grades:

Why Did AMSOIL Reformulate Signature Series?

AMSOIL reformulated the Signature Series line in preparation for the new ILSAC GF-6 motor oil specification. This new industry specification will be introduced sometime in spring 2018.
The ILSAC GF-6 standard will address modern motor oil issues such as fuel economy improvement and the ability to perform well in turbo and gasoline direct injection (GDI) engines.

What Are The Benefits Of New Signature Series?

Once the new formula was finalized and tested, even AMSOIL was astonished at the finished product. Terms like “over-engineered”, “exotic” and “world’s best” were used to describe what was previously a very formidable product.

The upshot of the improvements were durability, cleaning ability and powerful heat resistance.

The latest rendition of Signature Series resists thickening, even after being exposed to extreme heat and long service intervals. AMSOIL boasts that the viscosity of Signature Series will be roughly the same after 25,000 miles of service as the day it was poured into the engine.

As for cleaning capability, AMSOIL offers that Signature Series has 50 per cent more cleaning properties than their OE Synthetic Series. As the OE Synthetic Series is a pretty good product in its own right, this is impressive. AMSOIL claims that there likely isn’t a motor oil made that would match the Signature Series cleaning power.

New Signature Series Test Data

AMSOIL performed extensive testing on the new Signature Series formula and the results were very impressive. Here are the highlights.

Engine Wear Testing

Signature Series 0W-20 (the lightest grade) was subjected to the Sequence IVA test. In this test, an engine alternates between 50 minutes of idling and 10 minutes of high RPM operation for 100 hours. This simulates conditions that can create excessive wear. Upon completion of the test, the camshaft was removed and measured for wear in 84 places. Signature Series showed 75 per cent less wear than required by the API SN specification.

AMSOIL Signature Series Cam Wear Graph

Low-Speed Pre-Ignition Test

Many of today’s engines employ gasoline direct injection (GDI) systems. GDI engines can be prone to oil-related deposits. Deposits can cause low-speed pre-ignition (LSPI). This type of pre-ignition can cause poor operation and engine damage. Using the General Motors LSPI testing protocol, the new AMSOIL Signature Series formula provided 100% prevention against this issue.

Turbocharger Protection Testing

Turbochargers are back and more popular than ever. Hot turbos are notorious for being very hard on motor oil. AMSOIL put new Signature Series through the GM Turbo Coking Test. In this test, the motor oil is put through 2000 cycles of extreme heat soaks. To pass this test, the temperature within the turbo must not rise beyond 13 per cent. New Signature Series kept the temperature increase at just 3.6 per cent. This was 72 per cent better than the minimum requirement for the GM dexos 2 Gen 2 specification.

Astonishing Horsepower Preservation

This was our favorite and most telling “real world” test. AMSOIL installed the new Signature Series 5W-30 in a Ford F-150 with the turbocharged 3.5L Ecoboost engine. They measured the horsepower and torque output at the beginning of the test and then ran the truck for 100,000 miles (160,000 km). Oil was changed at 25,000 mile intervals. At the conclusion of the test, the engine was tested on the dynamometer again. As the chart below shows, horsepower and torque output remained all but unchanged. This is testament to AMSOIL’s extraordinary wear control.

AMSOIL Signature Series Horsepower Graph

Resistance To Viscosity Increase Test

The idea behind the Sequence IIV Test is to determine how well an engine oil resists thickening when exposed to extreme heat. AMSOIL Signature Series 5W-30 was installed in a test Chrysler 3.6L Pentastar engine. The test is then conducted with oil temperatures steady at 304°F. This is 100°F above normal oil temperatures. Signature Series thickened by just 6 per cent in this difficult test. The passing grade in this is to keep thickening under 150 per cent.

AMSOIL Signature Series Viscosity Increase Graph

Volatility Resistance Test

This test measures how well a motor oil can resist oil burn-off. In the NOACK Volatility Test, a motor oil is exposed to very hot airflow set at 482°F for one hour. The oil is then tested to determine how much oil had burned off. New AMSOIL Signature Series 5W-20 lost just 5.8 per cent of its volume in this torture test. The API SN limit is 15 per cent.

Remarkable Cold-Cranking Ability

Receiving fast oil flow in cold weather is vital to prevent engine wear at start up. Each of the new AMSOIL Signature Series Synthetic Motor Oils boast spectacular cold-pour-point numbers. This is the temperature where an engine oil stops flowing.

  • 0W-20 -53°C (-63°F)
  • 5W-20 -50°C (-58°F)
  • 0W-30 -50°C (-58°F)
  • 5W-30 -50°C (-58°F)
  • 10W-30 -47°C (-52°F)
  • 0W-40 -50°C (-58°F)
  • 5W-50 -48°C (-54°F)

Will the Signature Series Price Change?

No, the price of the latest Signature Series product line will not change. AMSOIL is suggesting that a higher volume of expensive ingredients was not required. What was more important was a strong commitment to research and development. AMSOIL has been formulating synthetic oils for 45 years and the new Signature Series line is the culmination of that legacy. AMSOIL customers can enjoy the dividends of this vast experience at a very reasonable price.

Where Can I Buy The New AMSOIL Signature Series Synthetic Oils?

We can sell AMSOIL Signature Series at wholesale prices. Request a price list using the contact form on this page or call us at 1-800-748-5781. We ship from 2 warehouses in Canada and 11 in the United States.