Little confused about oil meanings

[Blunet600]

Why dont most vehicle i.e car or bike run on 5w or 0w? surely this is better for the engine as when it starts cold the oil is suited to it? I cant seem to make sense of it.
Could someone enlighten me?
cheers.
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Honda - Power of Dreams - NSR 125R - Hornet 600

[The Artist]

So the engine always has oil that is runny enough at all possible temperatures. You don't want it to go to -5 one night and you oil is frozen.

[Blunet600]

Oh i see, 5w wouldnt freeze would it? would need something alot colder than -5...right....?
I have a honda civic 1.4, if i put 10w-40 magnatec in it that would be ok right? someone suggested 5w-40 silkolene to me the other day.
Im running 10w-30 in my bike.
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Honda - Power of Dreams - NSR 125R - Hornet 600

[Kickstart]

Hi

Reason for a multigrade oil is that it acts like a (say) 5 weight oil when cold and a 40 weight oil when hot. But a cold 5 weight oil is probably still thicker than a hot 40 weight oil.

Thinner oils get pumped round more quickly on startup. However the oil acts as a barrier between engine parts and you need a thicker oil when it warms up to compensate for the oil thinning.

While you could just use an oil with a wider viscosity range, that requires more additives which break down (the oil itself lasts far longer), and so you land up with a shorter lived oil (main reason synthetics are better is that they are less reliant on additives, hence wear out more slowly and can have longer oil change intervals).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[P.]

[The Artist]

https://www.slunnie.com/coppermine/albums/userpics/10001/normal_EngineOilViscosity.jpg

https://www.sertec.com.py/telergia/telergia/informaciones/serie_400/16.gif

It is a compromise. Say you are somewhere the temperature never drops below 10c then you could run on SAE30 or something and be fine and this would be better for the engine but not worth the risk which is why in the UK, 10w40 is recommended for most vehicles. The engines are also designed to take that weight of oil.

[Blunet600]

Just read this....and confused me a bit more.
https://www.howstuffworks.com/framed.htm?parent=question164.htm&url=https://www.repairfaq.org/filipg/AUTO/F_oil_facts.html
Go down to number 4. multi-viscosity
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Honda - Power of Dreams - NSR 125R - Hornet 600

[WildGoose]

Thats merely a little light reading

Try this:
https://motorcycleinfo.calsci.com/Oils1.html

Explains all about additives, and their breakdown, and the difference between synthetic and mineral based oils. Although don't take it all as gospel because he says a lot of speculative things that aren't backed up with evidence to support them.

It's all really quite dull stuff, unless you are into that kind of science. It entertains me, because I like reading the comments on multiple internet forums from so called experts, who are talking absolute rhubarb.

"Has to be castrol in /that/ bike" etc and other such wibble.

Go with the oil weight recommended by the manufacturer for your climate, not necessarily the brand. Then sack off the likes of Castrol and Mobil 1 and buy the cheap equivalent from someone like Comma, found at most motor factors, and change it regularly.

There is a fair bit of evidence to suggest that anything marketed as "motorcycle oil" is just preying on the ignorant, as an excuse to charge way over the odds. It works of course, because most people don't care to do a bit of research.

The fact remains that you will be rid of your well bike before your oil choice next to another will make any real difference.
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So in other words, he stopped you for being flagrantly in posession of a motorcycle in direct contravention of the Hippies, Darkies and People Whose Face I Don't Like The Look of (Police Powers) Act. 1976