oil thickness and coding???

[Jono FD3]

guys, I\'ve got a quick question, in the MR2 (my knock about) they recoment 10-40 semi synthetic (IIRC), but due to the age of the car & the mileage, it is using a little oil so I am considering putting in a thicker oil to reduce the consumption, any idea which way the oil grades work?
is 15-40 thicker or would it be 5-40??

Cheers
Jono

[G@NDY]

Jono, I think ( could be wrong however ) thats if its 10w 40 then its 10 whatevers when its warm so the higher the number the thicker the oil when warm. HTH matey.

[neil_jdmr]

As above i think the 10/40 goes like this, the 10 is the viscosity grade at 40 degrees
 
so 5/40 is thinner at 40 degrees and 15/40 is thicker at 40 degrees
 
Hence go for 15/40 as its thicker but tbh if your burning off 10/40 semi then something else is on the way out.

[J_T]

I had a quick search for this a while back and this page seemed to explain pretty well:

http://www.driverstechnology.co.uk/oil-technology.htm

[Jono FD3]

yea, the oil control rings are shot!, but thicker oil will mean less will pass

J