Mineral vs Synthetic oil
 

Are synthetic oils any better than mineral oils?

I thought this would be of interest as It's probably the question I get asked the most.

Shame the answer isn't simple though!

The basic benefits are as follows:

Extended oil drain periods
Better wear protection and therefore extended engine life
Most synthetics give better MPG
They flow better when cold and are more thermally stable when hot
For synthetic oil containing esters - esters are "surface-active" meaning a thin layer of oil on the surfaces at all times

If you want to know the reasons why then please read on but, warning - Long Post!

Stable Basestocks

Synthetic oils are designed from pure, uniform synthetic basestocks, they contain no contaminants or unstable molecules which are prone to thermal and oxidative break down.

Because of their uniform molecular structure, synthetic lubricants operate with less internal and external friction than petroleum oils which have a non-uniform molecular structure.

The result is better heat control, and less heat means less stress to the lubricant.

Higher Percentage of Basestock

Synthetic oils contain a higher percentage of lubricant basestock than petroleum oils do.
This is because multi-viscosity oils need a great deal of pour point depressant and viscosity improvers to operate as a multigrade.
The basestocks actually do most of the lubricating. More basestocks mean a longer oil life.

Additives Used Up More Slowly

Petroleum basestocks are much more prone to oxidation than synthetic oils. Oxidation inhibitors are needed in greater quantities in petroleum oils as they are used up more quickly.

Synthetic oils do oxidize, but at a much slower rate therefore, oxidation inhibiting additives are used up more slowly.

Synthetic oils provide for better ring seal than petroleum oils do.

This minimizes blow-by and reduces contamination by combustion by-products. As a result, corrosion inhibiting additives have less work to do and will last much longer in a synthetic oil.

Excellent Heat Tolerance

Synthetics are simply more tolerant to extreme heat than petroleum oils are. When heat builds up within an engine, petroleum oils quickly begin to burn off. They are more volatile. The lighter molecules within petroleum oils turn to gas and what's left are the large molecules that are harder to pump.

Synthetics have far more resistance as they are more thermally stable to begin with and can take higher temperatures for longer periods without losing viscosity.

Heat Reduction

One of the major factors affecting engine life is component wear and/or failure, which is often the result of high temperature operation. The uniformly smooth molecular structure of synthetic oils gives them a much lower coefficient friction (they slip more easily over one another causing less friction) than petroleum oils.

Less friction means less heat and heat is a major contributor to engine component wear and failure, synthetic oils significantly reduce these two detrimental effects.

Since each molecule in a synthetic oil is of uniform size, each is equally likely to touch a component surface at any given time, thus moving a certain amount of heat into the oil stream and away from the component. This makes synthetic oils far superior heat transfer agents than conventional petroleum oils.

Greater Film Strength

Petroleum motor oils have very low film strength in comparison to synthetics. The film strength of a lubricant refers to its ability to maintain a film of lubricant between two objects when extreme pressure and heat are applied.
Synthetic oils will typically have a film strength of 5 to 10 times higher than petroleum oils of comparable viscosity.
Even though heavier weight oils typically have higher film strength than lighter weight oils, an sae 30 or 40 synthetic will typically have a higher film strength than an sae 50 or sae 60 petroleum oil.

A lighter grade synthetic can still maintain proper lubricity and reduce the chance of metal to metal contact. This means that you can use oils that provide far better fuel efficiency and cold weather protection without sacrificing engine protection under high temperature, high load conditions. Obviously, this is a big plus, because you can greatly reduce both cold temperature start-up wear and high temperature/high load engine wear using a low viscosity oil.

Engine Deposit Reduction

Petroleum oils tend to leave sludge, varnish and deposits behind after thermal and oxidative break down. They're better than they used to be, but it still occurs.

Deposit build-up leads to a significant reduction in engine performance and engine life as well as increasing the chance of costly repairs.

Synthetic oils have far superior thermal and oxidative stability and they leave engines virtually varnish, deposit and sludge-free.

Better Cold Temperature Fluidity

Synthetic oils do not contain the paraffins or other waxes which dramatically thicken petroleum oils during cold weather. As a result, they tend to flow much better during cold temperature starts and begin lubricating an engine almost immediately. This leads to significant engine wear reduction, and, therefore, longer engine life.

Improved Fuel Economy

Because of their uniform molecular structure, synthetic oils are tremendous friction reducers. Less friction leads to increased fuel economy and improved engine performance.

This means that more energy released from the combustion process can be transferred directly to the wheels due to the lower friction. Acceleration is more responsive and more powerful, using less fuel in the process.

In a petroleum oil, lighter molecules tend to boil off easily, leaving behind much heavier molecules which are difficult to pump. The engine loses more energy pumping these heavy molecules than if it were pumping lighter ones.

Since synthetic oils have more uniform molecules, fewer of these molecules tend to boil off and when they do, the molecules which are left are of the same size and pumpability is not affected.

In practice, the fuel economy benefits might be pretty marginal though!

Synthetics are better and in many ways, they are basically better by design as they are created by chemists in laboratories for a specific purpose.

Hope this helps!
- Guy

Interesting stuff oilman. Can you talk about semisynthetics too? That would be useful.
Ta!

Sure, what would you like to know about them?

Cheers

Guy

Would you go for fully synthetic rather than semi?

What are the pros and cons of semi synth, compared to fully synth?

Depends on what type of clutch you have- dry or wet -
My Dakar has a multi-disc oil-bath clutch, mechanically operated and I use Silkolene semi-synth whereas the R1200GS has a single plate dry clutch hydraulically operated- I use a Castrol fully synthetic in that.

It is the additives in some of the fully synthetic oils that can cause wet clutch bikes to slip. I do not know what type of clutch the Africa Twin has.

The more synth you have, the better it is, surely ? :)

I remember attending a seminar held by Shell about motor oils and from what I remember (it was a few years ago now), synthetic oils are pretty much better in every way than mineral oils. Obviously, apart from cost.

I always use semi-synth as for me its the best compromise between cost and efficiency.

Yes, I would go for synthetic over mineral, mainly becuase they are better, but not all synthetics are synthetic in the true sense of the word many are modified mineral oils sold as synthetic.

Cheers

Guy

Thanks - I didnt know that semi was classed as mineral.

Can you tell me this? - if I buy a cheaper m/cycle oil with the correct JASO/SAE codings, will it be as good as an oil twice the price?
In other words, is brand important? Can an oil be inferior if the codes are right?

Depends, yes mainly with oils you get what you payfor so an oil twice the price is likely to be better.

Also think of it this way, one oil may just be good enough to meet a JASO spec, another oil can also meet that spec but also exceed it by a long long way, but there is now spec to show this it will just show up as meet the same JASO spec.

Cheers

Guy

What are the differences, between mineral, semi-synthetic and fully synthetic oil?
 

Here's a bit more info on the topic from our friend John Rowland, the chief chemist at Silkolene....

"
Before we get into details, the first thing to realise that there is no chalk and cheese difference between mineral and synthetic based oils. After all, the chemical compounds which make mineral engine oils so much better are themselves synthetic. Synthetic lubricant bases are stepwise improvements on mineral oil, with more desirable properties and fewer undesirable ones.

The second important point is that there's no one thing called 'synthetic'!

There are several different types of synthetic lubricant, and to say something like: 'the Supergrunt XXR must have a full synthetic' is meaningless unless the 'expert' explains what sort of synthetic he means.

Equally, to imply that dreadful things will happen if the 1970 Hardley-Ableson Bluegrass is run on anything other than Pennsylvania mineral is ridiculous. It may not need a 2007 synthetic, but it isn't going to come to any harm if the owner uses a 2007 synthetic. The most basic type of synthetic is really a special mineral oil.

Known as 'hydrocracked' bases, these are made in oil refineries by putting certain types of mineral fraction through special processing, so they cost more than the usual mineral types but not much more. They are useful because they resist evaporation at high temperatures. Although used for years for genuine technical reasons, they are now popular with marketing men because the magic sexy word 'synthetic' can legitimately be printed on the label without spending much on the oil inside the can! Yes, all low-cost 'synthetics' contain anything from a few percent to 20 percent (i.e. 'semi-synthetic') of special mineral oil.

Using fairly simple chemical compounds or gases from oil refineries or other sources, it is possible to 'synthesise' or build up tailor-made lubricant molecules which have very desirable characteristics, such as great resistance to cold, heat, evaporation losses or excessive thinning as they get hot. These are the true synthetics, and the two that are used in engine oils are PAOs (poly alpha olefins) and esters. Neither is cheap!

PAOs are related to mineral oils, and are the ideal carriers for all the chemical compounds used in mineral oils. Because they do not gel at very low temperatures, all genuine 0W-something oils have to be based on PAOs to pass the 0W test at a sub-arctic -35C. Esters were originally made for jet engine lubricants, and to this day all jet oils are ester-based. Although similar in performance to PAOs, they have a valuable extra trick: they are good lubricants and help to protect metal surfaces.

As 0W- and 5W- grades are not usually recommended for motorcycles, perhaps the best all-round oil is a 10W/40 shear-stable semi-synthetic with some ester content.

Esters help with transmission and valve train lubrication. 100% fully-synthetic oils are actually quite rare, probably because they are very expensive to make, and even more expensive to buy.

Even so, an ester / PAO with a very shear stable multigrade polymer is the ultimate oil for high output engines that are worked hard, which means racing.
"

All good stuff

Cheers

In Europe, provided the price hasn't been pushed up by shipping an "average" oil 5000miles from the West coast of the USA, you do get what you pay for. The best motorcycle oils are made in the more developed European countries, but low price buys the cheap 'modified mineral' synthetic and not much of it, with a poor multigrade polymer. As is so often the case, quality does follow cost.

Thanks for posting all this very interesting info. I, for one, appreciate it.:thumbup1:

My Honda asks for a minimum SG quality oil. I found a 10/40 supermarket semisynthetic motorcycle oil which is rated SJ - which is above this minimum. This oil costs 4 euros (£3-ish) a litre. But I don't know if it contains the ideal additives mentioned by the Silkolene man. He suggests a semisynth, but of quality. How do I know it's quality? It seems the answer is cost.

I'd better start hunting for another oil? Do we get value for money from the big names, or are they cashing in on a name?

Problems problems!!!!

Well, with oil you get what you pay for and it's what's not in the oil that matters as addative packs vary in quality too. Many oils are made to a budget because in many applications it does not matter, afterall "any oil is better than no oil".

The problems tend to start with wet clutches and many cheaper oils (mainly car ones as opposed to proper bike ones) do not contain the correct additive pack and may contain friction modifiers which may cause slippage in the wet clutch.

If your bike has a wet clutch go for a bike oil that carries the correct JASO spec as it's designed for Japanese Motorbikes.

These are Japanese and International stanadards for Japanese bikes, I would personally always use a proper bike oil, more stable and contains the correct ingredients.

http://www.opieoils.co.uk/c-773-motorcycle-oils.aspx

A semi-synthetic for ordinary road use and a fully synthetic if modified, used hard or off the road.

Cheers
Simon

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