The Advantages of Synthetic Oils over Mineral oils

oilman

Junior Member
Messages
181
The Advantages of Synthetic Oils over Mineral oils

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
Surface-active meaning a thin layer of oil on the surfaces at all times (in ester based oils)


How Synthetic oils Achieve these Benefits

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 it's 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.

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, rather than being modified from something that came
out of the ground to be as good as they can for a purpose.

Cheers

Tim
 

BennyD

Sea Urchin Pate
Messages
15,006
Thanks Tim, very interesting and informative. However, a major drawback of synthetic oils is that they don't smell as good as minerals when burnt by a two stroke engine, or leave the same amount of blue haze behind when gassing it.
 

Emtee

New Member
Messages
8,446
Thanks Tim, very interesting and informative. However, a major drawback of synthetic oils is that they don't smell as good as minerals when burnt by a two stroke engine, or leave the same amount of blue haze behind when gassing it.

haha, and it also depends what car you're talking about. I wouldn't put a fully synthetic anywhere near my Exxy.
 

alfatwo

Member
Messages
5,517
Yea,I definatly wouldn't put fully synthetic oil anywhere near a 1960s/70s Alfa,you'd be asking for trouble!
 

Phil the Brit

Member
Messages
1,499
I have a question for the more knowledgeable people........If a car only does say 1000 miles a year and service interval oil change is say every 10,000 miles why should the synthetic oil not be left in the engine for 10 years? Synthetic oil doesn't go off does it?
 

oilman

Junior Member
Messages
181
Thanks Tim, very interesting and informative. However, a major drawback of synthetic oils is that they don't smell as good as minerals when burnt by a two stroke engine, or leave the same amount of blue haze behind when gassing it.

Hi

That would be the castor based oils rather than mineral ones. There are castor and synthetic blended 2 strokes.

Cheers

Tim
 

oilman

Junior Member
Messages
181
Yea,I definatly wouldn't put fully synthetic oil anywhere near a 1960s/70s Alfa,you'd be asking for trouble!

haha, and it also depends what car you're talking about. I wouldn't put a fully synthetic anywhere near my Exxy.

Hi

Why would that be? What would be the harm of using a synthetic in an older car that has been rebuilt, so the seals would be compatible with a synthetic? A friend of my boss has a few 1930s Austin 7s and uses top end synthetics in those. One completed and Lands End - John O'Groats - Lands End trip last year and another is used for classic racing.

Here's an article I did for a classic car magazine last year

We get a lot of questions about oils for classic cars and the owners are usually surprised to hear that we often recommend using a synthetic oil if they want the best protection for their pride and joy. Unfortunately, there are a lot of rumours about synthetic oils, especially in classic vehicles, and it puts people off using the best choice for their cars. Here are some of the things that we often hear.

“You just can't use synthetic oils in classic cars”

No. The word synthetic is not a very accurate description of an oil as there are different types of synthetic oil. The top level of synthetic oil is an ester based synthetic, followed by a PAO synthetic and then a hydrocracked oil. Ester based and PAO synthetics are proper lab-made synthetic oils, but hydrocracked oils are highly modified and refined mineral oils, so far away from what they were when they came out of the ground that they are legally sold as a synthetic, so a lot of synthetics are actually just very good mineral oils.

“Synthetic oils are too thin for classic cars”

No. You can make a synthetic oil thinner than a mineral oil, but if an oil is a certain grade, it is pretty much the same viscosity (oil grades are a band of viscosity rather than an exact point) whether it's a synthetic, semi-synthetic or mineral oil.

“Synthetic oils damage seals”

There are certain cars (mainly ones that have not been rebuilt since synthetic oils have been on the market) where the seals do not like synthetic oils and they can leak a little more. They are in the minority though, most seals are helped by synthetic oils as they contain agents that help to swell the seals and prevent leakage. When synthetic oils started appearing (mid 70s), seal manufacturers altered the seals that they used so that they were compatible with synthetic oils and if the car has been rebuilt since then, the seals will be fine with synthetic oil.

“Modern oils do not have enough zinc for classic engines”

Certain modern oils do have reduced zinc levels, but that is with the latest API SM and SN specifications and those oils are aimed at low emission cars – not the sort of thing you use in a classic. Modern ester based oils, which are usually sold as race oils (although absolutely fine for road use), tend to have a ZDDP (the form that the zinc is in) content of around 1400ppm. They also have the ester content that helps to give the best level of protection possible.

“You can't mix synthetic oils with mineral oils”

You can. Many people think that because their car has used a mineral oil for many years, you can't change to a full synthetic as there will be traces of mineral oil left in the engine. Mineral and synthetic oils mix without issue, the only problem is with castor or biodegradable oils. They don't mix with mineral or synthetic oils, so be careful if you want to change to or from one of those.


We deal with a few Austin 7s from the 1930s, not something that would normally use a synthetic oil, but one of them recently completed a Lands End to John O'Groats and back again trip using an ester based 20w-50 synthetic oil, the Fuchs Pro R 20w-50. When we went to the Classic Le Mans series at Silverstone a couple of years ago, we found that the majority of the cars there were using Motul 300V, another top end synthetic oil. Admittedly, those oils are not cheap, but if you want the best for your car, they are very good options.

Ester based oils have a few advantages that make them the best choice.
1. They cling to the inside of the engine, so when the car starts up, there is already oil in place. That is a big bonus if the car is not used for a while.
2. The ester content makes the oil a better all round lubricant than other oils.
3. They are more stable at higher temperatures, making them ideal for performance use.

If your budget doesn't stretch to an ester based synthetic, there are still plenty of good mineral based oils to pick from, but to an extent, you get what you pay for with oil. One 20w-50 is not the same as the next one, just because they are both mineral oils.

We do advise caution when using synthetic oils in engines that have not been rebuilt as there can be problems with seals and dislodging deposits that have built up in the engine over time. Also, they are not compatible with gauze filters. If you have any queries, please contact us.


Cheers

Tim
 

oilman

Junior Member
Messages
181
I have a question for the more knowledgeable people........If a car only does say 1000 miles a year and service interval oil change is say every 10,000 miles why should the synthetic oil not be left in the engine for 10 years? Synthetic oil doesn't go off does it?

Hi

The problem with that would be the additive package in the oil and strangely enough, the lack of use.

Once an oil has been opened, the additives used in it will start to oxidise and they are very important

http://www.opieoils.co.uk/pdfs/tech-articles/Oil-Additive-Package.pdf

Most oils are fine for a couple of years after they are opened.

If the 1000 miles are mainly short trips, which is what I'd expect with that kind of mileage, any fuel and moisture that enters the oil is unlikely to burn off and that will also cause the oil to degrade.

Cheers

Tim
 

Emtee

New Member
Messages
8,446
Hi Tim,

No of course you are right, but until I re-build my engine I'm quite happy for all the crud that I know is in my 30 year old engine to stay in all those dark corners where the less efficient, old fashioned semi-synthetic oil can't get at it. It's out of harms way, just as I like it for the time being. Sticking a fully synthetic in there would be like giving my old decrepit car a colonic irrigation. The results, like an oil flush, would not be pretty.

When I do re-build, then I'll be taking your advice and starting as I mean to go on with a FS.

Regards, Miles.
 

Brendan

Member
Messages
1,221
Hi

The problem with that would be the additive package in the oil and strangely enough, the lack of use.

Once an oil has been opened, the additives used in it will start to oxidise and they are very important

http://www.opieoils.co.uk/pdfs/tech-articles/Oil-Additive-Package.pdf

Most oils are fine for a couple of years after they are opened.

If the 1000 miles are mainly short trips, which is what I'd expect with that kind of mileage, any fuel and moisture that enters the oil is unlikely to burn off and that will also cause the oil to degrade.

Cheers

Tim

So are you saying cars that do less than say 5k pa should have their oil changed annually? I see a lot of cars manufacturers recommend every 2 years
 

oilman

Junior Member
Messages
181
Hi

Ideally, yes the oil should be changed annually. I have come across a fair few threads on forums where cars that are on a 2 year/20k schedule as standard were suffering with sludge issues by the time they were 5 or 6 years old. There seemed to be two contributing factors, 1) Servicing the car every 2 years, but only covering 8-12k in that time, or 2) Using oil that claims to be suitable for long life servicing, but is not approved. Some of those cars had been serviced by dealerships, so can only assume they have used proper approved oils, therefore the mileage seems to have caused the issue, in other cases they have bought an oil that says 'Meets the requirements of' or 'Suitable for', but did not specifically say 'Approved by', so in those cases you are taking the oil manufacturers word that their oils meet the required specifications for long life servicing. Cars that were covering 20k in 2 years or less tended not to have the same issues, as long as the correct oils were used.

One thing to consider is that the manufacturers recommend oil changes every two years. It makes the servicing package look cheaper than cars on an annual service schedule, but also (this might just be my view of car makers) why would they want a car to last a long time? Okay, if a (mainstream) car doesn't make 100k or 10 years, then it's pretty bad and affects their reputation, but after that point the manufacturers want the customers to have to buy parts or a new car eventually.

Cheers

Tim
 
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