There are a lot of myths surrounding motorcycle fuel—especially when it comes to the octane rating of the fuel.
Higher octane numbers were always seen as better, but is that really the case? Many riders even to this day swear by higher octane fuel.
This is when some questions can pop up in the mind of some riders, namely about using 110 octane fuel in their Harleys.
Can I put 110 octane in my Harley? Harley-Davidson recommends that riders should use 92 octane fuel or higher. Most Harley motorcycles can use 110 octane fuel. However, if you put 110 octane in your Harley, it will not run faster, and you can damage it if the motorcycle is not properly tuned to run 110 octane fuel.
If you are interested in learning a little more, continue reading below. By the end of this article, you will know whether or not running 110 octane fuel in your Harley is worth doing. We will also clear up some common myths about what fuel is best for the Harleys.
So let’s take a look.
What kind of fuel do Harley-Davidson motorcycles use?
Before we continue, I should mention that you should always refer to the owner’s manual for this kind of information as all manufacturers will include information about what type of fuel each motorcycle should use.
There are three types of fuel you will find on most gas stations. Gas stations usually offer regular fuel (normally, 87 octane), plus fuel (between 88 to 90 octane), and premium (between 91 to 94 octane). However, some places can still offer race fuel, which is usually 110 octane or more.
So what kind of fuel do Harleys use?
Thanks to high compression ratios, current Harley-Davidson motorcycle engines use 91 octane or higher premium fuel.
Does using 110 octane in your Harley make a difference?
Let’s clear out a few common misconceptions:
- Higher octane fuel does is not more powerful.
- Higher octane fuel is not more thermally efficient.
- It doesn’t make the motorcycle faster.
- And it doesn’t make the engine run better.
So what exactly can 110 octane fuel do for your motorcycle, then?
By simply putting 110 octane fuel in your Harley, you will not see any positive difference. A higher octane number by itself cannot really add more horsepower.
To take advantage of fuel with a higher octane rating, you need to run either an engine that is manufactured specifically for running higher octane fuel or an engine that has been modified.
A 110 octane simply means the fuel will self-ignite later compared to an 87 or 91 octane fuel, for example. With a higher octane fuel, you can run more timing, which increases the engine’s high-end power. In this case, running a 110 octane fuel will make a difference, but running it on an unmodified engine will usually not make any tangible impact.
Motorcycle engines (and engines in general) generate different amounts of pressure as the piston goes up and compresses the fuel. When the fuel is compressed by the piston and the piston has reached its top dead centre (TDC), the spark plug generates a spark that ignites the fuel.
While the piston is at the Top Dead Centre (TDC), the fuel will be subjected to a lot of pressure. If the fuel is of the wrong octane rating, it may self-combust before the spark plug fires.
A higher octane rating fuel can withstand more pressure than a lower octane fuel. This means that if your engine generates a lot of pressure (meaning it takes high octane fuel) and you feed it with low octane fuel, the fuel will self-combust prematurely—this is also known as pre-ignition.
You want the spark plug to ignite the fuel—and not the fuel to self-ignite on its own. If the fuel pre-ignites, this can cause engine knocking, which will wear out and damage the engine’s internal parts.
Can 110 octane fuel hurt a Harley?
Using fuel with an octane rating that is not suitable for a Harley’s engine may hurt the motorcycle in the long run. However, if the engine has been properly tuned for a 110 octane fuel, it will not damage it.
There used to be some misunderstanding a while ago that some Harleys had a knock sensor and thus could adjust the timing and fine-tune the fuel management if lower octane fuel was used, for example.
Small differences in octane are usually not a big problem. However, you can run into some issues if you are running high octane fuel in an engine that has been tuned for low octane fuel—in other words, running a 110 octane fuel in an engine tuned for 87 octane.
For example, some of the older EVO engines run best on 87 octane fuel, while higher octane fuel (89 to 94) usually makes them run worse.
And vice versa—running an engine modified for high octane fuel with very low octane fuel.
In this case, running fuel with not enough octane usually results in pre-ignition, leading to engine knocking and increased cylinder temperatures. In fact, running low octane fuel may be more damaging to the engine than using high octane fuel.
In addition to all that, higher octane fuel can also be leaded, which poses another set of issues. Leaded fuel can damage the o2 sensors and the catalytic converters, foul the plugs, accumulate lead deposits in your crankcase, and even wear down the coating on the valves. This is why riders often will mix it with unleaded fuel in order to mitigate the risks.
Sometimes 110 octane fuel can high amounts of ethanol. Ethanol can be very detrimental to motorcycle engines. Usually, the majority of motorcycles built today can handle up to 10% ethanol. And the fuel gas stations sell usually has about 10% ethanol in it.
However, going above that is not recommended by the majority of manufacturers. Some may even void the motorcycle’s warranty if fuel with high ethanol content has been used.
Can you run 110 octane in a Harley?
You can run 110 octane in a Harley. However, running a 110 octane fuel in your Harley will not result in higher output and more power. In fact, while running 110 octane in a Harley may not necessarily be bad for the motorcycle, you could experience a drop in the motorcycle’s performance and lower the motorcycle’s MPG.
See article: How is motorcycle fuel consumption calculated?
However, running one tank of a 110 octane fuel without modding your Harley will usually not hurt the engine in any way. But if you plan on running 110 octane regularly, it is recommended to adjust the timing and compression to really take advantage of the higher-octane fuel and prevent damaging the engine in any way.
Is it worth using 110 octane fuel in your Harley?
Overall there is no real reason or benefit in using 110 octane fuel in your Harley if you are not going to tune it properly. Not only can a higher octane fuel negatively affect the motorcycle’s performance, but it can also lower the fuel efficiency.
Thus in the majority of cases using 110 octane fuel will be a waste of money, as 110 octane fuel is usually more expensive than regular fuel and provides no real benefit.
Race fuel (100 to 110 octane and higher) should be reserved to race motorcycles or motorcycles with high compression engines.
The best power to performance ratio is usually achieved with the lowest octane fuel that does not produce pinging or preignition. If you are running stock compression and timing, there really is no need to use 110 octane fuel—especially, if you only use your motorcycle for the street.
Since most Harleys today are recommended to run on 91 octane fuel or higher, the 91 to 93 octane range is considered the best.
That being said, most riders will agree that 110 octane does smell really good.