The question of the compatibility of different types of lubricants for two-stroke engines arises with enviable regularity among owners of outboard motors, snowmobiles and chainsaws, the situation when there is a little mineral oil in the tank and semi-synthetics is splashed in the canister, is familiar to many boaters. Often at such moments, a hasty decision is made to add what is at hand, without thinking about the chemical processes that can start in the fuel mixture.
Modern two-stroke engines, especially outboard motors boat-engineThey require extremely precise oil-gasoline ratios to work properly. Violation of the proportions or the chemical composition of the mixture can lead to piston rings coking, overheating and even cylinders being bullied. Understanding the difference between the basic oil bases is a key factor in the durability of your engine.
In this article, we will examine in detail the chemical features of mineral and semi-synthetic compounds, explain why mixing them can be dangerous, and answer the most common questions of owners of equipment. 2T engines.
Chemical composition: mineral base against semisynthetics
To understand the risks of mixing, you need to understand the origin of the base oils. Mineral oil It's a natural product that contains complex hydrocarbons, sulfur and other impurities that are not always completely removed during refining, and its molecular structure is heterogeneous, which affects the stability of viscosity as temperatures change.
Unlike the mineral water, semisynthetic oil The synthetic part, often created by hydrocracking or polyalphaolefins (PAOs), has more stable specifications, is better at resisting oxidation and retains its properties in extreme working conditions. two-stroke.
The main difference is the additive package: mineral oils are added more detergents and dispersants to compensate for the poor quality of the base base. Semi-synthetics require fewer additives because the base is cleaner. When these two types are mixed, additive chemical conflict can occur, leading to precipitation.
⚠️ Warning: Chemical incompatibility of additive packets can lead to the formation of a jelly-like substance that will clog the fuel filters and jelly-like carburetor.
What is hydrocracking?
Hydrocracking is the process of deep purification and modification of the molecular structure of mineral oil under high pressure of hydrogen. The resulting base (Group III) is similar in properties to synthetics, but cheaper to produce, and it is these oils that are often labeled as semi-synthetics or even synthetics (VHVI).
Why do you want to mix different oils?
Most often, mixing is not from the good life, but from the banal lack of material at a critical moment. A boater may find that literally 100-200 grams of mixture is missing to complete the trip. A faraway store, and you need to swim, and then the idea comes to mind to dilute the remains of the mineral water with the available semisynthetics.
Another reason is to save or improve the properties of cheap oil, and some users mistakenly believe that adding expensive semi-synthetics to a cheap mineral water will "enhance" its specifications by making the mixture more temperature-resistant, a dangerous misconception, since the properties of the mixture are determined by the worst component.
Also, there is a situation with the injection of lubricant into the tank separately (for motors with a separate oil tank). 2T If you've been poured before, it can add the first thing you get, and it creates a cocktail, and the chemical composition of it is unpredictable, and it can range from the working mixture to the abrasive porridge.
Technical consequences of mixing the bases
The first and most noticeable consequence of mixing oils with different bases is a change in viscosity specifications. Viscosity The oil is the ability to resist flow, mineral oils become thinner when heated than synthetic components, and the mixture can be dissected or unevenly distributed viscosity, leading to oil starvation during peak stresses. crank-and-shifter.
The second critical point is the formation of sodium. Mineral oils tend to produce more solid deposits when burned. Semi-synthetics burn cleaner. However, when mixed and heated, the combustion chamber can produce sticky, hard-to-remove sodium. piston, rings and exhaust window, reducing compression and engine power.
The third aspect is the lubricating ability of the film: Two-stroke engines work in conditions where the oil burns with the fuel; the film must be very strong to protect the crankshaft bearings; Mixing the bases can disrupt the adhesion of the oil to metal surfaces, which will lead to accelerated wear of rubbing vapors.
| Parameter | Mineral oil | Semi-intelligent | Mixing result |
|---|---|---|---|
| Flash temperature | Low/Medium | High. | Unstable, risk of detonation |
| ash | High. | Low/Medium | Increased candle-on-candle scoring |
| Solubility in gasoline | Good. | Great. | Possible mixing |
| Storage period of the mixture | Up to 2 weeks. | Up to 1 month. | Dramatically reduced (oxidation) |
Impact on the operation of the outboard motor
For outboard motors, which often operate in full load mode (planing), the quality of the lubricant is critical. The mixture of oils can lead to unstable operation at idle speeds. The engine can stall or "float" in revolutions due to changes in the quality of the fuel-air mixture and variations in oil combustion.
Overheating is particularly dangerous. Two-stroke engines It's cooled in part by purging and evaporating the fuel mixture, and if the mixed oil doesn't burn completely or with insulating soda, the heat sink gets worse, and that's a direct route to overheating the cylinder head and deforming the piston partitions.
Also worth mentioning are spark plugs: The wrong oil mix often causes the candle electrodes to quickly form a fur coat, the candle stops sparking, the engine troizes, and in water conditions, it can result in loss of stroke and the need to tow, which is always unpleasant and unsafe.
If you still mixed the oils and the engine works, try to develop this tank at minimum speeds and without sharp openings of the throttle, so as not to create peak loads on the CNG.
Manufacturers’ opinions and API/TC standards
Engine manufacturers, such as Yamaha, Tohatsu, Mercury and SuzukiIn the instructions for operation it is strictly not recommended to mix oils of different types and brands. API TCThe slurry, which is the main one for high-load two-stroke engines, requires a clear matching of the composition to certain parameters.
Manufacturer engineers test their engines on specific types of oils. Warranty obligations can be waived if the examination shows that the failure occurred due to the use of poor-quality or mixed lubricants. The logic of manufacturers is simple: it is impossible to predict the behavior of a chemical cocktail, so it is easier to prohibit.
There are oils that are labeled as "universal" or compatible with all types, but even so, manufacturers advise avoiding constant mixing: A single emergency topping is less scary than constant operation on a mixture of different bases.
⚠️ Note: The use of a mixture of oils in a new engine during the break-in period is strictly prohibited, this is guaranteed to lead to improper laundry of the rings and a decrease in engine life.
Algorithm of actions if necessary mixing
There are times when you don't have a choice, and if you're away from civilization and you're wondering if you need to add some other oil to get to the base, or if you need to get up and wait for help, you choose the former, but you need to do it wisely, minimizing the risks.
The first thing you need to do is to try to empty the tank of the old mixture as much as possible, if possible, or at least understand the proportions. If you mix oils in a gas tank, shake the tank carefully. For two-stroke engines, it is important that the oil is evenly distributed in gasoline before being fed into the carburetor.
After the mixture is produced, maintenance is strongly recommended, including replacement of the spark plug, compression check and visual inspection of the piston through the candle hole (if possible), and it is also useful to rinse the fuel system with pure gasoline before filling with quality oil.
☑️ Actions after mixing oils
How to switch from one type of oil to another
If you're going to change the type of oil (e.g., switch from mineral water to semi-synthetics to improve performance), you have to do it right. Just add new oil to the old one is a bad idea. The best way is to completely develop the old fuel mixture to a dry tank.
Once the engine has stalled due to lack of fuel, you can fill a new mixture with a new type of oil. In the case of engines that have a separate oil tank, it is better to pump out the old residue with a syringe or pear so that it does not mix with the new canister.
It is critical not to mix oils of different colors and manufacturers in large volumes in advance. The chemical reaction between different brands can start instantly, and by the time you pour into the tank, you'll have a product with altered properties.
Full production of old fuel is the only safe way to switch to another type of oil without washing the engine with special compounds.
Frequently Asked Questions (FAQ)
Can you mix mineral water and semi-synthetics if they are the same brand?
Even if the brand is the same, the basics may differ, the manufacturer may use different additive packages for different product lines, and although the risk of chemical conflict is lower than that of different brands, the specifications of the mixture will still be averaged for the worse, and this can only be done in an emergency.
Will the boat's performance on mixed oil deteriorate?
Perhaps because of the change in the octane number of the mixture (oil affects knock resistance) and the quality of combustion, the engine may be less stable, you may notice a loss of thrust at high revs or increased fuel consumption.
How long can you operate the engine on a mixture of oils?
Only until the nearest opportunity to drain the tank and refuel with the right mixture. Prolonged operation (more than one tank) in a mixture of mineral and semi-synthetic oils is not recommended, since the risk of coal and exhaust windows coking increases exponentially.
Do I need to flush the engine if I accidentally mix the oils?
Special washing is usually not required unless there was any sign of overheating or knocking, just make a mixture, replace the candle and then use only the manufacturer's recommended oil, and the engine will self-clean itself in the process of normal operation on the right fuel.