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Do’s and Dont’s using Diesel Oil in Gas Engines

Can I Use Diesel Oil in My Gas Engine?

It’s good to familiarize yourself with the topic as there are particular conditions which you may benefit from using diesel oil or perhaps you have a fleet and are looking for one oil for everything, one size fits all.. The short answer: It depends on the brand – the approach to the end user.. Read on.

The simple answer: Yes, you can use diesel oil in a gas engine, provided the diesel oil meets the appropriate specifications and viscosity requirements of your engine.

For example, if your gas engine calls for a motor oil that meets the API SN specification, you can safely use a diesel oil of the correct viscosity that meets the API SN spec. For the typical gasoline application, a diesel oil isn’t required and the more appropriate choice is a quality gasoline motor oil for both performance and value.

The detailed answer: It’s common for some owners of modified gasoline-powered vehicles to favor diesel oils over their gasoline counterparts.

Many assume diesel oils are more durable and more capable of withstanding the increased heat of a powerful, turbocharged engine.

Others lean toward higher-viscosity oils to protect against wear, and it’s sometimes easier to find a 40- or 50-weight diesel oil than a gasoline motor oil. Others favor the increased detergency of diesel oils.

While you can use diesel oil in a gas engine, provided it meets the appropriate specifications and viscosity requirements, there’s far more to the topic than that, as I learned after talking to Mark Nyholm, AMSOIL Technical Product Manager – Heavy Duty.

AMSOIL Sioux Falls Dealer note: Call me if you have any questions on these items. I can help you dial in on the best oil for your particular need. 605-274-2580

Can diesel oil safely be used in gas engines?

Nyholm: It depends on the specifications the diesel oil carries and the recommendation of the original equipment manufacturer (OEM).

The American Petroleum Institute (API) publishes its “C” category of specification for diesel oil (currently CK-4) and its “S” category for gasoline motor oil (currently SN). It’s common for today’s diesel engine oils to carry both the API CK-4 and SN specifications.

Though they’re truly designed for diesel applications, they can be used in gasoline applications for those drivers who want to use one oil in all applications. If the diesel oil carries both specs, feel assured the oil is safe to use in diesel and gas applications. If the diesel oil does not carry the “S” category, I strongly recommend against using it in gasoline applications.

Signature Series Max-Duty Synthetic Diesel Oil 5W-30

Shop AMSOIL Synthetic Diesel Oil

Why do some motorists favor diesel oil over gasoline motor oils?

Nyholm: There are many reasons people choose the oil they use.

Since oil is not top-of-mind with many motorists, it’s typical for people to purchase based on viscosity alone. Many gasoline engines today call for 5W-30, with more and more requiring 5W-20, meaning those viscosities are typically what’s readily available. So, if you’re looking for a 5W-40 or 15W-40, it’s often easiest to find that viscosity in the diesel engine oil aisle.

Others use diesel oil under the assumption it’s a more “heavy-duty” product and must be better than gasoline motor oils.

They may have been told diesel oil is formulated with special components not available in gasoline motor oils, such as more robust detergency additives to handle the soot inherent to diesel engines. In their minds, diesel oils are analogous to better protection.

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Do most gasoline engines really need some of the additives in most diesel oils?

Nyholm: Diesel and gasoline oils are formulated with a variety of additives that improve wear protection, corrosion protection, resistance to foaming, viscosity retention and more. Whether the application is gasoline-powered or diesel-powered, many of the same additives are used based on what we are asking them to do in the formulation.

Now, there are additives designed to manage the byproducts of combustion, and some of those byproducts change, depending on whether you’re burning gasoline or diesel. If you’re running a gasoline engine, it’s best to use an oil that contains the correct additives to handle the byproducts of gasoline combustion. The same holds if you’re operating a diesel engine.

When should someone use diesel oil in their gas engine?

Nyholm: If your gasoline engine is heavily modified to put out more horsepower, using a diesel oil can be beneficial. It’s likely modified engines will need a higher viscosity to withstand the increased stress. You can turn to diesel engine oils for those needs or you might want to consider a racing oil, depending on your engine modifications and lubrication requirements.

Many times the engine builder will help provide insight as to what success they have found. Outside of that, if you have a bone-stock gasoline-powered application it’s best to stick with a gasoline motor oil.

They are designed for that type of application and have the components required to manage that engine. Sure, you can run a diesel oil in a gasoline engine; however it’s likely the formula has additional components your gasoline application doesn’t require, which might end up costing you more money.

AMSOIL formulates a complete line of gasoline and diesel oils for nearly anything you have. They’re dialed in to deliver outstanding protection for their intended applications. Consult the AMSOIL product guides for recommendations for your vehicle.

Find AMSOIL Products for Your Vehicle

Synthetic Warehouse Note: Mark forgot to mention in this last section a popular need for diesel in gas engines are customers who want one oil for their business or fleet.  AMSOIL has products marketed for one size fits all. One popular is our first product which is excellent for RV’s motorcycles and fleets – It’s a 10W-40 that flows nicely and great for anything pre 1999. Check out the AMO 10W-40.

Another is a 5W-30 which makes a lot of sense and is in the newer Signature Series Diesel line – the DHD 5W-30 which is great for the latest API specifications, classics, Ford diesels, cars, mowers and equipment. Excellent for golf courses.

Why Did We Reformulate Signature Series Synthetic Motor Oil?

Why Did We Reformulate Signature Series Synthetic Motor Oil?

Local Sioux Falls note: We are reposing this article from last fall as it is important to realize the changes coming and how these enhancements will only add to the performance on older vehicles too.

AMSOIL’s Signature Series likely already exceeds the future API specification which hasn’t rolled out yet and we know other larger competing lubricant companies are having issues with LSPI (read more below).

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.

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.

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.

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.

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* 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.