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SYNTHETIC MYTHS

oilman

By oilman
in TechTalk

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oilman

oilman

Posted
Posted

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

 

 

Contact me:

sales@opieoils.co.uk

Oil data:

http://www.opieoils.co.uk/lubricants.htm

01209 215164

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old captain slow

old captain slow

Posted
Posted
Of minor and probably irrelevant interest. My son and I used to race a TKM 100 kart before he couldn't make the weight anymore. The engine generally needed a refresh after 6 hours running on mineral based 2-stroke oils as recommended by TKM that ususally involved new rings and piston as a minumum. On changing to (IIRC) Sylkolene fully synthetic 2-stroke oil it was still in good nick after 12 hours. Didn't take it any further than that but the engine looked like it would have gone further with no probs. The implication that the fully synthetic was streets ahead in terms of lubrication qualities on a relatively highly stressed engine.
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Graham Perry

Graham Perry

Posted
Posted

The synthetic oil that lasts forever (well the life of the vehicle) could be not that far away. BP was doing tests in Australia about 5 years ago on truck oils with super extended lifes of over 250,000 miles per drain. There was an interesting article in BP's in house Horizon magazine showing some 3 trailer roadtrains they were testing it on. I never heard what the result of this was or whether they ever had problems. The trucks had a very clever filtration device on it that while not reconstituting the oil did get rid of most of the nasties and it was able to detect when the oil got sufficiently out to spec that it needed changing.

 

 

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Brucey

Brucey

Posted
Posted

Mr Oilman,

 

I run my 1993 1400K ss on Comma semi synthetic. 100% road usage and change it every 5000 miles (well a bit before owing to the hole I put in the sump!)

 

I run my non turbo diesel 205 on semi synthetic (Comma diesel). Also changed every 5K (total 120K miles)

 

Apart from about £30, what's the difference between fully & semi synthetic?

In your opinion am I using the right stuff for my application and changing it at the right intervals?

 

Bruce.

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Roger King

Roger King

Posted
Posted

Speaking as one who used to build race engines rather than as an oil expert, I can vouch for the fact that engines raced on synthetic are always much cleaner in hot spots such as under the piston crown. I've also never seen sludge problems of any kind.

 

Purely as an experiment, I ran my Ka on Mobil 1 from 1000 miles and deliberately changed oil only every 25,000 miles. I'm not saying I'd recommend such lengthy intervals, but at 150,000 miles it still never needed topping up between changes.

 

One question - I, and some others have seen problems when running freshly built engines on synthetic from the word go, particularly failure to bed-in rings and cam lobe failures - it is of course possible that there were other causes, but any comments?

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eric

eric

Posted
Posted

Hello everybody and in particular to Mr Roger King

 

I had bought in 1998 a sprint crossflow engined seven

with an unknown mileage as it was a race car without speed counter

 

I put in it 10w40 Agip semi synthetic because I used it in my others car

 

I changed for Motul 300v 15w50 syntetic because of low pressure

at hot at idle (I live in Marseille and the summer is hot)

And it is now perfect and I have added 40.000 miles to unknown starting point and the engine seems to rev smoother with the Motul than the Agip I kept for 4 years

 

 

The new Motul is even better than the former one

 

All that to say that from my point of view , oil is very important even in old engines

 

eric

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Roger King

Roger King

Posted
Posted

From experience I and others have found that fully synthetic doesn't do the running in period any favours. This is purely an observation and I don't have any proven theories as to why.

 

My best informed guess is that the superior lubrication properties of synthetic hinder the bedding-in process of removing high spots by metal to metal contact (note that on an engine machined to modern standards this only occurs on a microscopic level). As to why we've also seen problems with new cam lobes failing, I'm puzzled - the only thing I know is that I've seen it more than once in engines run from new on synthetic (it could possibly just be a statistical blip).

 

Perhaps Oilman can answer these questions from a rather more informed postition.

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Normans_Ghost

Normans_Ghost

Posted
Posted

Roger, I have a friend that builds and flies his own aeroplanes. He is NOT allowed to fill a new engine with synthetic, only mineral until x hours flown.

 

Apparently they've had a lot of early engine failures on engines run in on synthetic.

 

I'll try and ring you tomorrow, we're off to France on 10/12.

 

Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here

You and your seven to The French Blatting Company Limited

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