I am a strong advocate for use of synthic oils. Yes they do extend change intervals providing you do one thing. Regularly change the oil filter
and most importantly use a very high quality filter. It is the filter that is the difficult part. Donaldson make very high quality filters and Amsoil have very high quality filters made for them. The filter needs to be two things. A very fine filtration, down to 2microns for Amsoil and a very high capacity, or surface area. It's no good capturing finer particles if it means the filter blocks up quicker. It also makes no sense in enjoying the longer life of the oil, if you are going to wave savings with that against the cost of many times more filter changes over the extended life.
The negative issues are found mainly in very worn engines. Sometimes it is the crud that is actually keeping the engine working. Putting in a synthetic can in these instances, cause the engine to start leaking and even fail, due to the fact that synthetics have excellent detergent properties and will break down the sludge and clean it away. However, if your engine is that bad, it is in dire need of overhaul
anyway and should never be relied upon in a boat.
Whether you use synthetics or not, the regular change of filters and the use of a good quality one at that, is equal to the quality of the oil. However...
Synthetics give you several advantages over regular Dino oil. Firstly is the extended change interval. Some engines have been fitted in such away, that oil change
is difficult at best. I am sure I have many echoing my feeling when it comes to change time.
Synthetics usually have a characteristic of having a thin film that clings to all metal surfaces when the engine has stopped. This helps reduce internal corroison of parts
, especially the highly polished ones like cam surfaces and the different metals combination of piston rings and cylinder bores. Plus the film helps lubricate till oil pressure reaches all the nooks and crannies when the engine is started again.
Synthetics remain stable for a greater period of time and can deal with acid build up in greater quantities for longer. This is one of the biggest factors in changing oil, is to get rid of the impurities that no amount of filtration can remove.
And of course, better protection form high moisture contents, especially for parts below waterline that have seals
to keep the water
out and the oil in. Synthetics can still have lubricating properties when highly contaminated with water
when Dino oil has long scince drowned.
life and performance can be greater enhanced with synthetics. They often run cooler and this greatly enchances there life.
HOWEVER!!! just like all things, not all synthetics are created equal. So beware of what you put in.
AND EVEN MORE IMPORTANTLY!!! NEVER EVER put additives in to ordinary oil to try and raise it's quality. At least that is my personaly view.