Can I Use Diesel Oil in My Gas Engine?

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 5W-30 motor oil that meets the API SN specification, you can safely use a diesel oil of the correct viscosity that meets the API SP spec.

For the typical gasoline application, however, a diesel oil isn’t required and the more appropriate choice is a quality gasoline motor oil for both performance and value.

Diesel trucks

Diesel oils perceived as “tougher”

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.

Find out: What’s the Best Oil for Turbo Cars?

Others lean toward higher-viscosity oils to protect against wear.

Some want to run a 15W-40 oil in their gas engine, and it’s often easier to find a 15W-40 or similar viscosity of 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 Mechanical Engineer – Product Manager, Heavy Duty.

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 specifications for diesel oil (currently CK-4) and its “S” category for gasoline motor oil (currently SP).

Though they’re 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.

AMSOIL diesel oil. conventional vs. synthetic oil
Kenny Hauk Power Wagon | Diesel Oil in gas engine

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 for your gas engine, 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.

AMSOIL Signature Series

Do most gasoline engines need 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.

Want the Best Diesel Oils for Your Vehicle?

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.

Mark Moriarity Collection - Classic Car

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.

Updated. Originally published June 10, 2016.

Comments

  1. So what your saying is…..I don’t have to buy AMSOIL products. I can buy less costly products that have the same rating. Thank you AMSOIL for clarifying this and saving me money.

    1. Hi Bob,

      Yes, you can do that. But remember that industry specifications establish a minimum performance level. We differentiate AMSOIL products by formulating them to deliver protection beyond minimum requirements. We make our products for enthusiasts who want the best, not who settle for minimum performance. For that reason, we’re never going to be the cheapest oil on the shelf. And, honestly, we’re proud of that.

      We understand that some people are fine with minimum performance in their vehicles. If you fall into that camp, then look for the lowest-priced oil that meets the required spec for your engine.

      Thanks for reading,

      John

  2. is there a difference in the formulation of marine oils and auto or diesel land oils? (besides the extra cost) Can they be used interchangibly all other specifications being equal?

    1. Hi Dan,

      Yes, marine oils tend to include a higher concentration of anti-corrosion additives to combat the moisture to which marine engines are exposed. Otherwise rust can form on the cylinders, rings or other components in short order. The rust flakes off and populates the oil, where it circulates in the engine and scours parts like sandpaper. However, you may use, for example, a diesel oil in a marine engine if it meets the appropriate specifications. For best performance, though, we suggest using an oil specifically made for the application in which you plan to use it.

      Thanks,

      John

  3. i have a chevy silverado 2000 with 330k miles or maybe a little more. It calls for 5 30, but have been using 15 40 CK chevron. i was told by a long time mechanic it’s better for my truck since such high mileage. However, i hear my lifters sticking slightly and he said carbon buildup. Not sure I buy that. What should I do since I’ve used that in my motor for over a year, and possibly 300 miles or so (hardly use the truck).

    Don’t want to switch back and forth on things too much and risk issues. Marvel mystery oil, FRAM heavy duty oil filter and which oil you recommend I use based on the above? or any other things I should do to increase engine life and decrease lifters sticking upon warm up.

    Thanks

  4. Hi there, my Hyundai Santa Fe 2 on 13 2.2 turbo diesel has just topped 250,000 klm. Runs and tows great. I have in the past always run full synthetic oils in gas engines, this is my first diesel. Would recommend full synthetics in this engine, and should normal manufacturer specs be adhered to or should I be looking at a heavier grade.

    1. Hi Julian,

      For best protection and performance, use full synthetic oil in your diesel engine. It’ll provide improved wear protection, heat resistance and cleanliness. Follow the specifications given in your owner’s manual regarding viscosity and industry or manufacturer specifications when choosing an oil.

      Thanks,

      John

  5. HDD 5W/30 is my favorite Diesel and gasoline oil for older vehicles. It has the gasoline rating of SL, has high zinc and Phosphorous plus a higher TBN than Z-Rod for classic car engines that sit for lengthy periods of time. If the TBN was increased in Z-Rod I would use it.

    1. Hi Donny,

      How long has it been in the engine? If it’s only been a few days/miles, it’s unlikely you’ve done any lasting harm. Even so, drain the oil and replace it with the correct viscosity.

      John

    1. Hi Chad,

      Your engine calls for 5W-30 motor oil, so it’s best to stick with the recommended viscosity. You can, however, use a 5W-30 diesel oil if it meets the appropriate performance specifications outlined in your owner’s manual.

      Thanks,

      John

  6. What would be a better option for a modern turbocharged engine (no catalytic converter) producing over 100hp per liter: Z-rod or Dominator

    1. Hi Masrul,

      Yes, provided the oil meets the engine’s viscosity requirements and is made for the performance specifications given in your owner’s manual.

      Thanks,

      John

  7. HMMM, this article doesn’t mention anything about the higher ZDDP in diesel oils, which is needed in older engines. I use diesel oil in all my outdoor power equipment for the same reasons. Newer automotive engines had added roller lifters and other things to account for the lack of zinc, but older engines still need it.

    1. Duane, Amsoil has a specific oil for this known as the “Z-Rod” series. No need to use diesel to get that high zinc content.

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