Motor Vehicle Engine Oil

moose4me, Apr 30, 5:25am
Can anyone tell me what the difference is in 15W 40 & 10W 30 - OIL - Thank You

msigg, Apr 30, 5:40am
10 - 15 not alot of difference, 10wWsupposed to be thinner for cold start up, hence circulate fractionally faster( which is when most of the wear in an engine is) 40W staying a bit thicker when hotter, Hard for me to explain, best to google and you will get the correct.

mugenb20b, Apr 30, 6:07am
That's actually spot on.

So, what you can do, is use 10w30 in autumn/winter and 15w40 in spring and summer.

tony9, Apr 30, 6:51am
The specification of the oil is more relevant in today's engines.

tweake, Apr 30, 7:58am
the W part is how thick it is when cold (measured at 0c), the other is how thick it is when hot (measured at 100c). the two ratings number are not similar eg 10w is not the same as 10 rating.
the catch is what is the running temp is your engine oil.

best thing is use oil pressure gauge and see what oil pressures your getting.
otherwise on a engine in good condition the manufacture typically has a chart of recommend oil ratings and temp ranges for that engine.

good idea in colder parts of the country to use different oils for summer and winter as mugenb20b has mentioned.

dublo, Apr 30, 8:50am
Don't forget the S/C ratings: S stands for Spark (petrol) Ignition, C for Compression (Diesel) ignition engines. Don't ask me what the chemical differences are but as a rough guide modern engines will commonly require SN/CF oils and pre-1990 engines will be happier with earlier grades such as SG/CC.
"Don't use modern-engine oil in old cars or old-engine oil in new ones."
Oil is the life-blood of the engine, don't get it wrong.

tweake, Feb 18, 5:41pm
yes, sort of.
the problem is they simply don't make the old engine oils anymore.
most have been superseded a long time ago.
generally speaking the new spec oils will work fine. however there is always some engines which do not play nicely with some oils.
for older engines i would stay away from the latest spec oils, especially anything designed for the latest emission standards.

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