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Oil Injection vs. Premix: Which is Better on a Jet Ski? [Comparison]
Last Updated on
The oil injection vs. premix debate is one of the biggest arguments in the 2-stroke jet ski community. While some owners are happy with their oil injection system, others bypass it and mix the fuel manually for safety reasons.
Are you wondering which is the best on a jet ski, oil injection or premix? Without further ado, here are the main pros and cons on each side:
Benefits of Premix:
- Safer – Less risk of engine seizure
- Control over the mix ratio (great for racers and stand-up riders)
- Easier maintenance
Benefits of oil injection:
- Far more convenient (no hassle of premixing)
- Easier to refuel
- Variable-rate injection (depending on the model)
- Lower oil consumption
- Less smoke
- Fewer risks of fouled spark plugs and starting issues
- It’s required on most fuel-injected engines
If you want to drill into the details, keep reading. We at JetDrift have compiled all you need to know under one roof!
Benefits of Premix
There’s no question that the main advantage of bypassing the oil-injection system and using premix is that it ensures that your engine is lubricated at all times.
Oil-injection system failure is common on 2-stroke jet skis, which usually means an instant engine seizure.
But contrary to popular belief, it’s not the oil pump that fails in most cases. Instead, the oil lines are prone to aging and cracking. In other cases, they just fall off and pump oil into the bilge instead of the engine.
Whatever the cause of the failure, this leaves the engine without lubrication, leading to a seized engine. And an engine rebuild on a jet ski is a pretty expensive service!
To avoid these issues, many owners decide to remove the oil-injection system on their jet skis and mix the fuel manually. As they say, running on premix is like having a second insurance policy on your ski.
If your jet ski is oil injected, there’s no way to tell if this system is working and how much oil is getting mixed into the gas. All you can do is keep your eyes on the spark plugs, oil lines, the amount of oil in the reservoir, and hope for the best.
Since you never know when the oil-injection system will go bad, using premix is the only way to guarantee your engine is getting oil at all times.
Control Over the Mix Ratio
If your jet ski is oil injected, it means the mix ratio of the fuel depends on the oil pump.
While it’s efficient and convenient for recreational riding, an aggressive riding style may require unique mix ratios.
General wisdom ways that premix is recommended for closed-course racers and stand-up riders while average riders can’t go wrong with the mix ratio provided by an oil-injection system.
Using premix also results in easier maintenance as you don’t have to check and work on the oil-injection system.
It’s common knowledge among riders that the oil injection system can go wrong in many ways, but the leading reason for failures are broken oil lines. These rubber hoses are prone to clogging, cracking, or simply falling off.
Because of this, the entire oil-injection system requires continuous attention and care. It’s also wise to periodically replace the oil lines regardless of their condition.
Besides the hoses, you also have to keep your eyes on the pump, the oil reservoir, the in-line oil filter, and the oil pump cable (if featured).
If you switch to premix, you don’t have to deal with these systems.
Also, don’t forget that you have to keep a sufficient amount of 2-stroke oil in the reservoir to avoid oil starvation issues. This is why manufacturers recommend checking and refilling the oil tank every time you refuel your jet ski.
Benefits of Having Oil Injection on a Jet Ski
Let’s face it, mixing gas with oil in a separate gas can before you pour it into the tank is always a big hassle.
It’s exhausting, messy, and requires a lot of attention, and if you mess up the ratio, you can easily mix the fuel so it’s too strong or too weak.
While the former only results in a lot of smoke and fouled spark plugs, running lean can lead to overheating or even permanent engine damage.
This is why oil-injected jet skis are so popular. The oil-injection system literally does the dirty work for you as it’s intended to mix the oil into the gas.
You don’t have to be afraid that the mixture ratio is wrong or manually create the premix. All you need to do is regularly refill the oil reservoir and pour gasoline directly into the fuel tank.
Easier to Refuel
If your jet ski runs on premix, it means that you have to manually mix the fuel every time before you refuel. While this may be fine if you play around near the shore, it can be a huge hassle on long tours.
This is because if you can’t carry all the required premixed fuel on your jet ski, you will have to refuel it on the water. And keep in mind that pouring 2-stroke oil into the fuel tank along with gas, then “shaking” the jet ski is not a good idea!
The only way to properly refuel a 2-stroke jet ski is to mix the fuel upfront in a gas can, then pour the mixture into the fuel tank. As you can imagine, it’s not convenient nor safe when the jet ski is floating on water.
What’s more, you also have to carry a bottle of oil on you, which takes up space in the storage bin. And you will also need an empty gas can for this purpose.
In contrast, a fuel-injected 2-stroke jet ski can easily be refueled even at a fuel dock, just like its 4-stroke counterparts.
If you don’t make long trips and typically ride in the same spot, the level of inconvenience depends on what your boat ramp or dock is like.
If you have to refuel, you have to get back to your car for the gas can and the oil. If you have to park far away from the dock, refueling with premix can be a hassle.
Variable Mix Ratio
As a rule of thumb, 2-stroke jet skis were manufactured with two different oil pump designs.
The early models featured a “static” oil pump that metered the same amount of oil regardless of engine speed.
In contrast, later models were manufactured with variable oil pumps linked to the throttle lever via a cable. The more throttle you apply, the more oil the pump forces into the engine.
This advanced design has many advantages, which we will go through in detail below.
The key advantage of a variable oil-injection pump is that it provides more lubrication at higher RPMs while it keeps the fuel lean while idling around.
As a rule of thumb, an oil-injected jet ski runs on about 30:1-40:1 mix at WOT, but it leans the fuel out to about 100:1-300:1 while idling. (The exact mix ratios vary widely depending on the model and features.)
This flexible system improves oil efficiency as your jet ski won’t unnecessarily burn much oil while idling or running at lower RPMs.
Less Smoke and Fouled Spark Plugs
Another key advantage of having a variable oil pump on a jet ski is that it ensures less smoke while idling. What’s more, it also helps avoid fouling spark plugs!
If you switch to premix, your jet ski will run on 40:1 -50:1 at all times (depending on your preferred mixture ratio). This means that the mixture will be too rich for idling.
Excessive oil in the cylinders can generate a ton of smoke and foul the spark plugs, which translates to starting issues or unexpected stops on the water. This could be an issue in no-wake zones and around the dock, where you can only go at idle speed.
Since static oil pumps on the oldest vintage jet skis meter the same amount of oil at all times, they too can cause the symptoms mentioned above.
Oil Injection is Required on Most Fuel-Injected Jet Skis
It’s also good to know that most fuel-injected 2-stroke jet skis can’t run on premix.
The injectors on 2-stroke fuel-injected Yamaha WaveRunners are in the air intake, so these machines can be premixed.
Regarding other manufacturers, on Polaris Ficht Direct Injection engines, Sea-Doo Di and RFI engines, as well as Kawasaki DI engines, the oil-injection systems can’t be removed.
This is because the injectors are planted on top of the cylinders, so premixing these machines would leave the bottom end without any lubrication.
Conclusion on Oil Injection vs. Premix
Which is better, oil injection or premix?
It seems there’s no clear winner here, as there are many pros and cons on each side!
Many riders say that premix is the only way to go. It’s far safer as you don’t have to be afraid of an oil-injection system failure.
It also gives you control over the mix ratio, a key advantage for racers and stand-up riders. On top of that, the lack of an oil-injection system also means easier maintenance.
Others argue and claim that an oil-injection system is essential on any 2-stroke jet ski. It’s much more convenient to pour oil into the reservoir than having to premix the fuel before each ride, isn’t it?
Refueling an oil-injected jet ski is always much easier, especially on the water.
Variable-rate oil pumps also ensure lower oil consumption as they lean out the fuel at idle speed. This feature results in less smoke and fouled spark plugs. Starting oil-injected jet skis is always much easier, faster, and cleaner.
Surprisingly, many owners decide to reinstall their oil pumps when they get tired of dealing with starting issues, fouled spark plugs, and massive smoke!
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