Sierra eGuard is the first fuel additive from the Teleflex brand that specializes in oils and engine components, and as the name implies, it’s a formulation the company says is specifically designed to be compatible with – and defend against – ethanol-blend fuels. You can use it with ethanol blends up to E85, although I’m not aware of any marine engine that can tolerate that much ethanol. It’s claimed to address the problem of phase separation, which occurs when water attracted to ethanol in the fuel reaches a saturation point, causing most of the water and ethanol to drop to the bottom of the fuel tank. Sierra eGuard is said to disperse water throughout fuel in small particles that can pass through the engine. This stuff is also a fuel stabilizer and acts to remove carbon and gum deposits from the fuel system and combustion chamber.


The 32-ounce bottle of Sierra eGuard has an built-in measuring reservoir.

For most boat owners, the fuel stabilizing action of eGuard will probably its most-important feature. I have talked to a number of marine-engine techs who say that problems related to “stale” fuel are now the number-one issue in their shops. Modern gasoline, whether it’s blended with ethanol or not, can begin to oxidize and form deposits in the fuel system in a matter of weeks. We used to only use fuel stabilizer for winter storage, but unless you are burning through a tank of gas promptly fuel stabilizer should be added with every fill-up. And if you have to buy ethanol-blend fuel, using a product like Sierra eGuard that attempts to address ethanol-related issues makes sense.

I’m no chemist, and I live in the enlightened state of Wisconsin, which does not require me to buy ethanol-blend fuel, so I can’t verify any of the claims Teleflex is making for Sierra eGuard. But I can rave about the 32-ounce bottle it comes in. It incorporates one of the handiest built-in measuring chambers I’ve seen on a fuel additive bottle. This is important, because you only need to add one ounce of eGuard to 10 gallons of fuel. And eGuard is not cheap, so you don’t want to waste it. Open the cap, squeeze the bottle, and product is transferred to the reservoir. Other bottles have a measuring reservoir, but what I like about this one is that it’s angled to make it easy to pour into a portable or built-in tank. It’s also shaped so that it’s possible to pour some back into the main bottle if you over-fill the reservoir.

Sierra eGuard is available in the 32-ounce bottle ($24.99) and in an eight-ounce bottle ($8.99) which does not have the measuring reservoir. It can be used in any two-stroke or four-stroke gasoline marine engine. Teleflex has sent me a 32-ounce bottle of Sierra eGuard, which I’ll be trying in a variety of gasoline-powered devices this summer. In the meantime, add a comment if you have any experience with this new product.