What is the difference between car oil and boat oil?

I know they are digferent colors and everyone uses them but why? With the antifreeze it is obvious that useing a non-toxic item would be desirable, but with oil it is contained. I want to use Mobil 1 or Ames with some Slick 50 instead of this marine oil, should I?What is the difference between car oil and boat oil?
I've used and` recommended Synthetic motor oil as a marine mechanic, in marine applications, since 1983. It is superior to most petroleum based oils. I now use a 20W-50 and run it 500 Hr. between changes. If you repair engines, you can see the results. Mercrusier and Volvo now recommend synthetics. What is the difference between car oil and boat oil?
Depends on the motor. Most inboard/outboard marine engines require straight 30 SAE, where cars require 5/30 or 10/30.


The difference is the viscosity of the oil and the thermal breakdown. Marine engines usually require a heavier weight engine oil because of the constant higher RPMs the engines operate at, typically around 3500-4000rpms where as car engines vary the rpms greatly and operating conditions, and need a lighter oil.
What you need to do is find out what weight and SAE rating your engine manufacturer states you should use. the temperature range where you operate will determine if you are using a multi grade oil or not ( like 30w or 15w-40). If you are down in Florida you might be able to use a straight weight oil like 30w, but in the North you will need a multi weight to deal with the temperature swings. The SAE rating would be an ';S'; rating for gas engines and a ';C'; rating for diesels. Gas ratings might be SF-SG and diesel may be CD-CE. These ratings are changed as different additives are added to the oils allowing a change in operating conditions. So for a gas engine you might be looking for the markings ';SAE 15w 40'; and ';SF-SG'; on the can. It makes no difference who makes it as long as it meets those requirements. Manufacturers will try to get you to use their ';branded oil'; but can't make you do it for any reasons. I know people that swear by synthetic for its longer life but I have a problem keeping that oil in the engine for what would be a few years on my boat. If your engine company says to use 10w-30, thats the weight you should use. Check and see what service rating they say to use. Remember as the oil is improved (like SC to SD) it meets or exceeds the previous generation oil but the previous generation does not meet the new one.
The difference in the oil types is the additive package they use for marine engines.As I am sure you know a marine engine is always reving at a higher rpm so they need additives in it that will not break down.You can use Mobil 1 or Ames,they are a good quality oil.You can use any type oil you wish as long as it is of good quality and will


not break down easily.Hope this helps.
Not much difference. If your boat engine is an enclosed engine then no difference.


However. If you have a little outboard engine that requires a mixture of oil and gas then you should follow the instructions carefully.





Don't mix diesel oil with gasoline oil. Bad. In a pinch it will do but not on a full time basis.





It would be best to find out the requirements of your particular engine. And use the best oil that you can afford. Trust me on that one after an expensive bill.
same stuff oil is oil in a inboard engine
There is no significant difference. Apart from the already mentioned two stroke engines, which require their own particular type of lubricant there is no engineering principle other than the engine makers specification that is relevant.





While an older engine may have had a particular grade of oil like 'SF' specified, a modern grade like 'SJ' will be fine, as long as the specified weight of the oil is adhered to. After all the precise wording will almost always be ';..meets or exceeds the following grade...';





If the original specifications demand a 20W 40 mineral oil you should not substitute a 10W 30 synthetic in it's place.





Marine engines will normally work in a more stable and limited temperature range compared to air cooled engines (even those relying on radiators such as your car are ultimately air cooled, The coolant is just an efficient way of getting the heat out of the engine). This allows the maker to fine tune the engine to have a narrow tuning range, and to often specify mono-grade oils - particularly for commercial applications.





The reason for multigrades is generally most obvious when cold starting an engine. Lighter oils when cold allow the engine to be turned over faster, and also flow through the oil galleries much quicker to minimise the potential of dry running in the first moments of start up (when 90% of the wear happens). As the engine warms this rapidly turns to a problem as the oil becomes too thin, polymer additives are used to cause the oil to significantly thicken as it gets warmer thus allowing the engine again to receive minimal wear. The oil does not 'wear out' but the additives do, and are the main reason beside combustion by-products and fuel contamination for changing your oil. Hours of use is one thing, but the quickest way to degrade the oil is sporadic and intermittant use, which never allows the oil to acheive true operating temperature and will result in acid build up in unused engines treaded like this. It is why you store an engine with new oil in it.





The specified 10w 30 is suitable for use down to +5 C, your manual will clearly show the various grades required for a given temperature range and you cannot go wrong if you follow the makers reccomendations.





I am ambiguous about additives. I have tried several over the years but am a little wary as some of the results were not quite those suggested - I am impressed at 500 hour service intervals, on my machinery that is the same as 50,000 kms in your car. I would find that just too long for me.