Whats Your Choice Of Oil For The $$

[Galois]

in what situation would you use 5-40 over 10-40?

rb25det

Doesn't matter much. They're very similar, and let's face it companies are more likely to round off to a factor of 5 rather than naming products 3w, 4w, 5w, 6w, 7w etc. So they might be very close.

Also since the w40 is common the viscosities of the two oils are constantly approaching eachother as they warm up.

Technically, if you're in a colder area the 5w might make it better for cold starts, but the difference will likely be negligible compared to the different quality 10w40's you find (eg: magnatec vs sougi).

[Galois]

On that SC article, it is a very interesting experiment but grossly oversimplifies an engine. Firstly, it is poor to compare oils of different viscosity because the thinner oils should have different film breaking characteristics to thicker oils (of almost identical composition) which would influence their result. Further, your car is not a spinning piece of metal grinding a bearing, it's a complicated closed system requiring oil transport.

The oil needs to be thick enough for protection and thin enough for drainage past the cylinders into the sump and adequately lubricate ALL parts of the engine+turbo. Interestingly viscosity is quite different to surface tension, which is what was on test here (trying to make the film break). The way the oil was cracked in processing, the additives used, the means of synthetic manufacture and the particular molecules used in production all change the surface tension the oil has.

The idea of testing oils is interesting and difficult. An engine oil may be perfect in every way except drainage and hence is useless. The results from the SC test are very interesting, but without knowing the particular chemical make up of the oils and allowing massive variables like viscosity, the results are pretty useless. And since the test has barely anything to do with an engine, it's even less useful for oil choice.

Edited October 8, 2010 by Galois

[sydking]

were should the oil pressure gauge be siting on start up and then when warm, since ive changed my oil it been different, sits between 0 and 4, sometimes at 4.

Any info appreciated.

[Tweaky]

wow i just found this on the internet... very interesting!! tell me what you think!

http://www.animegame.com/cars/Oil%20Tests.pdf

Very interesting topic on all the major brands of oils , especially some big names which aren't as really good as they claim to be ! I use Penrite Sin 5 in my skyline , never had any problems & shows it is one of the top quality performing oils on the market. Test results now prove it . Good job Penrite

[Paul SM]

Very interesting topic on all the major brands of oils , especially some big names which aren't as really good as they claim to be ! I use Penrite Sin 5 in my skyline , never had any problems & shows it is one of the top quality performing oils on the market. Test results now prove it . Good job Penrite

This test in SC mag was published back in March 2006 and has been the subject of intense discussion in SAU threads (just look through some of the recent posts.) SC mag did a follow up article after protests and criticisms by the companies whose oils didn't rate so well - I gather the main complaint was that the test wasn't comprehensive enough to provide a valid comparison of the overall qualities of each oil tested, although they did point out the limitations of the test in their intro.

If you accept that loading up a solid roller bearing onto a spinning metal wheel in an oil bath can represent wear between the moving parts of an engine, then you may be inclinded to draw the implied conclusions when choosing your oil. I have to admit that it seemed a good enough reason for me to change to Penrite Sin 5w-60 or Sin 0w-50.

[Wacky Dee]

were should the oil pressure gauge be siting on start up and then when warm, since ive changed my oil it been different, sits between 0 and 4, sometimes at 4.

Any info appreciated.

depends on the oil viscosity and how warm the engine is (or how cold it is outside on cold startup)

eg. I think normal is around 2 when completely warmed up. Also on cold startup, if it's a cold morning it should be between 5-7 (higher is better as the oil is thick when cold) Having said that, the stock oil pressure gauges are notorious for playing up... I had mine take a dive to 1 or so for a while but has since fixed itself.

[Paul SM]

All SC tests prove is, if I ever run out of grease, I can turn to a bottle of royal purple to grease up my garage door.

No suggestions for an alternative test, then...