Whats the difference between 4 stroke and reg motor oil?

Owner manual to boat calls for 4 stroke oil. 10/20 weight. Salesman says regular motor 10/30 or synthetic 10/30 is same.Whats the difference between 4 stroke and reg motor oil?
Very simple answer, noneWhats the difference between 4 stroke and reg motor oil?
Four stroke is the same type of oil you would use in your car. It remains in the motor for lubrication.





Traditional boat motor oil is a 2 cycle (or 2 stroke) motor oil that is meant to be mixed with the gas or directly injected into the combustion chamber and burned with the fuel. In a boat with a two-stroke motor you must add oil to an oil tank (or mix with the gas) on a regular basis as it is burned up as the motor runs.





2-Cycle boat oil usually has a TC-W3 designation whereas the 4-stroke oil generally has regular car designations like 10W-30.





YOU MUST USE THE RIGHT ONE depending on whether you have a two-stroke or four-stroke. If it's a four-stroke the motor will usually have a label on the side of the cowling saying ';four stroke';. Also a four stroke will have a dip stick in the engine compartment like a car.





Synthetic is not exactly the same as regular in their chemical composition but can be used in the same way. For example if your motor requires 10w-30 then you can use either 10w-30 in regular oil and/or 10w-30 in synthetic (unless the motor specifies synthetic only). Synthetic is more expensive.
A lot of boat motor are two stroke engines and they mix the oil and the gas together to run the engine,,,and there is no oil pan,dip stick etc. It uses what is called 2 stroke oil and its specially made to mix with gasoline and be burned by the engine.


If you have a four stroke engine then you DO NOT mix the oil with the gasoline. There is some sort of oil pan etc,,,like a car. It uses regular car type engine oil.
A good quality regular 10w/30 oil should be fine. Make sure that it meets or exceeds OEM requirements for your engine, not sure if you have a warranty but you need to meet API Service Classifications so it will not void engine warranty.





You are smart to question the salesman, some boat salesmen only know enough about boats to complete the paper work. Some are very nautical smart and will steer you right. But that is another subject.....
If the manual calls for 10w 20, thats what you need. It can be ';regular '; motor oil as long as it meets the current SAE specs. 10w 20 is not the same as 10w 30 as far as weight is concerned, but you should be able to find it in the auto store.
about 3 dollars a gallon