Good Gas vs. Bad Gas: What Should You Put in Your Motorcycle?
Motorcyclists spend plenty of time debating oil, tires and performance upgrades, but we often pay much less attention to what goes into the fuel tank. That is a mistake.
Your motorcycle’s fuel quality can affect throttle response, starting, fuel economy, engine temperature and long-term reliability. This is especially important for motorcycles because they have relatively small fuel tanks, frequently sit between rides and often operate in demanding conditions.
So, what qualifies as good gas—and what should riders avoid?
Start With the Octane Grade Your Motorcycle Requires
Octane measures gasoline’s resistance to premature combustion, commonly called knocking or detonation. It does not measure the fuel’s cleanliness, energy content or overall quality.
In the United States, the most common grades are:
Regular: 87 octane
Midgrade: 89 octane
Premium: usually 91–93 octane
The correct grade is the one specified in your motorcycle’s owner’s manual. If your motorcycle requires premium fuel, use premium. High-compression and air-cooled engines can be especially sensitive to detonation, particularly during hot weather, heavy acceleration, two-up riding or when climbing steep grades.
Many Harley-Davidson motorcycles, including Milwaukee-Eight touring models, call for 91-octane or higher premium unleaded gasoline. Owners should confirm the requirement for their exact year and model.
Using 87 octane in an engine designed for premium might save a few cents at the pump, but it can contribute to pinging, reduced performance and the engine management system pulling ignition timing.
On the other hand, putting 93 octane into a motorcycle designed for 87 will not automatically produce more horsepower or make the engine run cleaner. Higher octane is beneficial only when the engine needs it.
The rule is simple: Use at least the octane rating required by the manufacturer. Going lower can create problems; going higher usually provides little benefit unless the engine is tuned for it.
Octane and Fuel Quality Are Not the Same Thing
One of the biggest misconceptions about gasoline is that premium automatically means better-quality fuel.
Premium describes the octane rating. Fuel quality depends on several additional factors:
The type and concentration of detergent additives
The freshness of the fuel
Proper station-tank maintenance
Water or sediment contamination
Ethanol content
How long the fuel remains in your motorcycle
You can buy 93-octane gasoline with only the minimum federally required detergent package, or 87-octane gasoline carrying the TOP TIER designation. The first has greater knock resistance, while the second may contain a more effective detergent package.
Your motorcycle may require premium, but you should still look for premium from a clean, busy and reputable station.
What Is TOP TIER Gasoline?
TOP TIER is a fuel-performance standard supported by major engine and vehicle manufacturers. It requires gasoline to meet standards for controlling deposits on fuel injectors, intake valves and combustion chambers.
This is not the same thing as premium-grade gasoline. At a TOP TIER-approved retailer, all gasoline grades sold under the approved brand must meet the detergent standard.
According to the TOP TIER program, an AAA study found that qualifying gasoline produced dramatically fewer engine deposits than lower-detergent fuel under the conditions tested. That does not mean every non-TOP TIER gallon is harmful, but it provides a useful quality standard when choosing between stations.
Look for the official TOP TIER logo on the pump, canopy or station window. Because participating brands can change, riders can confirm the current list using the official TOP TIER station finder.
Some of the Best Gas Brands for Motorcycles
Rather than choosing a brand because of advertising alone, I recommend selecting a current TOP TIER-approved brand at a busy, well-maintained station.
Commonly available choices may include:
Chevron
Shell
Exxon
Mobil
QuikTrip
Costco
Phillips 66
Conoco
76
Citgo
Sunoco
Marathon
BP or Amoco
Sinclair
Brand participation and regional availability can change, so verify the TOP TIER logo rather than relying solely on an old list.
Chevron and Shell are especially popular among riders because of their established detergent packages. Exxon and Mobil are also widely available and convenient during long-distance trips. In the Southeast, QuikTrip is often a strong choice because its stations generally have high fuel turnover.
Costco can provide excellent fuel at a competitive price, but you may not always find a location convenient while traveling on a motorcycle.
The logo on the canopy is only part of the decision. A busy, clean station with modern pumps and frequent deliveries is usually preferable to an isolated station selling very little premium fuel.
Which Gas Brands Should You Avoid?
There is no responsible way to declare that every station belonging to a particular national brand sells “bad gas.” Fuel is frequently transported through shared pipelines and terminals before each company’s additive package is blended into it. Individual station maintenance and fuel turnover can matter as much as the name on the sign.
Instead of maintaining a brand blacklist, avoid stations showing these warning signs:
The station appears poorly maintained.
Pump seals are broken or inspection stickers are outdated.
Water, dirt or debris is visible around the fuel-filling area.
The station has very little traffic or premium-fuel turnover.
The fuel truck is actively filling the underground tanks.
The pump is unusually slow or repeatedly shuts off.
The price is suspiciously lower than every nearby station.
The gasoline smells, looks or behaves unusual.
You have previously received contaminated fuel there.
When a tanker is filling a station’s underground storage tanks, the incoming fuel can stir up sediment and water lying near the bottom. Modern filtration systems are designed to catch contamination, but I still prefer to fuel elsewhere or return later.
Unknown independent stations are not automatically bad, and name-brand stations are not immune from problems. When traveling, however, a busy station operated under a recognized TOP TIER brand generally reduces the gamble.
Freshness Matters More to Motorcycles
A car may burn through a tank of fuel every week. A motorcycle might sit for several weeks—or all winter—with only a few gallons in the tank.
Gasoline begins changing as it ages. Its lighter components evaporate, oxidation occurs and deposits can develop. Ethanol-blended fuel can also absorb moisture from the surrounding air. If enough water enters the fuel, phase separation may occur, leaving an unfavorable alcohol-and-water mixture near the bottom of the tank.
That is one reason a busy station matters. High turnover usually means the fuel has spent less time sitting in the underground tank. This is especially relevant when buying premium because some rural stations sell far less premium than regular.
Once fuel is in your motorcycle, avoid letting it sit untreated for extended periods. If the bike will be stored, use a dedicated fuel stabilizer according to its label and ride the motorcycle long enough to circulate treated fuel through the entire system.
Be Careful With Ethanol Content
Most motorcycles are designed to operate on gasoline containing up to 10% ethanol, commonly labeled E10, but always check the owner’s manual.
Avoid these fuels unless your motorcycle’s manufacturer specifically approves them:
E15 or Unleaded 88
E30
E85
Flex Fuel
Racing fuel containing additives unsuitable for street engines
Leaded gasoline
E15 contains between 10.5% and 15% ethanol. Federal guidance does not approve it for motorcycles, and using it can create compatibility, drivability and warranty concerns. The U.S. Department of Energy provides additional information about E15 and the vehicles approved to use it.
Ethanol-free gasoline can be a good option for motorcycles that are ridden infrequently, small engines and older motorcycles with fuel-system components that are less tolerant of alcohol. However, ethanol-free fuel is not automatically cleaner or better. It still needs the proper octane rating, and it should come from a busy, reputable station.
For a modern motorcycle ridden regularly, fresh E10 from a quality station is normally preferable to old or questionable ethanol-free gasoline.
Why Use a Fuel-System Cleaner Even When Buying Good Gas?
Good TOP TIER gasoline helps prevent deposits, but it cannot control every factor affecting a motorcycle’s fuel system.
Motorcycles operate under conditions that can still encourage deposits:
They may sit for days or weeks between rides.
Heat from the engine can affect fuel in the tank and lines.
Small injectors have extremely fine passages.
Fuel repeatedly heats and cools during short rides.
Riders cannot always find their preferred gasoline while traveling.
An occasional questionable tank can happen to anyone.
Existing deposits may have developed before you began using better fuel.
A quality fuel-system treatment provides a concentrated cleaning dose that can help remove deposits from injectors, carburetors, intake valves and combustion chambers. It can also help maintain throttle response and reduce deposit-related hesitation or rough running.
That is why I believe occasional treatment makes sense even if you normally purchase good gasoline. Think of TOP TIER fuel as regular housekeeping and a quality cleaner as periodic deep cleaning.
My Choice: Red Line 60102 Powersports Fuel System Cleaner
One treatment worth considering is Red Line 60102 Complete Powersports Fuel System Cleaner. It is formulated specifically for motorcycles, ATVs, personal watercraft and other powersports applications.
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Red Line says the product is designed to clean:
Fuel injectors and carburetors
Fuel lines and tanks
Intake valves
Combustion chambers
Fouled spark plugs
It is also marketed as safe for modern catalytic converters and oxygen sensors and compatible with pump gasoline, racing fuel and certain two-stroke applications.
Even if you consistently buy premium TOP TIER gasoline, this treatment can be useful because it provides a more concentrated cleaning cycle. It may be particularly worthwhile:
Before or after a long motorcycle trip
After receiving questionable fuel
When the motorcycle has spent considerable time sitting
If throttle response or idle quality begins declining
As periodic preventive maintenance
When buying a used motorcycle with an unknown fuel history
For a quick cleanup, the product directions call for pouring one 4-ounce bottle into the motorcycle’s fuel tank before filling it. Always follow the directions printed on the bottle you purchase because formulations and instructions can change. More is not necessarily better, and fuel cleaner should not be added to every tank unless the manufacturer recommends that frequency.
Fuel-system cleaner should not be confused with fuel stabilizer. A cleaner targets deposits, while a stabilizer slows fuel deterioration during storage. Some riders may benefit from both products, but each should be used for its intended purpose.
What a Fuel Treatment Cannot Do
Fuel additives are maintenance products—not bottled repairs.
A cleaner will not fix:
A failing fuel pump
Rust or severe contamination inside the tank
A physically damaged or completely blocked injector
Deteriorated fuel hoses
Incorrect ignition timing
Worn spark plugs
Low compression
Electrical or sensor failures
If your motorcycle is hard to start, stalls repeatedly, loses significant power or produces unusual noises, diagnose the underlying problem instead of repeatedly adding chemicals to the tank.
The Bottom Line
The best gasoline for your motorcycle is:
The octane grade required by its manufacturer
Purchased from a TOP TIER-approved brand when available
Dispensed by a clean, busy and well-maintained station
Fresh and within the motorcycle’s approved ethanol limit
For many modern Harley-Davidson motorcycles, that means fresh 91- or 93-octane premium from a busy TOP TIER station.
Avoid questionable stations, stale fuel and high-ethanol blends not approved for motorcycles. Use a dedicated stabilizer when the bike will sit, and consider periodic treatment with a reputable powersports fuel-system cleaner such as Red Line 60102—even when you normally buy good gasoline.
Premium fuel cannot correct poor maintenance, and a bottle of cleaner cannot repair a damaged fuel system. But when you combine the correct fuel, a trustworthy station and sensible preventive maintenance, you give your motorcycle a much better chance of starting easily, responding cleanly and carrying you reliably through the miles ahead.
Until next time…
Ride safe. Ride smart. Trust God.
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