To Add an Additive or Not

Should they be used with Harley Davidsons?

Which oil additive is best for my air cooled Harley?

Via Email

Using an oil additive is actually “old school thinking”. Many years ago the oil that was available to us did not offer much protection for our Harley Davidson motorcycles. In 1941 ZDDP (Zinc dialkyldithiophosphate) was developed and manufacturers began to put it in their oils. Even today, ZDDP is the most commonly used anti-wear additive in motor oils. It contains both Zinc and phosphorus components that work together to provide anti-wear protection and minimize lubricant breakdown. ZDDP also has mild extreme-pressure protection. Zinc, viscometrics, and base stocks are the oil contents that control the wear of moving metal parts. However, while Zinc is important in protecting against wear, the biggest concern should be in using a well balanced oil that is designed for its intended application. ZDDP works by decomposing when temperatures rise and surfaces come closer together. The resulting chemistry is what protects the critical, working metal surfaces.

So why not use an oil additive?

Won’t adding more ZDDP give even better protection to your 20/50?

Well, the old saying, “too much of a good thing can be a bad thing” rings true here. Whether you are running Screamin’ Eagle, Bel Ray, Spectro oil….. these oils are all balanced and already have the correct amount of ZDDP for their intended application which is your Harley Davidson. If more ZDDP is added, it will just burn past the rings and collect in the exhaust ports and in the exhaust system. If your Harley has a catilidic converter, it will become coated and eventually blocked from the excess ZDDP burn off, restricting the motor from breathing correctly.

There are automotive and diesel applications where oil additives are beneficial. However, when it comes to your Harley Davidson, a quality synthetic oil is best.

In regard to Fuel Additives:

GASOLINE & ETHANOL

Ethyl alcohol, or ethanol is a grain alcohol fuel additive usually made from corn. In America, Ethanol is blended into our gasoline for two main reasons: To reduce our dependency on foreign oil and to help reduce tailpipe emissions.

In gasoline, Ethanol is used as a biofuel filler. Ethanol is an octane booster and an oxygenate. Pure ethanol has an octane rating of 130. Oxygenates are compounds that contain oxygen in their chemical structures and contribute to the combustion process. Oxygenates help to eliminate unburned hydrocarbons by helping them burn.

Most gasoline in the states contains up to 10 percent ethanol and is called E10. E10 is known to cause problems for fuel systems on older motorcycles especially during long term storage. Ethanol is corrosive. It can cause hoses and gaskets to swell or deteriorate. Pre-2000 bikes are much more ceceptable to these issues. Ethanol resistant fuel system components are used in almost all bikes & automobiles manufacturered after 2000.

Even if your motorcycle was made after the year 2000, you can still have issues with ethanol if you leave your motorcycle in storage for an extended period of time. Sometimes as short as thirty days or, more commonly, a (winter) season is enough for fuel to turn bad.

This is because ethanol is hydrophilic. Which means, it attracts and binds to water. Even to water vapor. If ethanol absorbs enough water, it separates and sinks to the bottom of the fuel tank. Ethanol is the primary octane in gasoline. So when the ethanol separates & sinks, the gasoline toward the top of the tank could end up with an octane rating in the lower 80s. For this reason, it is important that a fuel stabilizer is added when you plan to park your motorcycle for an extended period of time.

There are a number of good choices when it comes to fuel stabilizers for your Harley Davidson. There are a lot of well known companies that manufacture fuel stabilizers and additives. Some are considerably more expensive than others. Ask your buddies what they like, or what they have used. Find what fuel additive might work best for you to keep your fuel system clean.