Why Did We Reformulate Signature Series Synthetic Motor Oil?

Simply put, we reformulated Signature Series Synthetic Motor Oil to solve problems.

For all the derision heaped upon the internal-combustion engine, it remains our primary mode of propulsion. And, despite the gains of hybrids and electric vehicles, it will remain so for the foreseeable future.

One reason is the tremendous efficiency gains gas and diesel burners have made since the 1970s. The loud, proud cast-iron powerplants of yesteryear may still quicken your pulse when they roar past powering a hot rod or classic car, but they can’t match the fuel economy and reduced emissions of the engine likely powering the vehicle you drove to work today.

That’s due to the widespread use of turbochargers, direct fuel injection, variable valve timing and lightweight materials.

But, despite their many benefits, modern engines present several challenges, and it’s up to the motor oil to solve them.

Four little letters, one big problem

One of the biggest is low-speed pre-ignition (LSPI). If you read the AMSOIL blog, you’ve heard about LSPI by now. LSPI is such a big deal that it’s the driving force behind the next generation of motor oil performance specifications.

In a nutshell, LSPI is the spontaneous ignition of the fuel/air mixture prior to spark-triggered ignition. It occurs in modern turbocharged, gasoline-direct-injection (T-GDI) engines, and it’s another version of pre-ignition, which has been around since engines were invented. In this case, though, it occurs under low-speed, high-torque conditions and is much more destructive than typical pre-ignition.

low speed pre ignition - Signature Series Synthetic Motor Oil

Computers to the rescue

Automakers can program their vehicles to avoid operating conditions that invite LSPI. The problem, though, is that programming the engine to operate on that “ragged edge” that invites LSPI promises fuel economy gains of up to 10 percent.

With CAFÉ standards looming, automakers are eager to realize those efficiency gains.

But they can’t until motor oils hit the market that help prevent LSPI. Motor oil formulation plays a big role in fighting LSPI, so much so that the next generation of motor oil specifications requires oils to pass an LSPI test. The forthcoming API SP and ILSAC GF-6 specifications aren’t scheduled for introduction until fall 2019, however.

Some automakers have grown impatient and have requested that the API, which licenses ILSAC GF-5, supplement the current specification with an LSPI test requirement. That could happen as early as January, 2018.

General Motors is ahead of the game. Its proprietary dexos1® Gen 2 spec, introduced in August, includes an LSPI test.

An oil that solves problems

Which brings us back to Signature Series. We want our flagship motor oil to stand alone as the best motor oil in the world, and preventing LSPI is one prerequisite to achieving that goal.

So we subjected it to an LSPI engine test.

The result? Signature Series Synthetic Motor Oil provided 100 percent protection against LSPI* in the engine test required by the GM dexos1 Gen 2 specification.

In short, the oil solves a major problem plaguing the industry right now.

But wait, there’s more…

What about the old standbys, like engine wear and extreme heat?

Here, too, Signature Series excels.

From the day your engine fires to life, friction tries to wear away bearing surfaces, cylinders, piston rings and other components. Left unchecked, it’ll render your pride and joy a gutless, wheezing shadow of its former self. Eventually, something can break completely.

We formulated Signature Series to deliver next-level wear protection. But we know you want proof, not promises.

In the API Sequence IV-A Engine Wear Test required for the API SN specification, Signature Series delivered 75 percent more wear protection than required**.

What does that mean for you?

An engine that lasts for years and delivers maximum horsepower long after you’ve made the final payment. To prove it, we installed Signature Series 5W-30 Synthetic Motor Oil in a Ford F-150 with a new 3.5L Ecoboost engine to test its ability to protect turbocharged direct-injection engines from torque and horsepower loss during extended drain intervals up to 25,000 miles. Power sweeps were done at the beginning and end of the test to evaluate horsepower and torque retention. As the graph shows, Signature Series helped maintain engine performance throughout the 100,000-mile test.

ford f150 3.5 ecoboost dyno sheet - Signature Series Synthetic Motor Oil

Fights engine deposits

Engine deposits, too, do their best to sideline your vehicle. High heat can breakdown motor oil, leading to piston ring, piston crown or valve deposits, which erode horsepower and efficiency. In severe cases, your engine can fail altogether.

Heat is more prevalent in T-GDI engines. Turbos run on exhaust gases that can exceed 1,000ºF and can spin more than 150,000 rpm. The turbo’s center section contains an oil-lubricated bearing. The tremendous heat and stress turbos create can cause some oils to break down and form harmful bearing deposits, known as turbo coking. Over time, turbos can suffer reduced performance, or fail completely.

Again, Signature Series solves the problem of extreme heat. We challenged Signature Series to the GM Turbo Coking Test, which consists of 2,000 cycles of extreme heat soaks. An oil must limit the temperature change within the turbocharger to 13 percent or less to pass the test. Signature Series limited the temperature increase to only 3.6 percent, protecting the turbocharger 72 percent better*** than required by the GM dexos1® Gen 2 specification.

turbo compressor wheel and shaft
Signature Series controlled heat and minimized performance-robbing deposits on the turbo bearing and shaft surfaces.

And, lest we forget, the performance of Signature Series Synthetic Motor Oil lets you extend drain intervals to 25,000 miles/one year if you choose, even in turbocharged engines.

With challenges to engine protection and performance mounting – and new problems cropping up – it’s vital we stay one step ahead.

That’ll help you continue to get the best protection and most years out of your vehicles.


* Based on independent testing of AMSOIL Signature Series 5W-30 motor oil, in the LSPI engine test as required for the GM dexos 1® Gen 2 specification.
** Based on independent testing of AMSOIL Signature Series 0W-20, in ASTM D6891 as required by the API SN specification.
*** Based on independent testing of AMSOIL Signature Series 5W-30 in the GM turbo coking test.



  1. My question is …will the Signature series 5w 50 oil new labels carry the API “donut” logo in the future….I have a Shelby GT350 and I know the 5w 50 series meets Ford Spec for this engine but having that API “donut” on the bottle would give 100% piece of mind for any major warranty issues pertaining to the engine such that Ford cannot come back and deny a claim due to this



    1. Hi Jack,

      For the most thorough answer, see the “API Licensing” section on our FAQ page.

      In essence, however, the answer is no, Signature Series won’t feature the API “donut” on its label. API licensing was originally designed for petroleum oils, not synthetic. Submitting our Signature Series formulation for API licensing would limit our ability to continually improve the formulation with new technologies. It’d increase the price of the product, too. The API sets minimum performance requirements an oil must meet to include the donut on its label. Signature Series is designed to exceed minimum requirements. It’s recommended for the leading performance and manufacturer specifications, including the forthcoming API SP and ILSAC GF-6 specs that aren’t even out yet.

      As for your warranty, Ford cannot deny your factory warranty based on your brand of oil or whether it has the API donut on its label. The federal Magnuson Moss Warranty Act requires that companies prove the oil caused a problem. In addition, we also protect you with our Limited Liability Warranty.

      You have one sweet ride; protect it with the best by using Signature Series.



  2. I would strongly advise anyone that is looking to do extended drain intervals to do UOA testing to establish the safe limit for your application. While Amsoil Signature Series is amazing and I have been using it for over a decade there is a lot of problems with modern engines adding excessive fuel to the oil like the Honda 1.5T, Turbo & Direct Injected engines and even plain Jane vehicles like Caravans that are short-tripped a lot. For me that does mainly highway miles I can get extended intervals, for others in my family they can’t get anywhere near the 25,000 mile OCI or even the 15,000 mile OCI before the lab condemns the oil due to fuel dilution. This isn’t a fault of Amsoil it’s a fault of the conditions placed upon it and any oil would fail. In my opinion in these circumstances you can run XL for a shorter duration and it’s still a fantastic oil at a more economical price or step down to OE which is still a great oil just built for shorter intervals. I wouldn’t run anything but Amsoil oil or ATF’s in my applications because I have a decade of proof they are superior but do it wisely. If you google RockAuto Wix 24077 you can get Wix $10 USD UOA kits to check on your oil. It’s cheap insurance you are using a safe oil change interval. Happy motoring all!

    1. Hi Steve,

      That’s great advice. We recommend Oil Analyzers INC. for used oil analysis. They have a wealth of experience analyzing AMSOIL synthetic motor oils and other lubricants.



  3. Hey,

    Will the SS line still meet the specs via Chrysler/Dodge/ex. Via Hellcat, SRT, Vipers-Ms-12633? I’d like to use the SS over pennzoil.

  4. John,

    I’ve been using Amsoil products for years now on all my other Naturally Aspirated cars and lawn equiment.

    However, I recently bought a 2018 Chevy Equinox with the 2.0L Turbo LTG engine and I do want to use your products in it, but I need to be sure I’m using your latest formula (dexos1 GEN 2 standards).

    How can I be sure I’m ordering the new Signature Series formula (which address Low-Speed Pre-Ignition) and not the old version? I’m specifically interested in SS 0W/30 and 5W/30, Product Codes: AZO & ASL.

    Will there be any new designation (or Product Code) on the bottle label that I should look for?

    1. Hi Joe,

      If you order Signature Series today, you’re guaranteed to get the new formulation that’s recommended for dexos1 Gen 2. If you’re buying retail or from an AMSOIL Dealer, look for the “75% More Wear Protection” banner across the front of the product label. You can see an example on the homepage of our website.

      Thanks for reading.

  5. JOHN

  6. Hi John,I just looked at the Signature Series data bulletin for the new formulations. Under severe service,it also looks like Direct Injected engines were removed in addition to Turbocharged engines.Thats is interesting,I would love to see someone post a uoa on the new formula in one of of both of those conditions.

    I was using Mobil 1 AFE 0W30 in our non turbo DI engine. On my longest oci of 6490 miles,I had 3.1% dilution in addition to adding 18 oz. during that interval. I switched to Amsoil SS 0W30 because I knew it was their premier oil and is rated for better mpg,even over their xxW20 oils which most do not know.

    With over 10,000 hand calculated miles tracked,believe it or not,we picked up a solid 2 mpg better than Mobil’s AFE formula with zero usage on better than 50% more mileage. I will be ordering the new SS 10W30 in a week or so.I will probably give up some or all of the mpg,but,I want it for its super low noack volatility numbers which should do well over time in any DI engine.

  7. The article says you can run Signature Series for 25,000 miles on a turbocharged engine. This oil,on any turbocharged or Direct Injected engine should be used as severe service and run to 15,000 miles max. I have a non-turbo Direct Injected engine using Signature Series 0W30.oil. Polaris just analyzed the oil at 9500 miles of use in non severe service conditions where the TBN dropped to 3.0 from a starting TBN of 12.6. The oil is still serviceable,but,it will not make it to 25,000 miles. Use caution and common sense.

    1. Hi John,

      Yes, that’s right – you can run Signature Series to 25,000 miles/one year in a turbocharged engine if you want. We recently revised our Severe Service definition to remove turbos based on results of testing we performed. That being the case, you obviously know what you’re doing, so stick with what’s working for you.

      Thanks for reading.

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