Which synthetic oils are really synthetic?

[manga_blue]

Discovered this, which seems to explain why my Castrol Edge engine oil is going off so quickly.

http://www.technilube.com/sections/comps/synth_diff.htm

Is it right?

[manga_blue]

I changed to synthetic to see if I could extend oil changes to 10,000km, get oil to the lifters more quickly and just generally give better protection. Castrol Edge was the cheapest \"fully synthetic\" I found.

I know it's all subjective but ... after 4,000km the engine noise levels are returning to what they were, the time to quieten the lifters is getting pretty variable again and the oils looks and smells stale - just like any other 4,000km old dino oil.

[Brad]

I recently put Castrol Edge 10w60 in my car. I was running the semi-synth 5w30 and the oil pressure was dropping very low, under 1psi at idle in the heat. Sits almsot at 2 now.

That said, it has not fixed the HLA noise and sometime it even last longer, like yesterday when I was 200m up the road before it stopped. I feel better though that the pressure is up.

[Brad]

Brad - I hope you mean 1 - 2 kpa (14.5 - 29 psi)and not 1 psi.... you would have a real problem if you oil pressure was 1- 2 psi @ tickover or any other revs.
You really are using too thick on oil in your '5 - thats why you are getting HLA noises while the oil is still cool - its as thick as honey first thing in the morning, not good for engines..... Oil flow is far more important than pressure (in most circumstances) - thats why you dont use thick gear type oil in modern engines, more pressure = less flow.
Oil pressure @ tickover is your lowest priority as the engine is at its lowest stress level - its far more important to have good pressure at normal revs & engine temperature - 10 psi / 1000 rpm is the gold standard @ normal operating temps - any more and you are not getting enough flow.

Well, 1 on the guage, I thought it was actually in Bar. Running along at 60 around town on a hot day it used to sit at 2, now it sits at 4. On the track at full throttle and high revs it would only jsut get over 2. Not sure what it will do now but would have to be better.

What weight oil should I look for getting the oil lighter when cold and will give more pressure/flow when hot?

[manga_blue]

I used 0W40. The 0W meant it was thin enough cold to get up to the HLAs quickly (or at least it did while the oil was new). The 40 was allowing for the fact that the motor's done 150k km.
Any reading I've done said 0W40 or 5W30 were both OK, anything thicker than that was as Steve said about the 10W60 - you'd be struggling to pump it up when cold and you were risking not enough flow when hot.

[SuperMazdaKart]

interesting, will have to try out the 0-40 next time i change. only Castrol have a snyth oil in that range in Australia right? i don't think you can get Mobil 1 in 0-40 here? & Mobil one is so highly praised as the best generally even though it's a 5-50 or 10-30

[Okibi]

http://www.racq.com.au/cps/rde/xchg/racq_cms_production/hs.xsl/Motoring_Maint_Repairs_Foun_factsheet_engine_oil_designations_ENA_HTML.htm

API ratings listed.

http://www.api.org/certifications/engineoil/categories/upload/ShelfCard_English.pdf

[rodent]

Is there an idiot's guide to oils on the net somewhere that I can read up on? I still have no clue about what the numbers mean or how they translate into driving conditions

jonno.

[Okibi]

Currently ..

API SM - Best
API SL - Good
API SJ - Fine