Synthetic Myths

oilman

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I read so much stuff on the internet about Synthetic Oils that is simply not true so I felt it was time to tell the truth rather than accept the myth.

So in future when you see someone state any of these, please do me a favour and point them at this thread!

Synthetic motor oils damage seals:

Complete Nonsense! Any oil seals made after 1975 or thereabouts will be entirely compatible with any type of synthetic engine oil. (The same goes for synthetic gear oils and transmission oil seals.) It must be understood that everything associated with lubrication is thoroughly tested. The major oil manufacturers do not make oils that attack seals; seal manufacturers ensure that their products function correctly with modern lubricants.

Synthetic oils are too thin:

It is true that the best synthetic blends can be low viscosity (0w-20 for example), but they do not have to be! It is also true that the latest engines are designed to run on thin oil, which improves power output and fuel consumption. Even so, thicker synthetic based grades (10w-50, 15w-50, 20w-50etc) are available for air-cooled motors, older engines, or severe high temperature conditions. These grades can also benefit rebuilt classic engines dating back to the 1940s.

Synthetics mean higher oil usage:

The complete opposite of the truth. Oil consumption in well-maintained modern engines is mainly down to the oil evaporating at high temperatures. Synthetic base oils (specially the PAO and ester types) are very resistant to evaporation loss even in low viscosity blends, so oil consumption is minimised. Obviously, engines with worn valve guides, defective seals and worn piston rings will use oil regardless, so there is no point in using expensive synthetics as an ‘old banger lube’.

Synthetic oils are not compatible with other oils:

All engine oils intended for normal road use in recent 4-stroke engines are compatible with one another, regardless of the base make-up. (mineral, PAO/ester/hydrocracked synthetic, and semi-synthetic.) There is no need to flush or strip down an engine when changing from one type to another. (…but be careful with the exception: castor oil based racing oils.)

Synthetic oils produce sludge:

Well honestly, this is just totally daft. All synthetic bases are more resistant to oxidation than mineral oil, and sludge is largely due to oxidation. In any case, all motor oils intended for road use meet the higher API specs such as SH, SJ, SL and diesel equivalents. One of the main reasons for introducing the API specs back in the 1950s was to deal with oil sludge problems. All high-spec oils run very clean, especially synthetics.

Synthetic oils cannot be used with catalytic converters:

‘Cats’ will perform more efficiently and last longer if synthetic based engine oil is used. Their lower volatility (see 3 above) means that less oil reaches the combustion chambers via crankcase ventilation, so there are less harmful ash residues from burnt oil to de-activate the catalyst matrix.

Synthetic oils can void warranties:

People who make statements such as this never define the type of synthetic, thus revealing their ignorance. Provided that an oil meets or exceeds the API and viscosity ranges specified in the handbook, the warranty will not be affected. (By law, OEMs cannot insist that a particular brand of oil must be used to maintain warranty.)

Synthetic oils will last forever:

The better synthetic blends will certainly last longer*, especially in high performance or high annual mileage situations, but ‘forever’ is not on, simply because contaminants such as soot, and acid gasses from traces of sulphur in the fuel degrade the oil.
(*Provided that a very shear resistant VI improver polymer is used in the oil formulation to keep the viscosity up to spec. This point is often forgotten.

Synthetic oils are too expensive:

True, for older vehicles that use a lot of oil or are almost ready for the scrap yard. For cars that are worth maintaining, the right types of synthetic oil are a cost-effective way of retaining ‘as new’ performance, low fuel consumption, and reducing maintenance costs. (See 6 above, for example. ‘Cats’ aren’t cheap!)

Cheers
Simon
 

maddog

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How about synthetic oils knacker wet clutches;)?
 
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oilman

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I guess we're talking bike engines.

All proper synthetic bike oils have modifiers to prevent this happening, I guess it depends on the particular oil you are using.

Cheers
Simon
 

clive williams

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maddog said:
How about synthetic oils knacker wet clutches;)?
You can buy synthetic oil for wet clutches - another myth exploded!:D

Clive

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E320CDIT210
Aprilia RST 1000 with Motul Synthetic
 

dogsbody

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My daughter swiped some Magnetec from the garage to refill a Ford Fiesta, which her boyfriend had serviced. The oil consumption was truly horrendous, coupled with much smoke due to the oil passing through the valve stem oil seals, a known fault on CVH engines.
Moral of the story is that you must have the right oil for the job. Old and worn engines are often not suitable for synthetic oils, as the engineering tolerances are all wrong.
That said I have been using Synthetic for 10 years now without any problems, but it is important to choose the right oil relative to the engine.

One question for the forum is:
I have always been told to run a new engine on mineral oil to bed the rings down and to score slightly the bores, before changing the oil for synthetic at the 1500 mile service interval... which now seems not to exist!
What do other members do with a new engine?
 

maddog

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clive williams said:
You can buy synthetic oil for wet clutches - another myth exploded!:D

Clive

500E
E320CDIT210
Aprilia RST 1000 with Motul Synthetic

you can and others say they are fine for wet clutches but arent.

There are only a few synthetic oils i would use in a bike and I prefer to use mineral in real heavy duty applications
 

maddog

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dogsbody said:
My daughter swiped some Magnetec from the garage to refill a Ford Fiesta, which her boyfriend had serviced. The oil consumption was truly horrendous, coupled with much smoke due to the oil passing through the valve stem oil seals, a known fault on CVH engines.
Moral of the story is that you must have the right oil for the job. Old and worn engines are often not suitable for synthetic oils, as the engineering tolerances are all wrong.
That said I have been using Synthetic for 10 years now without any problems, but it is important to choose the right oil relative to the engine.

One question for the forum is:
I have always been told to run a new engine on mineral oil to bed the rings down and to score slightly the bores, before changing the oil for synthetic at the 1500 mile service interval... which now seems not to exist!
What do other members do with a new engine?

I dont think you should run an engine in with synthetic oils as its too slippery and takes longer for the parts to bed in. I prefer mineral oil for around 500-1000 miles and then complete oil and filter change and then run on fully synth if its a car or semi-synth if its a bike

I'm from the "treat it hard from new" school of running in and have found that works best for me but the only engines i play with nowadays are motorcycles and i tend to see the effects immediatly as i i rebuild them a few times a year.


The thing with synthetic oils and running in proceedures is you can find plently of evidence to support your case which ever side of the fence you sit
 

E280AUTO

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I have recentley had a 1938 six cylinder engine complete rebuild although not mercedes it has been filled with a running in oil. It will be some time before its reunited with the car, would a synthetic be suitable when in use. Im sure the garage reccomended this
 
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oilman

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E280AUTO said:
I have recentley had a 1938 six cylinder engine complete rebuild although not mercedes it has been filled with a running in oil. It will be some time before its reunited with the car, would a synthetic be suitable when in use. Im sure the garage reccomended this

One of the correct viscosity, finding it may be a problem. Engines of that age generally tended to run on monogrades.

Cheers
Simon
 

clive williams

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maddog said:
you can and others say they are fine for wet clutches but arent.

There are only a few synthetic oils i would use in a bike and I prefer to use mineral in real heavy duty applications

Perhaps I should have said that there are specific synthetic oils for wet (bike) clutches. However, I will always use synthetic oil for my cars and bike as the protection they give is superior to HD oils moreso in a modern, high revving, close tolerance, fine engineering bike engine even if there is a risk of a slipping clutch (which there isn't with specific bike oils).

Clive

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E320CDIT210
Aprilia RST 1000
 

maddog

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clive williams said:
Perhaps I should have said that there are specific synthetic oils for wet (bike) clutches.
Clive

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Aprilia RST 1000

No i was agreeing with you there are oils that claim to be fine for wet clutches but that isnt a guarantee.

The common offender for slipping clutches is felt to be an additive called molybdenum disulphide or moly.

I have no qualms about using synthetic oils in my cars or van
 

mercw126man

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Thanks for the thread; great background info.

Can I just suggest an excellent source (that many of your will already have heard of as they do octane enhancers etc), for all these oils including clutch friendly synthetic and awkward monogrades?

Millers Oils of Brighouse (01484 713201) or see www.millersoils.net. I've used them for years, they have a local shop and a network of stockists/buy online. Brilliant and very helpful.

Cheers!
 

maldon

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Way off thread, I've just filled the windscreen washer on the ML and checked the oil levels - fine but it is as black as your hat - the car has now covered8000 miles.

Will the oil have been changed with some form of first service? There is no service stamp in the service book only a sort of delivery check.
 

maddog

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maldon said:
Way off thread, I've just filled the windscreen washer on the ML and checked the oil levels - fine but it is as black as your hat - the car has now covered8000 miles.

Will the oil have been changed with some form of first service? There is no service stamp in the service book only a sort of delivery check.

probably not i dont recall there being a first service just take it in when the car tell you.

Oil on diesels does go black quickly anyhow
 


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