Yes, there are many benefits of using synthetic oil.
There is the base oil and the additive packages like viscosity modifiers, detergents, anti-foaming agents, corrosion inhibitors, friction modifiers etc..
Crude oil is a mix of of hydrocarbons ranging from the lightest fractions like pentane, octane etc, which are typically used as fuels, solvents etc.. down to the heavy fractions like Bitumen (asphalt) and heavy bunker oil (which is so heavy that it has to be pre-heated before it can be pumped in to say, a ship-engine)
In addition to the different sizes of hydrocarbons, there are a multitude of different molecular "configurations" of the hydrocarbon molecules, Alkenes, Alkynes, Cyckloalkanes, etc. plus impurities like sulfur etc as well as waxes and asphaltenes. An interresting mix to say the least.
The crude is separated in to different weights and species through various refinery processes. lubricants come out as everything from the lightest oils just below diesel, to heavy greases just above the heavier bunker grades.
Base oils used in engine lubricants are found inbetween here depending on weight and intended usage.
Even though the crude is refined in to many different fractions, a base oil will allways be a mix of a "range" of different species and weights of hydrocarbons.
True synthetic base-oils are, as the name implies, made from synthesizing oil molecules through various chemical processes, just like polymer (plastic) molecules are synthesized from high purity light hydrocarbon base stock or other chemicals.
This means that a synthetic base oil will have a much more uniform composition of hydroocarbons most desireable.
The end result is usually better resistivity against breakdown from heat and oxidisation (which changes the properties of the oil and causes gum and coke deposits), less evaporation of lighter fractions under heat, better viscosity stability, more stable and predictable load-bearing capacity etc.. all the good thigs you want from a good oil.
The additive packages are another business alltogether, but that is more down to brands of oil than synthetic or mineral as such.
So, is synthetic oil worth the extra cost?
Yes and no.
On new engines with long oil change intervals and tight clearances etc, the improved long term stability of synthetics are sometimes a must.
I don't believe in long oil-change intervals. there is allways a buid up of soot particles, corrosive combustion by products, moisture etc. Some oils cope better with this than others, but the best way to deal with these nasties, are to get rid of them, i.e. change the oil.
The second best option, is frequent oil and filter change with a decent mineral oil.
The best option, is frequent oil and filter change with a decent synthetic oil.
By changing the oil more frequently, you don't really need the more exotic and expensive brands with a high tech additive package required for coping with long shift intervals.
So what is a decent synthetic oil?
Well, this can be difficult to positively identify as specifications are not allways widely available, and if found you need to have som sort of idea what they actually mean.
From the "research" and comparisons I've done, I have found that price and brand does not allways correlate with certain qualitative indicators.
The fact remains however, that there are fewer refineries and hydrocarbon synthesizing plants than there are brands out there, i.e a lot of the base oils, or even the finished base oil-additive blends come from the same factories.
I run a synthetic from a scandinavian automotive warehouse chain called "biltema" and at one point, I know they got their oil frm the same refinery as some considerably more expensive brands.
I allso managed to obtain the data for this oil, and it turned out to be quite good!
Best thing is that it costs less than many mineral oils from the more "known" brands, so the economic penalty from frequent changes is insignificant.
So what intervals to change at?
I change at least two times a year, irrespective of mileage. I allways try to change oil at the end of the season before I put the car away for the winter so as not to leave oil with misture and corrosive breakdown and combustion by-products standing in the engine. Then sometime mid season.
what with mileage?
This will depend on the condition of the engine, how it's driven etc.
Short trips means the oil doesn't allways heat up enough for condensation and fuel residues to evaporate. Fuel residues dillute the oil reducing oil pressure and load bearing capacity. If then driven for a longer trip, the oil level can allso drop unexpectedly due to fuel evaporating back out of the oil.
Water causes faming (mayonaise) and corrosion. Not good.
higher mileage and / or harder driving simply means the oil gets worn out quicker.
A good working oil pressure gauge is usefull. After an oil change you will at some point see that oil pressure will decrease over time. this is the viscosity of the oil being changed. you may allso se the rate of change differ between brands of oil, especially synthetic vs mineral. This is to some extendt a subjective judgement call, but nevertheless a good indicator for whats going on in YOUR engine with YOUR oil.
Smell and feel and look at the oil. All engine oil gets blackened by soot particles fairly quickly. but there are ranges from very dark brown which is still translucent against the metal of the dipstick, to something which is pitch black and totally non translucnet, even if smeared out thinnly on the dipstic. you don't want the oil to have the appearance of tar or black paint.
This is again quite subjective, but pay atention to how the appearance developes from an oil change an onwards.
Smell.
Distinct petrol odor is bad, likewise a very burned smell. Use the smell of fresh oil as a reference, and when you don't reckognise the smell any more, you might consider an oil change.
even when dark and "sooty" used oil should feel like new oil when you rub it between your fingertips.thios can be rather subtle, but a distinguishable difference means you are probably overdue.
Rather than being an absolute or specific recommendation, I hope this can be of some general interrest and help form a basis for people to make some informed considerations and decisions.
When I "inherited" my fathers '88 model Toyota, I removed the cylinder head to fix a burned exhaust valve seat.
There were no coke or gum deposits. The hone marks in the cylinders were like new.
At that time, the car had done over 310 000 miles.
My father ran frequent filter and oil changes with Mobil 1 and used an engine heater during winter. I continued that routine for the four years I had it, only using the less expensive warehouse synthetic.
I can't say how that engine would have been another oil/ maintencance regime, but it did apparently work, and quite well too.
One thing is for sure, when it comes to lubricants, there is a lot of unfounded subjectivity, marketing hype and snake-oil out there!
and if you take specific advice from somebody, do so from people who have consistent experience over time and have seen evidence, good or bad, by looking at actual engine internals.
