One of the easiest things you can do for your outboard is run Top Tier gasoline. Not premium. Top Tier. They're not the same thing, and the difference matters more than most boat owners realize.
Top Tier is a fuel performance standard created in 2004 by a group of major engine manufacturers. GM, BMW, Honda, and Toyota were the original sponsors. The program has since grown to include Ford, Volkswagen, Mercedes-Benz, Audi, and others. These manufacturers got together because they weren't satisfied with the EPA's minimum detergent requirements for gasoline. They wanted more.
The EPA sets a baseline. Every gallon of gas sold in the U.S. must contain a minimum level of detergent additives. Top Tier requires significantly more than that minimum. Fuel brands that want the Top Tier certification have to meet stricter detergency standards, pass independent engine testing at an ISO-certified lab, and maintain those standards at every station that carries their brand.
As of 2026, there are over 100 licensed Top Tier retail brands across more than 100,000 stations in North America.
Your outboard's fuel injectors are precision components. They fire thousands of times per minute, delivering a carefully metered spray of fuel into the combustion chamber. When detergent levels in the fuel are low, carbon deposits build up on the injector tips, inside the combustion chamber, and on intake valves. Over time, those deposits restrict fuel flow, distort the spray pattern, and throw off the balance between cylinders.
That's when you start noticing it. Rough idle, sluggish hole shot, reduced top-end speed, increased fuel consumption. The engine still runs, but it's not running right. And every hour on low-quality fuel makes it a little worse.
We see this on the bench constantly. Injectors come in clogged with carbon and varnish that built up over seasons of running cheap gas. The before-and-after flow data tells the story. Some injectors are 10-15% below spec before cleaning. Top Tier fuel won't eliminate the need for injector service forever, but it significantly slows down the buildup that causes these problems.
This is the most common misconception we hear. A lot of boat owners think buying premium (93 octane) means they're getting better fuel. They're not. They're just getting fuel with a higher octane rating.
Octane measures how resistant the fuel is to pre-ignition (knocking) under compression. Higher-performance engines with higher compression ratios need higher octane to prevent knock. That's it. A higher octane number doesn't mean more detergent, better quality, or cleaner fuel. If your engine is rated for 87 octane, putting in 93 does nothing except cost you more money.
Top Tier, on the other hand, is about what's in the fuel besides the gasoline itself. Specifically, the detergent additive package. A station can sell 87 octane Top Tier gas that's better for your engine than 93 octane from a station that doesn't meet the Top Tier standard.
Bottom line: Check your engine manual for the recommended octane and use that. Then make sure wherever you buy it carries the Top Tier certification. That's the combination that actually matters.
Most major gas station brands are Top Tier certified. Shell, Chevron, ExxonMobil, Costco, QT, and many others carry it. However, a lot of convenience stores, independent stations, and smaller truck stops are not. The fuel might be fine, but without the Top Tier certification there's no guarantee of the detergent levels.
The easiest way to check is to look for the Top Tier sticker on the pump. If you don't see one, you can search by location at stationfinder.toptiergas.com or download the Top Tier Station Finder app on your phone.
One important note: the Top Tier standard applies to all octane grades at a certified station. So if the station has the certification, their regular 87 is Top Tier just like their 93.
If you're filling up at a marina or a dock that doesn't carry Top Tier fuel, a marine fuel additive with a detergent boost can help bridge the gap. Products like Chevron Techron Marine are specifically designed to supplement the detergent levels in non-Top Tier fuel. It's not a perfect substitute, but it's better than nothing, especially if you're running non-Top Tier fuel consistently.
Also worth noting: ethanol is a separate issue. E10 (10% ethanol) is standard at most stations and safe for modern outboards. The real problem with ethanol is when fuel sits in the tank for weeks without being run. That's when phase separation and moisture issues start. A fuel stabilizer addresses that. Top Tier addresses the detergent and deposit side of the equation.
Running Top Tier gasoline isn't going to transform your engine overnight. But over a season, over two seasons, the difference in carbon buildup is measurable. We clean a lot of injectors that could have stayed cleaner longer with better fuel. It's one of those maintenance habits that costs almost nothing extra and pays off over the life of the engine.
Clean fuel in, clean combustion out. That's the idea.
Already dealing with rough idle, poor fuel economy, or injectors that aren't performing? We can help. Ship your injectors to us for professional ASNU cleaning and flow testing, starting at $25 per injector.
Professional injector service that performs — You ship 'em and we take care of the rest. Done.
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