Oils 10w or 15w?

[Essential]

Just a quick question..

I normally run Motul 10w/30w in my rb20det .. as my cars done 120,000 ive decided to run a 10w rather then a 5w due for a little bit more added protection.

However today i stopped into super cheap to get some 'cheap oil' to flush out my engine and the guy rekons i have to run 15w/40w due to 10w/30w is too light for australian conditions

so which is the correct answer?

[Busky2k]

The higher the W (winter) rating doesnt mean better protection. The lower the number, the better cold start fluidity which is actually good Ie 0W40 provide better cold protection than an equivalent 15W40.

I'd probably get a 10W/40 (or any 0/5/10W 40) for your car considering its done a few miles and also our summers are damn hot, and moreover because I would assume your car is modified! Something like Shell Helix Ultra 5W40 or Motul Turbolight 10W40.

[Essential]

Yeah i run turbo light, I may have another look to see if theres a 10w/40 in the motul range.

I was under the impression the 10w was the weight the oil is when the egine is cold,and the 30 is the weight when the engine is hot, there for the highter the number the thicker the oil the thicker the engine protection

the lower the number the thinner the oil the lesser the engine protection however its lighter which is better performance

does that sound correct?

And for the record, im currently not modified

[Busky2k]

Yup your understanding is half correct. You want oil to be as thin as possible when cold so it circulates quickly to areas where oil is needed. An oil at 20C is on average 10x thicker than it is at 100C. So an oil doesnt 'thicken up' as the temp rises. Its just a number which is relative to the viscosity of a 'straight weight oil' compared to a multiweight like a 10W40. More info here;

http://www.vtr.org/maintain/oil-overview.html

You do a get a minute increase in performance using a 30 instead of a 40 weight oil. BUt its in the order of 0.5 - 1% which is almost nil. I'd stick with a 40 weight. 50 is abit too thick and in some cases, cause more wear in very cold climates.

[Essential]

Ok I read that website, Alot went straight over my head..

So I'm back at square one.

[Kinks]

0W has always seemed too light for my liking.. and given things really don't get that cold here I'd stick with at least a 5W. Oil pressure is important too, not just flow. The other rating is the hot viscosity which is more important (since, if you boost your car when it's cold you're an idiot). 40 for city use and 60 for track use is what I go by... I use motul 8100 which is 5W-40.

[Busky2k]

A 0W isnt too light at all. Its still 3-5x thicker at room temp than a 50 weight is at 100C. You want the oil at room temp (ie startup) to be as thin as possible..

[Essential]

I run 10/30 i dont want to run less then 10 due to my engine being a bit old.

however ive been told 30 is too light or soemthing.

im just so confused. all i know is i live in QLD atm with sumemr coming up it gets supidly hot up here and i want the best oil to protect my engine.

I use motul oil and want to stick with it. but i dont think they make a 10/40