Handyman’s Place is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

10 Best Oils for Generators of 2021 – Reviews & Top Picks

close up AmazonBasics AM0D533Q Full Synthetic Motor Oil

Whether you rely on your generator only occasionally to keep the lights on when the power’s out, or you use it every day in your RV setup, your generator’s needs are the same. It requires regular oil changes with a high-quality oil meant to reduce friction and keep your generator running. A failure here could mean no generator when it’s needed most.

We want to make sure that you’re never left in the dark due to wear and tear or picking the wrong product, so we decided to figure out exactly which oils could be trusted to power generators. To do so, we used many different brands of oil, comparing our findings in the following 10 reviews.


A Quick Comparison of Our Favorites

Image Product Details
Best Overall
Winner
Castrol 03129C EDGE High Mileage Motor Oil Castrol 03129C EDGE High Mileage Motor Oil
  • Extra fluid titanium technology
  • Increased fuel economy
  • 30% greater oil film strength
  • Best Value
    Second place
    AmazonBasics AM0D533Q Full Synthetic Motor Oil AmazonBasics AM0D533Q Full Synthetic Motor Oil
  • Fully synthetic
  • Resists thermal breakdown
  • Reduces exhaust emissions
  • Premium Choice
    Third place
    Generac 0J5140 Full Synthetic Motor Oil Generac 0J5140 Full Synthetic Motor Oil
  • Superior viscosity breakdown protection
  • Synthetic base with additional additives
  • Prevents sludge and varnish deposits
  • STP 18589 4 Cycle Oil Formula STP 18589 4 Cycle Oil Formula
  • Made specifically for small engines
  • Controls engine oil viscosity
  • Creates a protective layer at high temps
  • Cummins 3265336 Onan SAE 15W-40 Oil Cummins 3265336 Onan SAE 15W-40 Oil
  • Perfect for Onan generators
  • Pack of 4
  • Maximum protection formula
  • The 10 Best Oils for Generators – Reviews 2021

    1. Castrol 03129C EDGE High Mileage Motor Oil – Best Overall

    Castrol 03129C EDGE High Mileage Motor Oil

    Castrol EDGE high mileage motor oil is made to keep high mileage vehicles running longer, so it stands to reason that it would be a great choice to keep your generator running longer as well. But there are more benefits than just an improved lifespan. This oil features extra fluid titanium technology, which increases oil film strength up to 30% while reducing its breakdown.

    When using this oil, you can expect increased fuel economy. Since it’s a fully synthetic formula, you won’t have to change it as often as non-synthetic oils. And this formula is also made to be 10 times stronger against high-temperature oil thickening.

    Granted, this oil is not made specifically for small engines like some of the other options on this list, but that means it’s also much more affordable. And if it can be trusted with our vehicles, there’s no reason we can’t trust it in our generators as well.

    Pros
    • Extra fluid titanium technology
    • Increased fuel economy
    • 30% greater oil film strength
    • 10X stronger against high-temp oil thickening
    • Fully synthetic formula
    Cons
    • Not made specifically for small engines

    2. AmazonBasics AM0D533Q Full Synthetic Motor Oil – Best Value

    AmazonBasics AM0D533Q Full Synthetic Motor Oil

    Generators are already expensive, but maintaining one doesn’t have to be. The AmazonBasics full synthetic motor oil is a great option that saves you quite a bit of money over other oils you could use in your generator. This oil comes in many different weights, so you’re sure to find exactly the oil you need.

    Since it’s fully synthetic, this oil lasts longer and provides superior protection to your generator’s engine against wear. This particular formula is built to resist thermal breakdown while reducing exhaust emissions, making it particularly desirable for anyone concerned with their carbon footprint.

    We had just one problem with the AmazonBasics oil. Usually, there’s a clear stripe on the side of the bottle with graduated markings so you can see how much oil is left. This makes it easy to refill precisely the correct amount, but these bottles are missing that crucial piece. Still, the oil is great and is one of the best oils for generators for the money. But it’s recommended that you keep another oil bottle around for precise filling!

    Pros
    • Priced affordably
    • Fully synthetic
    • Resists thermal breakdown
    • Reduces exhaust emissions
    • Available in many weights
    Cons
    • Can’t tell how much oil is in the bottle

    3. Generac 0J5140 Full Synthetic Motor Oil – Premium Choice

    Generac 0J5140 Full Synthetic Motor Oil

    Generac is known for making a wide range of exceptional quality generators, so it stands to reason that they know a thing or two about what generators need when it comes to oil. They make generators of every size, from small portable generators to home and business backup generators, up to industrial power mega generators.

    This synthetic motor oil is the original equipment manufacturer (OEM) oil for use in Generac generators. It’s a synthetic base with additional special additives to ensure your generator runs problem-free for many years. Since this is the recommended oil in Generac manuals, it’s the best and safest choice for Generac generators in particular, though it’s also an excellent option for other generators.

    With this oil, you get superior viscosity breakdown protection, so your oil keeps working well over time, not just when you first change it. Furthermore, this oil prevents sludge and varnish deposits from accumulating inside your engine, ensuring long-lasting performance. Of course, you’ll be paying a premium for that performance as this is some of the most expensive oil we’ve seen. But if you can afford it, it’s like buying peace of mind.

    Pros
    • Superior viscosity breakdown protection
    • Prevents sludge and varnish deposits
    • Synthetic base with additional additives
    • Generac OEM for Generac generators
    Cons
    • Very expensive

    4. STP 18589 4 Cycle Oil Formula

    STP 18589 4 Cycle Oil Formula

    Your generator has a small engine, so why not use oil in it that’s specifically meant for a small engine? It only makes sense. Well, this STP 4-cycle oil formula is made just for small engines, and it’s got some features to help keep them running longer and better.

    This oil is made to control the viscosity, preventing it from getting thinner as it breaks down. It creates a protective layer at high temperatures that helps to reduce wear and tear, allowing your generator’s motor to last much longer.

    Like most specialty oils, this formula isn’t cheap. It’s far from the most expensive we’ve seen though. At least this blend offers some improvements for the price, like detergents to keep the inside of your engine clean and corrosion inhibitors to prevent problems while the generator is being stored.

    Pros
    • Made specifically for small engines
    • Controls engine oil viscosity
    • Creates a protective layer at high temps
    • Reduces engine wear
    Cons
    • It’s certainly not cheap

    5. Cummins 3265336 Onan SAE 15W-40 Oil

    Cummins 3265336 Onan SAE 15W-40 Oil

    The Onan line of Cummins generators are the best-selling RV generators ever. They’re known for their longevity, lasting many years without issue. If you have one of these iconic generators and you want to ensure that it lasts as long as you hope, then using the Onan OEM oil is a great choice since it’s specifically made for the Onan generators.

    This is the maximum protection formula, meant to keep your generator running with low friction and high dependability. It’s extremely expensive stuff, but if you own an Onan generator, you already know that they’re quite pricey on their own. We trust the Onan oil in our Onan generators, but if you have another type of generator, then you can certainly save money by choosing another reputable brand instead.

    Pros
    • Perfect for Onan generators
    • Pack of 4
    • Maximum protection formula
    Cons
    • Wildly expensive

    6. Briggs & Stratton 100074 SAE 5W-30 Motor Oil

    Briggs & Stratton 100074 SAE 5W-30 Motor Oil

    Briggs & Stratton are known for making quality small engines. Not generators specifically, though they do produce those as well. This 100074 SAE 5W-30 oil is made to work in small engines from a brand that could definitely be considered experts on the subject.

    Briggs & Stratton motors are known for lasting a long time, and this oil could be a part of the reason. It’s fully synthetic, so you can go longer between changes and it will provide better protection against heat and friction.

    But this is pretty expensive oil, even compared to other blends meant specifically for smaller engines. In truth, it doesn’t seem to offer improved performance. That doesn’t mean it doesn’t work well; it does. But is it something special that’s worth paying extra for? We don’t think so.

    Pros
    • Made specifically for small engines
    • Fully synthetic formula
    • Engines last a long time
    • From the small engine experts
    Cons
    • It’s pretty pricey
    • Doesn’t seem to offer improved performance

    7. Briggs & Stratton 100028 Engine Oil

    Briggs & Stratton 100028 Engine Oil

    As we’ve already mentioned, Briggs & Stratton are known for making high-quality small gas engines. With this background, we expect them to know about the fluids that need to fill these motors. This 100028 engine oil isn’t meant specifically for small engines, though other oils from Briggs & Stratton are. That said, this oil is still warranty certified and recommended in all their motors, but we prefer the small engine specific blend.

    What’s great about this formula is the affordable price. It’s for 4-cycle engines only, so you won’t want to use it in your 2-cycle motor. This oil comes in a larger 48-ounce container, so you won’t need as many bottles total.

    Pros
    • From a company based around small engines
    • Warranty certified in all Briggs & Stratton manuals
    • Affordably priced
    Cons
    • For 4-cycle engines only
    • Not made specifically for small engines

    8. ROYAL PURPLE 15W40 Synthetic Diesel Motor Oil

    ROYAL PURPLE 15W40 Synthetic Diesel Motor Oil

    Royal Purple is a controversial motor oil. This blend claims to offer some great features like improved compatibility with ethanol fuels. Moreover, this 15W40 synthetic blend is supposed to offer better fuel economy while protecting the emissions system. It also supposedly provides superior defense against corrosion.

    These claims might be true, but in our experience, we could find nothing special about this oil. Our generators ran just fine using this oil, but not any better than with other oils we tested.

    Also, it’s worth noting that Royal Purple has been in trouble recently for false advertising. Many claims they had made about their products had been proven false. They’ve likely learned their lesson, but it still leaves a lot of doubt regarding any claims on their oils, including this one.

    Pros
    • Protects the emission system
    • Improved compatibility with ethanol fuels
    • Better fuel economy
    • Synthetic formula
    Cons
    • It’s very expensive stuff
    • Seems to operate like regular oil
    • Royal Purple has been in trouble for false advertising

    9. Honda 08207-10W30 Motor Oil

    Honda 08207-10W30 Motor Oil

    Honda motors are often heralded as long-lasting motors with top-notch dependability. As such, they’re some of the most expensive generators on the market. If you own a Honda generator, they insist that you continue using Honda oil in your generator. It’s what’s suggested in the manual and since this oil is OEM for Honda, it’s a great choice.

    That said, if you own a generator other than a Honda, we’d recommend going with another brand. This oil doesn’t offer anything special for the expensive price you pay. You’re essentially paying for the Honda name. This 08207-10W30 blend isn’t even synthetic. For this price, you can get fully synthetic oil from other brands that will suit you just as well or even better.

    Pros
    • Perfect for Honda generators
    Cons
    • Overpriced because of the brand name
    • Not synthetic

    10. Delo 400 SAE 30 Motor Oil

    Delo 400 SAE 30 Motor Oil

    The Delo 400 SAE 30 motor oil is available in bulk volumes up to 5 gallons. That can save you quite a bit of money over purchasing it by the quart. But that’s our favorite thing about this oil. It’s not synthetic, though it’s priced high enough to make you think it is.

    You can’t use this oil in 2-stroke motors. It’s only compatible with 4-stroke motors. When you’re pouring it, you’ll have to guess how much you’re using since there’s no way to tell on the bottle. It’s a bit cheaper than some options, but since it’s not synthetic and also not made specifically for small motors, we’d recommend skipping it in favor of something that meets those criteria.

    Pros
    • Available in bulk
    Cons
    • No markings to see how much you’ve poured
    • Not recommended for use in 2-stroke motors
    • Not small motor specific

    divider 9

    Buyer’s Guide

    There are many different oils you could choose for your generator. But if you put the wrong oil in, you’re sure to end up with some serious issues. If you’re already experienced with small motors, then you might not need the following information. But if you’re unsure about what to fill your generator with on its next oil change, then this buyer’s guide is for you.

    Make Sure You Choose the Right Oil

    If you don’t know much about engines, then oil might seem almost trivial. You just grab oil and pour it in, right? Well, you could, but your engine likely wouldn’t function right. There are a few things that you’ll need to make sure of before adding oil to your engine.

    Check the Manual for the Proper Weight

    The most important thing to get right is putting the proper weight oil in your generator. Putting oil of the wrong weight in is one of the biggest mistakes you can make here.

    Luckily, it’s pretty easy to make sure you’re putting the right oil in. All you have to do is open up the user manual for your generator and find the section where it discusses maintenance. Here, it should list precisely what oil you need to add.

    Once you determine what weight oil your generator needs, you can pick just about any oil at that weight. Any of them will work, though there are still differences that can cause some to perform better than others.

    Synthetic vs Conventional Oil

    Synthetic oil offers quite a few advantages over conventional oil. To start, it resists breakdown for much longer, meaning you can go longer between oil changes. Going further, synthetic oils are able to withstand higher temperatures, which means they can keep your engine running better for longer.

    If you ever use your generator in cold weather, synthetic oil offers advantages here too. Synthetic oil can flow much better in cold temperatures. This means easier startups and considerably less engine wear when the oil is cold.

    Granted, synthetic oil is quite a bit more expensive than conventional oil. But with so many advantages, it’s a cost we’re always willing to pay.

    OEM is Always Safe

    If your generator is from a major name brand, you can’t go wrong by sticking with the OEM product that’s recommended for your generator. Generally, this will be an oil from the same company. While that oil might not provide superior benefits over other oils, you definitely can’t go wrong by picking what’s recommended for your specific generator.

    Also, some brands will only honor warranties if their specific oil is used. Other oils, even of the proper weight, will void the warranty. It’s also possible that certain brands use special additives to make sure their oils work well in specifically their generators since they know precisely what their machines need to run at peak performance.

    Ensure You Get the Right Amount

    Another important consideration is how much oil you need. Oil comes in quarts, gallons, five-quart containers, and even five gallons. Of course, you’re unlikely to need five gallons of oil to fill your generator. Still, you should know exactly how much oil you need so you can avoid overbuying, and more importantly, overfilling.

    Again, this is a simple thing to find out. Open up the manual for your generator and find the maintenance section. It should tell you exactly how much oil you’ll be replacing. Alternatively, this information is most likely available online as well.

    How Often Should You Change the Oil?

    It’s important to keep up with the upkeep of your generator if you want it to function its best for many years. As such, you’ll want to follow the manual’s guidelines regarding how often you should change the oil.

    As a rule of thumb, new generators usually need their first oil change after 25 hours of use. After this, you’ll want to perform regular oil changes after every 50 or 60 hours of use. But again, this is something you’ll need to confirm in the manual for your specific generator.

    divider 8

    Conclusion

    There are many different oils on the market with varying formulas and features. They span different weights and come from many manufacturers. As you’ve seen in our reviews, they’re all usable, but they’re not all equal. It could be catastrophic if your generator isn’t working when it’s needed, which is why we’re making recommendations that we’re confident won’t let you down.

    Castrol EDGE high mileage is our top pick. This fully synthetic formula offers increased fuel economy and extra protection against high-temperature oil thickening. You’ll get 30% greater oil film strength and reduced breakdown and friction.

    The AmazonBasics oil comes in many weights and is one of the most affordable oils we’ve seen, though it’s still fully synthetic and resists thermal breakdown while offering reduced emissions.

    And it might be expensive, but Generac full synthetic motor oil is our premium choice pick. It comes from a brand that specializes in generators of all sizes and this is their OEM oil that’s recommended in their generators. This oil has a synthetic base with special additives that can help keep your generator running longer with superior viscosity breakdown protection while preventing sludge and varnish deposits in the motor.

    Related posts

    Other categories

    Project ideas

    Hand & power tools

    woodworking

    Garden

    Automotive