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Geeman
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Registered: 11-2003
Location: Grimsby
Posts: 2580
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Re: Oil Advice and Recommendations here
Do you have current prices for the Silkolene Pro S 10w-50 that you recommended for my track car?
Cheers...
Giles.
--- Giles.
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Oct/14/2004, 9:52 am
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oilman
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Registered: 07-2004
Posts: 92
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Re: Oil Advice and Recommendations here
Drop me an email sales@opieoils.co.uk
Cheers
Simon
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Oct/14/2004, 10:05 am
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oilman
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Registered: 07-2004
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Re: Oil Advice and Recommendations here
I was asked a question recently concerning viscosity and felt that my answer would benefit all here as well.
So, here it is.
What is this thing called viscosity?
It’s written on every can of oil and it’s the most important visible characteristic of an oil.
The viscosity of an oil tells you how it reacts in certain circumstances and how it performs as a lubricant.
When a oil is subjected to external forces, it resists flow due to internal molecular friction and viscosity is the measure of that internal friction. Viscosity is also commonly referred to as the measurement of the oils resistance to flow.
There are two methods of viewing an oils resistance to flow. Firstly there is Kinematic Viscosity which is expressed as units indicating the flow of volume over a period of time and this is measured in centistokes (cSt).
An oils viscosity can also be viewed by measured resistance. This is known as Apparent Viscosity and it is measured in centipoises (cP).
However in the real world an oils viscosity is also referred to in such terms as thin, light and low etc. This suggests that the oil flows or circulates more easily. Conversly, terms such as heavy and high etc suggest the fluid has a stronger resistance to flow.
The reason for viscosity being so important is because it is directly related to the oils load-carrying ability - The greater an oils viscosity, the greater the loads that it can withstand. (It must be added when new not over a period of time as all oils “shear down” with use)
An oil must be capable of separating the moving parts in your engine at the operating temperature. On the basis that an oils viscosity is related to its load carrying ability, you could be fooled into thinking that “thicker” oils are better at lubricating but, you’d be wrong in this assumption.
The fact is that in the wrong application a high viscosity oil can be just as damaging as using a low viscosity oil.
The use of an oil that’s too “thin” can cause metal-to-metal contact, poor sealing and increased oil consumption and conversely, an oil that’s too “thick” can cause increased friction, reduced energy efficiency, higher operating temperatures, and poor cold starts in cold temperatures.
It is very important that you select the correct oil, not too “light” or too “heavy” and your Owners Handbook is a very good place to start as it lists the temperatures and options.
Oils thicken at low temperatures and thin as the temperature increases. The actual rate of change is indicated by their viscosity index (this number normally listed on the oils technical data sheet indicates the degree of change in viscosity of an oil within a temperature range, currently 40-100 degrees centigrade)
An oil with a high viscosity index, will normally behave similarly at these two temperatures but an oil with a low viscosity index will behave quite differently. It will become very fluid, thin and pour easily at high temperatures. A higher index is better!
Multi-grade oils are designed to perform at high and low temperatures by adding polymers to a base oil (5w,10w, 15w etc) which are heat sensitive and “uncoil” to maintain the higher viscosity sae 30,40,50 etc. This means that the oil can be used “all year round” rather than using different oils for summer and winter.
It is important to understand that the selection of the correct oil for your car is not just guesswork, you must consider the temperatures at which you need the oil to operate a 0w, 5w oil is better for cold starts as the oil circulates more easily when it’s cold and is able to flow around the engine more easily and quickly, offering protection at the critical moments following cold engine start-up. These oils are also known to give better fuel economy and engine performance.
Finally, all oils “shear” or thin down with use and this means that an oil that started life as a 10w-40 will with use become a 10w-20. The period of time this takes depends on the type and quality of the oil.
The most “shear stable” oils are proper Synthetics, either PAO (Poly Alph Olefins) or Esters which have very high thermal stability. They are in general of the more expensive variety but last longer and give the best levels of protection.
Cheers
Simon
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Oct/20/2004, 10:28 am
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Geeman
E30 Zone Squatter
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Registered: 11-2003
Location: Grimsby
Posts: 2580
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Re: Oil Advice and Recommendations here
I actually understood that.
Thanks for that, very interesting. I never understood the rating before, but now it's pretty clear. 
--- Giles.
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Oct/20/2004, 11:08 am
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luxconvertible
E30 Zone Member
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Registered: 04-2004
Posts: 94
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Re: Oil Advice and Recommendations here
wots the best oil to use 4 a reno clio 16v i no it aint a bm but i'm tryin to help a mate out at work!! cheers i'm also running my 325 on castoril magnatex 10 40 any good?? cars done bout 160,000.  cheers
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Oct/20/2004, 6:15 pm
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oilman
E30 Zone Member
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Registered: 07-2004
Posts: 92
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Re: Oil Advice and Recommendations here
10w-40 or 5w-40 will be fine.
Cheers
Simon
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Oct/21/2004, 9:26 am
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e30t
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Registered: 10-2004
Posts: 196
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Re: Oil Advice and Recommendations here
whats the best oil for a 1988 325i
its done 261000 miles and i've just rebuilt the head?
--- 
i dont know where i'm going but
i'm definately making good time |
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Oct/22/2004, 6:12 pm
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oilman
E30 Zone Member
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Registered: 07-2004
Posts: 92
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Re: Oil Advice and Recommendations here
quote:
e30t wrote:
whats the best oil for a 1988 325i
its done 261000 miles and i've just rebuilt the head?
The stock recomendation for the car is a 10w-40 semi synthetic or a 5w-40 fully synthetic. Using a full synthetic will always provide better protection than a semi, but it is down to you as to whether you want to spend the money. Being a car of high mileage then a 10w-40 full synthetic would be better than the 5w-40.
If you want to go for a semi synthetic stick to a brand name as they tend to be of better quality, or e-mail me at sales@opieoils.co.uk and I will forward on to you some prices for good quality fully and semi synthetic oils.
Cheers
Guy.
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Oct/25/2004, 9:11 am
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Kilomph
E30 Zone Member
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Registered: 09-2004
Posts: 9
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Re: Oil Advice and Recommendations here
quote:
oilman wrote:
quote:
Dan325iSport wrote:
1989 325i Sport with 100k, has had head rebuild and it runs very well. It is used everyday.
I'm soon going to do a oil & filter change, in your opinion what is the best possible oil for it?
Cheers for your advice.
I would use 5w-40 fully synthetic for all year round use.
You can always email me for a price list.
Cheers
Simon
Mobil 1 only offers 5w30. What brand would you recommend instead? I have the same setup, 89 325iS with a little over 100k, and one head rebuild. Used as daily driver, and with winter coming temps won't get above 50 for the next 3-4 months. You recommend using 5w40 for the summer months too as well? It easily gets in the 90s during the summer months here in the US.
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Oct/26/2004, 1:15 am
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G G
E30 Zone Member
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Registered: 10-2004
Location: Glasgow
Posts: 39
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Re: Oil Advice and Recommendations here
Apparantly switching to a synthetic oil after using mineral oils for several years can be a bad thing.
Read the Oil Bible for yourself here:
http://www.chris-longhurst.com/carbibles/
sorry, dont know why this isnt a link, I put the code /code thing at either side
Last edited by G G, Oct/28/2004, 10:48 pm
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Oct/28/2004, 10:46 pm
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