engine oil grade differances

[steveo3002]

www.shell.com/global/products-services/on-the-road/oils-lubricants/right-oil.html

looking at the above link would it be fine to use 5/40 instead of 10/40

if I'm reading it right the 5w is to say how thick it will when its cold out ?

so a 5 would remain nice and a 20 would be like treacle ?

[Vintage75]

Yeah you are reading that correctly,
Only thing I would say is most older engines don't like modern thin oils or synthetic

[steveo3002]

yeah okay

but lets say if it liked 10/40 then 5/40 wont be any differant ? still 40 grade at temp?

[Vintage75]

There is very little difference between the 2 but you might find that you end up with noisy tappets on cold start up as the thinner oil will drain faster when the engine is switched off,
Why do you want to go for 5-40 instead of 10-40 ? I don't see much if any benefit !

[steveo3002]

been offered a great deal on several cans thats all

wont it be within 40 grade specs when i turn off ? then faster circualtion when cold

[Vintage75]

I'd go for it if you've got a great deal on offer, it's not going to do any damage.
What I meant was the oil will continue to drain for longer/faster as it's thinner when cold

[Vintage75]

^^
As long as it's good quality!
Possibly more important than grade. 

[welshpug]

depends a lot on the engine really, what is it?

[bortaf]

As said it really depends on the engine age and condition, i've used origional spec 10W50 oil in a pinto before and burned most of it off on the way to the rolling road, changed it in the car park for thicker 20/50 and no more smoke or problems, decent quality is more important than grade unless it's a tough old bird (like a Xflow or pinto) which as long as it's thibk enough not to burn off will run on any old oil