SYNTHETIC MYTHS
Discussion
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
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
opieoilman said:
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.
I've inferred from the above that aircooled motors require thicker oils.
My 993tt came using the thicker Mobil 1 variant and I've continued to use that.
Why would an air cooled motor require thicker oil?
Marquis_Rex said:
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.
I've inferred from the above that aircooled motors require thicker oils.
My 993tt came using the thicker Mobil 1 variant and I've continued to use that.
Why would an air cooled motor require thicker oil?
They tend to run hotter so normally sae 50's are specified.
Cheers
Simon
opieoilman said:
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.
I've inferred from the above that aircooled motors require thicker oils.
My 993tt came using the thicker Mobil 1 variant and I've continued to use that.
Why would an air cooled motor require thicker oil?
They tend to run hotter so normally sae 50's are specified.
Cheers
Simon
The oil is the heat-sink instead of coolant.
Another great post opieoilman, goes right along with what I'm being taught at a technical college.
I'm having a Vortech centrifugal supercharger fitted to my 2005 Mustang. The fitter has suggested that Mobil 1 is too thin for the application and I have 16 litres of the stuff. He says it can leak past gaskets for this reason and suggested at least a 5w.
So...fact or fiction? What would you suggest? I think I'm right in saying that dino oil is probably better for the breaking-in period but it seems to me that Mobil 1 would actually be better for cooling purposes.
So...fact or fiction? What would you suggest? I think I'm right in saying that dino oil is probably better for the breaking-in period but it seems to me that Mobil 1 would actually be better for cooling purposes.
Definately Dino oil and take it easy for 1000 miles then switch to a 5w-40 fully synthetic race oil would be my suggestion.
I doubt that 0w will in fact leak as it's 40 times thicker at 0degC than at 100degC but it's a question of overkill and formulation.
A 5w-40 of the same quality as M1 0w-40 will be more stable because of the narrower viscosity gap due to less VI Improvers.
Cheers
Simon
I doubt that 0w will in fact leak as it's 40 times thicker at 0degC than at 100degC but it's a question of overkill and formulation.
A 5w-40 of the same quality as M1 0w-40 will be more stable because of the narrower viscosity gap due to less VI Improvers.
Cheers
Simon
opieoilman said:
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.
I've been advised many times that it isn't a good idea to use fully synth oil in my rotary-powered RX-7 as it dries the seals, and to use cheap mineral-based stuff instead. Exception to the rule?
No not really, I have used 5w-30 fully synthetic in my RX8 for the last 6 months with nothing but benefits!
Oil consumption down by 40%
MPG 10% better
More responsive when accelarating hard
Less deposits on the exhaust.
There is a thread about my findings and other guinea pigs that joined me for the test on the RX8 Owners Club.
Cheers
Simon
Oil consumption down by 40%
MPG 10% better
More responsive when accelarating hard
Less deposits on the exhaust.
There is a thread about my findings and other guinea pigs that joined me for the test on the RX8 Owners Club.
Cheers
Simon
opieoilman said:
Definately Dino oil and take it easy for 1000 miles then switch to a 5w-40 fully synthetic race oil would be my suggestion.
I doubt that 0w will in fact leak as it's 40 times thicker at 0degC than at 100degC but it's a question of overkill and formulation.
A 5w-40 of the same quality as M1 0w-40 will be more stable because of the narrower viscosity gap due to less VI Improvers.
Cheers
Simon
Any views on the 15w/50 Motorsport variant of Mobil 1 in the same application?
Mr OilMan,
Many modern transmission components - like gearboxes and diffs, come "sealed for life". What is "life" as far as the manufacturers are concerned, and given that I like to run cars up to sky-high mileages at what stage should I be disregarding the "sealed for life" stuff and changing the oil? Also, should I use a different oil on a diff that has done say 150000 miles to that specified by the manufacturer?
Many modern transmission components - like gearboxes and diffs, come "sealed for life". What is "life" as far as the manufacturers are concerned, and given that I like to run cars up to sky-high mileages at what stage should I be disregarding the "sealed for life" stuff and changing the oil? Also, should I use a different oil on a diff that has done say 150000 miles to that specified by the manufacturer?
Interesting thread, I've been thinking about buying a MkIII Supra (3.0 7MGTE engine) and so I've been looking around on some forums to find out about them.
Lots of people claim that synthetic oils are too thin for the engine and that mineral oils changed ludicrously often are the only way to go. Thanks for confirming that I'm not going bonkers and that a synthetic oil is just as thick as a mineral one of the same grade
Lots of people claim that synthetic oils are too thin for the engine and that mineral oils changed ludicrously often are the only way to go. Thanks for confirming that I'm not going bonkers and that a synthetic oil is just as thick as a mineral one of the same grade
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