Why 10w40?

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Sharpedge
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Why 10w40?

Post by Sharpedge » Mon Nov 06, 2017 12:18 pm

I know there are a thousand debates on the internet over what grade of oil to use but no one seems to give a direct answer. Why 10w40?

Ive ridden only sportbikes and nothing else so far. Ive always used 10w40 because thats what everyone else is doing.

Recently, a mechanic/friend of mine recommended 15w50 instead. He claims the higher viscosity will better protect my NC35's engine and all the other moving parts involved.

Is he correct?

Fyi i live in southeast asia where the average temperature is 30-40 degrees celcius in the day and it gets quite humid...

magg
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Re: Why 10w40?

Post by magg » Mon Nov 06, 2017 12:57 pm

The selection of oil viscosity includes the ambient temperature range. Generally, lighter grades in low temperature environments and heavier grades in high. Tables are provided by the vehicle manufacturer as to their preferred oil viscosity vs operating environment temperature.

In your high ambient temperatures a heavier oil would probably be appropriate but you should consult the manufacturers owners/service manual.

Sharpedge
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Re: Why 10w40?

Post by Sharpedge » Tue Nov 07, 2017 1:27 am

thanks! thats a good enough answer for me.

Neosophist
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Re: Why 10w40?

Post by Neosophist » Tue Nov 07, 2017 7:48 am

big can of worms there!

The engine runs much hotter than your average daytime temperatures so that doesnt have a lot of bearing on when the bike is up to temp, its water / air cooled to maintain the correct range. Colder ambient temperatures can thicken up the oil making it hard to start / cause engine damage due to lack of flow.

A higher viscosity oil will leave a thicker film on the engine which takes more pressure to wear out but if its too thick itll rob engine power being harder to be pumped around, worst case it could cause engine damage as some engines have such small clearances / bearings (those designed for light weight oil) then the thicker oil can not easily flow into tight clearnaces / bearings. Not so much an issue with the old VFR engine.

Viscocity changes with temperature too as well as manufacturer, there is a range of tolerance.. at the farthest ends a 10-50 might only be slightly more viscious than a 10-40 depending on manufacturer.

The quality of oil is equally important, or more so how often its changed. especailly in a motorcycle as they share the gearbox. Oils degrade overtime, mineral oil the fastest so if not changed often enough wont provide adequate protection.

I run Honda mineral oil 10/40 G1 in all my bikes, changed regularly (12 months or 2000 miles).. none of them are raced though just street use used all year in all temperatures, never had any issues, one of the biggest issues is not changing the oil often enough regardless of type.. fully synth will last longer than between changes than mineral.

Friend once had 20/50 in a fireblade and had terrible valve rattle when cold due to poor oil flow.
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Re: Why 10w40?

Post by NGneer » Tue Nov 07, 2017 10:44 pm

As well as an NC 30 owner I also have a couple of classic british bikes (1951 & 1956). The later of these I restored in Cyprus and the documentation stated SAE 30 or SAE 50, dependant on where you are. SAE stands for Society of Automotive Engineers, the group that determines standards in motor oils and the number that follows SAE is the weight, or viscosity, of the oil. Lower numbers represent thinner oils, and higher numbers are thicker oils.

Therfore in in Cyprus where the ambient temp was (F****g warm) I used SAE 50 in my 1956 350cc single, also known as straight 50. I have recently moved back to Northern Europe and as such will from now on use SAE 30, a thinner oil to accommodate the lower ambient temperature.

Multigrade oils have the properties which enable them, in simple terms, to act as both a (for e.g.10/40) SAE 10 oil when cold and a SAE40 when warm.

In simple terms, 10/40 is the answer ......unless you live at one of the poles....or the equator :peace:


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