The 4 Best Oils for Generators – Reviews 2024

best oil for generator

Photo by Institute for M, T, and FI / CC BY

There are few tools you will buy in your life that will be more handy than a portable gas generator. They are a savior when the occasional severe weather knocks out power and they can also turn any camping trip into a much more pleasant experience. Like any mechanical device they need routine maintenance and also to be kept in good running order.

A big part of that is maintaining the generator engine oil level and replacing it when necessary. Not all generator oils are created equal and we have taken the time to review some of the best ones in this article. Here is what we feel are the 4 best oils for generators.

Briggs & Stratton 30W Engine Oil – 48 Oz. 100028

There may be no better company to buy generator oil from than Briggs & Stratton. It is a name that is practically synonymous with quality small engines. Anytime you buy a product it is a huge advantage, if it is bought from a company with a reputable and trusted name. We were not surprised at the many highly favorable reviews of this oil at all.

Why choose this oil? For one it is specially formulated to work well and not break down easily on air cooled motors like portable generators have. This is very important when you have high engine operating temperatures, which is often the case with generators. It is also considered to be detergent type generator oil so it will help keep harmful residue from building up inside your generator engine.

This is a really convenient package size too. It is easily enough oil to do a complete oil change on most generators and still have enough left over to maintain your oil fill level where it needs to be. Hands down, it’s one of the best oils for generators.

Honda 08207-10W30 Motor Oil

Honda, in a very similar fashion to Briggs & Stratton, is another well-known company when it comes to manufacturers of quality small engines. It is pretty much guaranteed if they put their name on a product it will not only do the job but do it well.

This oil’s ideal viscosity means it well distribute itself throughout the engine quickly to lubricate all the parts and help keep the engine from running dry to long. Lesser-quality oils will take longer to lubricate your generators engine, which could lead to trouble. People who have used this oil faithfully for years have reported very few breakdowns with their equipment too. This oil is so well-made to this manufacturer’s specifications that they even consider it to be an OEM part.

Cummins 3265336 Onan SAE 15W-40 Oil – 1 Quart

This oil could be a little pricey but sometimes you get what you pay for and that is definitely the case with this specialty oil from Cummins. This company has long been making fine engines of all sizes so they really know engines well and will only sell you a product that keeps generator engines and other small engines running superb.

This is engine oil that is specially manufactured to provide maximum protection and it’s guaranteed to reduce engine wear and lower oil consumption. It is such a good product it is also considered an OEM part.

This oil will do a great job at lowering friction in your generators engine to ensure it has a long working life. All Cummins oils are extensively factory tested to make sure they maintain quality engine performance when using them. This should be on anyone’s list of the best oils for generators.

Briggs & Stratton SAE 5W-30 Synthetic Small Engine Motor Oil

We have already mentioned how Briggs & Stratton is a very reputable name when it comes to manufacturing and maintaining small engines. This is the only true synthetic oil on the list, and it’s a good one.

Synthetic oils are known to lubricate engines working parts faster than conventional motor oils. They also make excellent cold weather oils if you are going to be using your generator during the colder winter months. Not to mention that synthetic oils will eliminate a whole lot of wear causing friction in your generator engine when it starts to run hot.

The 32 ounce size should be more than enough for a generator oil change and still leave you with a little extra for that occasional top off. It really is magnificent oil when it comes to lubricating any 4 cycle/air cooled small engine like your generator has.

Engine Longevity Tip

It is highly recommended that you change your engine oil at least once a year in any product you have around your house that has a small engine (chain saw, lawn mower, etc.). The best time to change it is just before each particular gas-powered item’s season of main use (example: early spring for a lawn mower).

You should also change the oil any time you notice that it has become contaminated with such things as water or debris. Always make sure the oil level in each gas powered item you own is always at the recommended fill level too.

Helpful Tip

If you are buying these products because you are going to do an oil change on your generator then why not make it more of a tune up than just an oil change. This can be done very cheaply and all you will need to do is replace the oil, the gas filter, and the spark plug on your generator. It will go a long way toward keeping the working parts of your generator running smoothly for years to come.

Don’t get fooled into thinking all oils are the same. There is a reason why these have our recommendations for the best oils for generators. They’re all made to lofty standards and that is because they really know what products are healthy for small engines. When buying oil for your generator you can’t go wrong using any of the oils that were reviewed here. Good luck!

  • Founder of Mechanical Caveman, Beau is an unrepentant tool enthusiast and, sporting deadlift-callused hands and an incongruous beer belly, all-around macho guy. When he doesn’t know re tools, he consults with his handyman and car-repairman buds to give you well-reasoned and cutting-edge info.

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4 responses

  1. the infomation above is very helpful for keep my briggs and stratton generator in shape for emergency like the one just pass thru puerto rico.thanks a lot.

  2. I think you’re buying into advertising hype. B&S, Honda, & Cummins all make fine oil. So do dozens of other companies (…well, maybe five or six, which get rebranded to dozens of other name).

    Test after test, the results show that there is little difference between regular oils, and not much between full synthetics, either. What is important is NOT the brand of oil. There are three things that really DO make a difference: (1) Change your oil at least as frequently as recommended by the manufacturer, if not MORE often, especially on engines that aren’t used for an extended period, like yard machines and many generators. (2) Buy oil that, at a minimum, meets the API Service code(s) and viscosity grade (say, 5W-30) ordained by the manufacturer. If you’re still under warranty, make certain you use oil that EXACTLY meets the API code and viscosity grade mandated in the owner’s manual (anything else may void your warranty). Many (most?) generator manufacturers, if you ask them, will tell you to use regular oil for the break-in period (first 50 hours or so) because the less-good lubrication helps all the parts seat themselves, and then if you want, you can use synthetic oil…it really does last longer and protect your engines better. So if you’re beyond the warranty period and want to get the benefits of using synthetic oil, go for it…but get a synthetic of the right viscosity, with API Service SN. (3) Perform other routine maintenance on a regular basis – at the least, get a HIGH QUALITY air filter and properly gapped spark plug every year.

    • I worked for an oil company few years ago and we repackaged our oil for Castro, Mobil and shell. I am sure there are a few others I have forgotten but it’s well known in the industry to package products and slap another makers name on it.

  3. Just installed an Onan 4000 micro quite generator. Have about 30 hrs. on it. Ran it quite long with those 30 hrs.
    Was going to go synthetic but it seems like I should go conventional for the next go around then go synthetic.
    Changed the air filter.
    Thank you.

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