Ok, you boys have got me worried now I was just about to get my car back on the road after few weeks of upgrading but now shes parked up until I figure out what oil to put in. Im getting shot of the mobile 1 0w 40 like you suggested but should I put in mobile 1 10w 40 semi synthetic or 15 50 fully synthetic? im running decat 255 pump with the intent of adding a scot t polar performance chip in the next few weeks should I use 15 50 because of the increase in boost / heat?

 

You'll be okay on either.

If you drive hard and often, I'd be inclined to stick in 15W-50.

 

Just put Mobil 1 15w 50 in mine, bought in Halfords and I think the only one not on offer and sold in a 4 lt container, fully synth branded as "Motorsport Formula"

 

Whats your feelings on vw's quantum platium 5w40 it seems quite good on the tin and i can aquire it on the cheap (i work for vw)
forgot to ad : 95 wrx auto about 80'000miles

 

I use the car for fun so it sees a lot of full throttle. My local Halfords sells 5L mobile 1 15w 50 Motorsport Formula for £38 and 10w40 is on offer for £20 but 15w 50 sounds safer for my hard driving

 

An additional £18 spread over at least c.3000-6000miles (depending on how often you like to change) is hardly a sacrifice if it means you're protecting the engine more!

 

ive been using 10w 60 castrol for two years now in my forged engine running good power as well and its fine and 10-50 will be fine and if standard power then 10-40 is fine to i think jusdt stick to what you know

 

Right guys, dragging this topic out the depths of the dustbin lol

So,My question is, from data given on this topic.......

standard engine seems to favour 10/40 (slightly thick when cold cranking, not too thick or thin when hot)

modified cars seem to favour 15/50, heres my question, why does a modified car require thicker oil for cold cranking ? and am i right in thinking the thicker oil at high temp is to help aid the extra power to be cooled ? and as it is cooling more, wont go too thin like a /40 oil would ?

 

Great thread resurrection!

A modified car does not require a thicker oil for cold cranking, it uses the same as a non modified engine. However some modified engines do prefer a thicker oil when being used hard and this is down to a few factors such as temps, fuel dilution etc.

So an ideal world be say a 5w-50 instead of a 15w-50 and these are available, however the viscosity gap in a 5w-50 is very large and has to be propped up by viscosity index improvers and these get broken down (shearing). So, a 15w-50 under hard use is less prone to shearing down then a 5w-50.

For heat transfer, in theory a thinner oil is best as it can absorb and lose heat quicker than a thicker oil, it will also move around the oil cooling system faster.

Cheers

Guy