na užuojauta tiem, katrie iki 2000 rpm važinėja, ar bijo virš 4000 pakelt, ale variklį sugadins...
ir dar citata nuo brumburum:
Tai kaip tik 10W** geriau nei 5W** vasara, nes nuo karscio tepalai skysteja (klampumas mazeja)... Va su 5W** gali tureti vasara problemu, nes suskisteja stipriai... per visus senus salnikus gali pradet varyt...
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supraskit, kad W tai neturi jokios įtakos darbinės temp (80-100) laipsnių alyvai, W tik nurodo ant kiek `kieta` alyva bus prie šalto paleidimo, juk ar ten 0w ar 10w, jin bus DAUG kietesnė nei prie 100C SAE40 alyva. nepamenu ar ten prie 40 ar kiek laipsnių testuojama, bet tai pagalvok, jei 0w40 naudosi vietoj 10w40, kaip jin gali būt per skysta, jei 0w reiškia, kad esant šaltam paleidimui jin nebus tiek sustingus kaip 10w?
juk 0w nereiškia, kad ten vanduo. juk prie 100C alyva bus daaaug skystesnė, ir tas W nieko nebereikš, nes W tiesiog nebeatliks savo darbo, na taip pagaminta alyva, kad W skysta prie žemos temp, o kitos medžiagos prie aukštos temp.
p.s. o kas dėl SAE60 alyvos, tai jin tiesiog bus per tiršta prie 100c, jin naudinga, jei tai ypač karštas klimatas arba variklis dirba didelėm apsukom, ko pasekoje pasiekiama ~120c ar pan, tada jis suskystėja panašiai kaip SAE40 alyva. ta prasme SAE40 tokiom sąlygom taptu per skysta, dėl ko ir yra SAE50/60 pasirinkimas
bet kasdiena į darbą ant 2000 rpm naudot SAE60 tai čia jau toli nuo normos.
na ir dar biški ištraukų iš sukauptos medžiagos, gal kam įdomu... :
ALL oils labelled 40 must fall within the SAE parameters at 100degC so everything from a monograde 40 to multigrade 0w-40, 5w-40, 10w-40, 15w-40 are the same thickness at 100degC.
Common misconception about 0w and 5w oils being too thin
I read on many forums about 0w and 5w oils being too thin. I will try to explain it without getting over technical and we'll go from there.
0w-40, 5w-40, 10w-40 and 15w-40 are all the same thickness (14cst) at 100degC.
Centistokes (cst) is the measure of a fluid's resistance to flow (viscosity). It is calculated in terms of the time required for a standard quantity of fluid at a certain temperature to flow through a standard orifice. The higher the value, the more viscous the fluid. As viscosity varies with temperature, the value is meaningless unless accompanied by the temperature at which it is measured. In the case of oils, viscosity is generally reported in
centistokes (cst) and usually measured at 40degC and 100degC.
So, all oils that end in 40 (sae 40) are around 14cst thickness at 100degC.
This applies to all oils that end in the same number, all oils that end in 50 (sae 50) are around 18.5cst at 100degC and all oils that end in 60 (sae 60) are around 24cst at 100degC.
Now, ALL oils are thicker when cold. Confused? It's true and here is a table to illustrate this.
SAE 40 (straight 40)
Temp degC.........................Viscosity (thickness)
0..........................................2579cst
20..........................................473cst
40..........................................135cst
60..........................................52.2cs t
100........................................ 14cst
120.........................................8.8cst
As you will see, there is penty of viscosity at 0degC, in fact many times more than at 100degC and this is the problem especially in cold weather, can the oil flow quick enough to protect vital engine parts at start up. Not really!
So, given that an sae 40 is 14cst at 100degC which is adequate viscosity to protect the engine, and much thicker when cold, how can a 0w oil be too thin?
Well, it can't is the truth.
