What Octane Is Marine Gas? (Marine Gas vs Premium Gas) - castineyachtclub.org (2023)

Marine gas usually has an octane level of 89 to 90 and is ethanol free, which is more than enough octane to power a boat. Using the right marine fuel in your boat’s engine, whether that be inboard, outboard, or sterndrive makes sure that your boat will perform well all season.

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If you have any queries regarding the oil and fuel requirements for your boat’s engine, the owner’s manual should be your first port of call. It’s important to make sure you adhere to the fuel and oil specifications in the manual.

What Octane Is Marine Gas? (Marine Gas vs Premium Gas) - castineyachtclub.org (1)

Not only to keep your boat running smoothly, but also so you’re in compliance with the warranty requirements.

But is marine gas better than premium gas? What is the difference between them, and what’s the best choice for your boat? We answer those questions below, as well as tell you all you need to know about ethanol and fuel stabilizers.

What Is Premium Gas?

The difference between premium gas and regular gas is that premium gas has a higher octane rating. Octane is a chemical component found in petroleum, and how much octane a fuel has will determine how effective it will be in higher compression engines.

Lower octane fuels are available, but can cause ‘knocking’ when added to your boat or car. ‘Knocking’ is when the combination of fuel and air in the engine’s cylinder head doesn’t burn correctly. This causes the engine to make a rough, pinging noise when it’s running.

At worst, lower octane fuel can damage your engine completely.

What Is Marine Gas?

It may surprise you that boats actually use the same gas as cars do! However, the big difference is how much you’ll pay for gas. The gas you’ll find at a gas station costs a lot less than the gas you’ll find at the marina because of supply and demand.

You can also use the same diesel you’d put in your car in your boat with a diesel engine too.

But bigger boats like ships will use different fuels depending on the engine design and type. These could be HFO (Heavy Fuel Oil), IFO (Intermediate Fuel Oil), MDO (Marine Diesel Oil), or MGO (Marine Gas Oil).

These fuels are the heaviest commercial fuels you can obtain from crude oil, meaning they’re heavier than gasoline and naphtha.

You can save a couple of cents if you fill up your small boat at a gas station instead of the marina, especially if you use a trailer to take your small boat to the marina.

What Kind Of Gas Should You Use In Your Boat?

Personal boats: As we have mentioned above, smaller, personal boats use the same gasoline as your car. You can use 87 octane unleaded gas, 89 octane mid-grade gas, or 93 octane premium gas or diesel.

The most important thing to remember though is that the gasoline shouldn’t have any ethanol in it (we’ll discuss that more below).

Larger boats: Larger boats have more specific fuel types and have a totally different classification to smaller, personal boats, which we have mentioned above. Marine Gas Oil (MGO) is a combination of light cycle gas oil and aromatics, and sometimes contains waste products such as used motor oil.

Meanwhile, Marine Diesel Oil (MDO) is a type of diesel that is made of heavy fuel oil. This is a totally different type of diesel to the type you would use to power your car.

Is Ethanol Safe To Use To Fuel Your Boat?

What Octane Is Marine Gas? (Marine Gas vs Premium Gas) - castineyachtclub.org (2)

There is some confusion about ethanol and whether it is safe to power your boat with it. Ethanol is tempting because it’s often cheaper than other types of fuel, but it’s recommended to not use ethanol if you can.

Ethanol can lead to a wide range of issues with your boat’s engine such as carbon deposits, moisture, and phase separation.

However, if you have to use ethanol-based gasoline, try to go for E10. If you’re unsure, you can take a look at the pump in the marina to confirm that you’re filling up your boat with ethanol-free gasoline, especially because some states like Missouri are not legally required to label their gas as containing ethanol.

What Are Fuel Stabilizers?

Fuel additives (or stabilizers) don’t have the best reputation, and are often compared to snake oil. But what is a fuel stabilizer?

You may have seen gasoline that is very dark, or you may have opened a gas can and noticed a strange smell. You may have even seen gasoline that just looks like varnish. All of these are the result of a chemical reaction that destabilized the fuel. Heat, light, and oxygen can all negatively affect your fuel.

Still, fuel stabilizer can’t fix gasoline once the chemical reaction has happened. But what it can do is prevent it from being destabilized in the first place, especially when it’s left to float for an extended period of time.

What Are The Advantages Of Using Gas To Fuel Your Boat?

  • Gas is often less expensive than diesel.
  • Gas produces less smoke than other fuels such as diesel.
  • Combining ethanol like E10 with gasoline decreases smoke pollution.

What Are The Disadvantages Of Using Gas To Fuel Your Boat?

  • Keeping ethanol gas in the tank for an extended period of time can corrode the fuel lines and even the tank itself.
  • It can be dangerous, as exhaust gases from gas engines contain carbon monoxide.
  • E15 ethanol combined with gasoline causes more pollution.
  • Gasoline motors do not produce the torque needed to run a bigger boat.

What Are The Advantages Of Using Fuel Oil In Big Ships?

  • Fuel oil is sometimes cheaper than gasoline.
  • Fuel oil produces 6.3 MMBTU/Gallon energy per gallon, while gasoline only produces 5.25 MMBTU/Gallon per gallon.
  • As gasoline can be a fire hazard, fuel oil is safer to store than gasoline.
  • Big ship engines turn at a significantly lower RPM and are not built to run on gasoline.
  • Fuel oil is thick and heavy, which not only powers the ship better, but it’s also more compact and leaves more room for cargo.

What Are The Disadvantages Of Using Fuel Oil In Big Ships?

  • Big ship engines are more expensive to get repaired, and fuel oil is more expensive to replace.
  • The thickness of the fuel makes it messier.
  • While fuel oil is less of a fire hazard than regular gasoline it does have its dangers. Bunker fuel is a low quality fuel that can cause particular harm to humans, such as serious illness or even death.

Final Thoughts

To sum up, boats, and smaller boats in particular, are powered by the same gasoline as cars, but it costs you a lot more to refuel at a marina than it would at a gas station. This is due to the supply and demand at the marina, which causes the marina to increase its prices.

While you can also use the same diesel to power your diesel engine boat as you would your car, gasoline is better for a smaller boat as it’s powerful while producing fewer emissions than other types of fuel.

However, this is not the case for bigger boats and ships, as they use different fuels and their own specific kinds of gas and diesel such as IFO, HFO, MGO, and MDO. These are heavier commercial fuels when compared to gas, and are obtained from crude oil.

Ships use fuel oils such as HFO and IFO because it is safer to use this type of fuel than the gas you’d use to fill up your car or smaller boats. All marine fuels, except for LNG, are legally required to have a flash point greater than 60C.

Petrol vapor is thicker than air, and any leaks would form in the lower parts of the ship. One spark could cause the engine room and the boat to explode.

But fueling your boat isn’t just about selecting the cheapest fuel and hoping for the best, you have to consider what the optimal fuel for your engine would be and what your engine requires.

You should always check your owner’s manual for the exact oil specification, but most manufacturers will require you to power boats with a four-stroke engine with oil that meets the FC-W certification.

You can check whether oil has this certification by looking for an FC-W symbol on the label. Oil that is FC-W certified protects from rust, which engine oils for cars cannot. It also imposes an increased minimum viscosity level.

This means that FC-W oil will not thin out like automotive oil with a similar viscosity when exposed to the same temperatures and RPM conditions. Meanwhile, Two-stroke outboards require oil that meets the TC-W standard.

So while you can use the same gasoline you would use to fuel your car to also fuel your boat, you should always consult with your owner’s manual in order to make sure you’re using a fuel that won’t damage your boat over time.

Premium oil isn’t better than marine gas either, as it simply just has a higher octane level.

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Lucas Jones

Hi, my name is Lucas Jones, and I have owned many boats over the years. Boating has always been a passion of mine, and I love nothing more than being out on the ocean, taking in the beauty and listening to the sound of the waves.

When I purchased my first boat, I didn’t realize how many things I needed to take into consideration, and I wanted a site like Castine Yacht Club, to assist me with all of the questions I had. Castine Yacht Club is the ultimate guide to everything related to boats, from reviews to informational topics.

Latest posts by Lucas Jones (see all)

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What is the octane rating of marine gasoline? ›

Although REC-90 is marketed to the marine industry and is commonly found at marinas, there are other octane levels of ethanol-free gasoline on the market such as ethanol-free 87 or 92 octane. While always refer to your owner's manual, these other common octane levels are typically suitable for marine engines.

What's the difference between marine gas and premium gas? ›

Marine fuel comes in basically the same octanes as automobile fuel. Higher compression engines take higher octane fuels to eliminate pre detonation in the cylinder. This happens in auto engines as well that are turbo aspirated, at sea level, and high compression ratios.

What is the octane rating for premium gas? ›

Regular (the lowest octane fuel–generally 87) Midgrade (the middle range octane fuel–generally 89–90) Premium (the highest octane fuel–generally 91–94)

What grade gas should I use in my boat? ›

What Type of Gas Should I Use in My Boat? All current outboard, sterndrive and inboard gasoline engines are designed to operate safely on fuel with no more than 10 percent ethanol (known as E10), and under no circumstance should fuel with more than 10 percent ethanol (such as E15 or E85) be used in a marine engine.

Can you put marine fuel in a car? ›

Marine fuels are very similar to the types of fuel you would use in your car, but they're created specifically for use in boats and other water craft.

Is premium gas 91 or 93 octane? ›

Premium gas is also often referred to as high-octane gas, thanks to an octane rating of 91 to 94. Regular gas typically has an 87-octane rating, and the 88-90 range is considered midgrade. While premium gas drives performance in certain engines, the idea that it's more fuel efficient is a myth.

Is premium gas better for outboard motors? ›

Current recommendations are to use a minimum of 87 octane, 89 octane is preferred. There is no additional benefit from using higher-octane fuels, in fact they may cause hard starting conditions in hot weather.

What gas should I use for my Mercury outboard? ›

Answer: Fuels containing up to 10 percent ethanol are considered acceptable for use in Mercury engines. Fuels containing higher levels of ethanol, such as E15 gasoline, are not considered acceptable for use. The use of fuels containing more than 10 percent ethanol can void the warranty.

Can I put 93 in my boat? ›

It burns as completely as a mid-range-octane or low-octane gasoline. In fact, 93 octane will perform just as well as lower octane; it just isn't necessary to spend the money on it. The only thing that gets damaged when you run 93 octane in a motor rated for lower octane is your wallet.

Who has the highest octane premium gas? ›

What is Sunoco Ultra 94? Ultra 94 is the highest octane fuel available at the pump at Sunoco. With 94 octane, it delivers the highest octane rating of any retail fuel on the mass market in the U.S., combined with Top Tier detergency to help make your engine run cleaner, longer, and more efficiently.

Is 93 octane the same as premium? ›

Premium gasoline is generally considered any type of gasoline with an octane level of 91 or greater, with 91 octane and 93 octane being the most common versions of premium gasoline available at gas stations in the United States (93 octane gasoline may be called “ultra” or “super-premium” in some cases).

What happens if I put 87 instead of 91? ›

If you put lower-octane fuel into your high-octane vehicle, whether by mistake or to save money on gas, you'll probably notice the effects right away: things like poor fuel economy, reduced acceleration, and spark knock, which sounds like a high-pitched pinging or rattling noise.

What is the name of marine gas? ›

MGO – Marine Gas Oil. MDO – Marine Diesel Oil. IFO – Intermediate Fuel Oil. MFO – Marine Fuel Oil.

What is the difference between marine grade fuel line and regular fuel line? ›

Marine-grade fuel hose is much heavier than the same inside-diameter hose as used in automotive applications. This is done as part of its fire or flame testing, a requirement under the regulations. All fuel hose used in engine room spaces on board gasoline-fueled boats must meet a 2.5-minute fire test rating.

What is the most used marine fuel? ›

HFO or heavy fuel oil is the most widely used type of fuels for commercial vessels. The fuel oil releases energy to rotate the ship propeller or the alternator by burning fuel inside the combustion chamber of the engine or to generate steam inside the boiler.

What to do if you accidentally put marine gas in your car? ›

If you put the wrong fuel in your car, get it towed to a mechanic where they will drain it out and make sure it's running smoothly.

Should I store my boat with fuel in it? ›

Marine engine manufacturers and technicians advise storing any boat with the fuel tank almost full, leaving just a little capacity to accommodate expansion of the fuel if the temperature warms.

What happens if I put 93 instead of 91? ›

“Use premium unleaded gasoline with a posted octane rating of 91 or higher. If the octane rating is less than 91, you could damage the engine and may void your vehicle warranty. If heavy knocking is heard when using gasoline rated at 91 octane or higher, the engine needs service.”

Is there really a difference between 89 and 91 octane gas? ›

Raising the octane rating (also known as the anti-knock index) doesn't change the energy content of a gallon of gasoline. A higher octane rating indicates greater resistance to knock, the early combustion of the fuel-air mixture that causes cylinder pressure to spike.

Which is better 93 or 95 octane? ›

The more stable higher octane fuel reduces the risk of igniting, allowing better performance and efficiency. The simple answer is that high performance cars require the higher 95 octane, while your average road vehicle will run suitably well on 93 octane.

What is the best gas for outboard motors? ›

Our top pick for boats with outboard motors is ethanol-free gasoline. If you go on your boat often and have enough money to invest in it, you should really consider avoiding ethanol. If you don't, there are two low-ethanol options that you can choose between: E10 fuel.

What octane gas for Mercury 2 stroke outboard? ›

Burning 87-octane gasoline in a two-stroke outboard causes carbon buildup that shortens engine life. Dose the fuel with a carbon-cleaning additive or fill the tank with 89-octane or higher fuel.

What is the best fuel mix for outboard? ›

25:1 - Mix 200ml of oil per 5ltrs of fuel.

This mixture is very rich and is usually recommended for running in brand new two stroke outboards and when running in rebuilt or reconditioned engines.

Is ethanol free gas better for boats? ›

Additionally, ethanol will slowly dissolve resins in older fiberglass tanks often used in boat motors. By choosing non-ethanol gas, you can prevent these issues and keep your boat's motor running smoothly.

Should I run the gas out of my outboard motor? ›

There is no harm in running your motor out of fuel with four strokes engines, but it's not necessary to do in most cases (again, refer to your owners manual).

Can you mix octane 91 and 93? ›

Yes, drivers can mix the two types of fuel. The combined gas types will result in an octane level somewhere in the middle — something the vehicle “will survive,” according to The Drive.

What happens if you put 93 instead of 95? ›


However, if you keep on running your car on 93 octane petrol instead of the required 95 octane petrol, your engine could start to knock. This, in turn, could cause serious engine damage.

What happens if you put 93 in your tank? ›

If you usually fill your tank up with 87-octane gasoline and you accidentally put in a higher octane blend (say, 91, 92, or 93), don't worry. You're actually filling your car or truck with a different blend of gas, which means it will burn differently in your engine.

Is there a downside to using premium gas? ›

A vehicle that does not need premium gas would still be benefited by the use of premium gasoline but, with the price, premium gas really isn't ideal. This makes premium gas a bit less valuable than standard as standard can be used in any car with only wear and tear being an issue after time.

Is Costco premium gas 91 octane? ›

Gasoline ​octane can vary by state, but at Costco, it's typically 87 octane for Regular and 91 octane for Premium Gasoline.

What octane is jet fuel? ›

The most common and reliable type of avgas is 100 octane Low Lead, also known as 100LL. This leaded fuel contains tetra-ethyl-lead (TEL), which is an additive used to prevent engine damage at higher power settings.

Is there a big difference between 92 and 93 octane? ›

Regular gas is rated at 87 octane in most states, while premium gas is often rated higher at 91 or 93. Fuel with a higher octane rating can stand up to higher compression before it detonates. Essentially, the higher the octane rating, the lower the likelihood that detonation happens at the wrong time.

What are the disadvantages of high octane fuel? ›

Simply put, higher octane gas won't lead to better car performance, more speed, better mileage, or your car running cleaner. Most cars require regular gasoline, and using higher octane means wasting your coins.

What happens if you use 89 octane instead of 93? ›

If you use a lower-than-recommended octane, fuel can combust too quickly for your engine to take full advantage of it. This combustion causes knocking, which sounds like a light pinging or rattling noise. It's a result of the air-fuel mixture in the cylinders igniting too early.

Is it worth putting 91 instead of 87? ›

The main difference with premium is its octane rating — 91 or higher compared with 87 for regular octane. The higher octane gives premium gas greater resistance to early fuel ignition, which can result in potential damage, sometimes accompanied by audible engine knocking or pinging.

What happens if you put 87 instead of premium? ›

However, remember this: when a premium fuel engine runs on regular fuel, there's a risk of combustion of the fuel mix before the spark plug even lights up. This causes a phenomenon called knocking, which is likely to damage the engine.

What happens if you accidentally put regular gas instead of premium one time? ›

Putting Regular Fuel in a Car That Requires Premium

Using lower octane fuel in a vehicle that requires premium gas could cause some serious internal damage. You'll most likely notice the spark knock (a sort of high-pitched pinging or rattling noise).

What gas is used in USMC gas chamber? ›

The gas chamber is a room that has a controlled concentration of CS (orto-chlorobenzylidene-malononitrile) gas, more commonly known as tear gas.

What color is marine gas? ›

MGO has a transparent to light color. If the marine fuel is used in inland waterway shipping, like heating oil it must be marked with Solvent Yellow 124 dye. In addition, the marine gasoil is colorized red.

What gas does the US Army use? ›

Under this policy, which has since been further standardized with our NATO allies, the United States military predominantly uses JP-8 fuel to run its ground vehicles and land-based aircraft.

What's the difference between marine gas and regular gas? ›

Marine fuel comes in basically the same octanes as automobile fuel. Higher compression engines take higher octane fuels to eliminate pre detonation in the cylinder. This happens in auto engines as well that are turbo aspirated, at sea level, and high compression ratios.

What's the difference between A1 and B1 marine fuel line? ›

If more than five ounces leaks, use “USCG Type A1.” If less than five ounces leaks, you may use “USCG Type B1.” “USCG Type A” hose may be used for all hose portions, regardless of whether the installation proves that “USCG Type B” hose is acceptable.

How often should marine fuel lines be replaced? ›

The EPA defines useful life as 10 years for boat fuel system components and five years for PWC fuel systems.

What happens if you put too much oil in a 2 stroke outboard? ›

What happens if the mixing ratios in a 2 stroke engine are incorrect? If you put too much oil, it can generate additional carbon build-up, making it difficult to start the engine, blow excessive smoke which is particularly bad for the environment and may (with time) cause the engine to stop operating correctly.

Can you mix marine gas with regular gas? ›

Yes you can mix the two. It is clearly better to run Ethanol Free gas in most outboards but if you have E85 or similar in your tank no worries about putting in Ethanol Free.

What happens if you run a 2 stroke engine without oil? ›

Running a 2-cycle with the wrong fuel to oil mixture can cause severe damage to your engine. Running the machine without any oil mixed in the fuel can cause severe damage to your equipment within just minutes. This damage is generally very costly to repair and is usually irreparable.

Can I run 87 octane in my boat? ›

All of the later model boats have high compression engines that were designed to run on 93 octane (US Octane) fuel. They all have the ability to run on 87 but that does NOT mean you are getting the best out of your boat.

What octane is Shell V-power gas? ›

With an octane rating of 99 RON, Shell V-Power is designed to provide more power and improved responsiveness in many modern cars.

Is Shell 91 octane? ›

vpower - 91 octane

Shell V-Power® NiTRO+ Premium Gasoline sets a new standard in fuels innovation and redefines protection. With a special formulation, Shell V-Power NiTRO+ Premium Gasoline delivers triple-action protection against gunk, wear, and corrosion for optimum engine performance.

What happens if you put 87 octane in 91? ›

If you put lower-octane fuel into your high-octane vehicle, whether by mistake or to save money on gas, you'll probably notice the effects right away: things like poor fuel economy, reduced acceleration, and spark knock, which sounds like a high-pitched pinging or rattling noise.

What happens if you use 89 octane instead of 91? ›

If the octane rating is less than 91, you could damage the engine and may void your vehicle warranty. If heavy knocking is heard when using gasoline rated at 91 octane or higher, the engine needs service.”

What happens if you mix 87 octane and 91 octane? ›

Yes, drivers can mix the two types of fuel. The combined gas types will result in an octane level somewhere in the middle — something the vehicle “will survive,” according to The Drive.

Is Shell V-Power 98 octane? ›

Shell V-Power is a 98 octane premium fuel which is designed to improve performance and act instantly in your engine. Developed as part of our long-standing technical partnership with Scuderia Ferrari, it contains 99% of the same compounds as the fuel used by the Ferrari Formula One team.

Is Shell V-Power 97 octane? ›

New Shell V-Power unleaded is a 99RON octane fuel. By comparison, regular Shell unleaded is 95RON.

Is Shell V-Power NiTRO the same as premium gas? ›

Now engineered with four levels of defense against gunk, wear, corrosion and friction to help keep your engine running like new*, Shell V-Power® NiTRO+ is America's best-selling premium gasoline brand and can be found across the country at approximately 13,000 Shell-branded stations.

What octane is kerosene? ›

Generally, the octane number (ON) of gasoline is in the range of 70–97, whereas the octane number of kerosene is much lower as only 20–50.

What is the best fuel for jets? ›

Jet A1 is the most used jet fuel worldwide. Jet A1 has a lower freezing point (-47° C) than Jet A (-40° C) so it is especially suitable for international travel through varying climates. This type of fuel also contains static dissipater additives that decrease static charges that form during movement.

What is the best fuel for jet engine? ›

Jet fuel or Kerosene

Jet fuel is a refined kerosene-based fuel widely functional in aeroplanes with turbine engines, turboprops and jet engines.

What is Shell premium gas called? ›

Shell V-Power® NiTRO+ Premium Gasoline.

Is Shell 91 ethanol free in USA? ›

The first is that you can simply avoid it in the first place. According to Dan McTeague, a noted petroleum analyst, Shell and Esso 91 are both ethanol free.

What's so good about Shell V-Power? ›

Shell V-Power is designed to slow burn and prevent premature ignition. Allowing timely ignition during combustion reduces harmful and power robbing cylinder knock.


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