the thicker it is it also takes longer to cycle through your engine, full synthetic, is the lighest and thinnest oil (for lack of a better word lol) so it reachs and goes through your engine alot quicker on startups then conventional oil too

Mobil 1 5w-30 here smile.gif

 

Based on ZIC oil, that is used on most Asian cars as OEM oil:

5W/30, 10W/30, 10W/40 - are semisynthetic.
5W/40, 5W/50 - fullysynthetic.


Again based on ZIC oil:

..SAE.............kinetic viscosity (-40C)............kinetic viscosity (100C)..............temp, when oil stops flow
5W/30.......................65.54.................... .................10.75........
............................... -45C
10W/30.....................76.71...................... ...............11.75..........
............................. -42.5
10W/40.....................101.9...................... ...............15.02..........
............................. -42.5
5W/40.......................84.17.................... .................13.75........
............................... -42.5
5W/50.......................116.0.................... .................18.12 ...................................... -47.5


So probably the best oil for winter is 5W/30, cause -40C viscosity is the lowest

But what oil is better for summer? With very low viscosity there may be no oil film between moving parts. Don't forget there are also oil for high performance cars (Castrol RS - 0W40 and 10W60)

 

<div class='quotetop'>QUOTE (Dmitry @ Feb 7 2006, 08:32 PM) <{POST_SNAPBACK}></div><div class='quotemain'>I think Hyundai just says what viscosity to use.

Notice, there are different oil classes, like SF, SG, SH, SL (for gasolin engines). SL now is the best. Mobil1, Castrol are SL (for example)

I think Hyundai says - SG or better.

why do you all use 5W-30, 0W-30 and not XX-W40?</div>

Actually SM is the best.

I use 10w30 Conventional all year long. I live in Michigan too.

 

i use mobil 1 synthetic 10w30 in mine all year long. great oil.

a buddy of mine uses amsoil 10w30 in his eclipse.