|
What difference would using 10w40 oil instead of 5w30 make to an engine.
|
This might help you:
tinyurl.com/bceh
|
|
|
It's thicker when cold 10w instead of 5w (poorer cold start protection) and thicker when hot sae 40 instead of 30 (will withstand higher operating temps).
This may be of help:
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
|
Great stuff.
Moderators - could that possibly be added to the 'oil spec' sticky please?
|
Moderators - could that possibly be added to the 'oil spec' sticky please?
Done. DD.
|
Brilliant. I'll cut that exposition and keep for future reference.
But I'd stick my neck out and say that even more important than the right viscosity is to change the oil regularly, as HJ recommends. I'd like to see a long-term comparison between a new engine with the correct oil but long change intervals, and the same engine with budget oil changed every 5000 miles.
|
|
|
|
GOOD QUESTION:
I am a petrol head and take real notice of oil. In y LPG cars I am pleased with the way the oil stays clean and honey coloured.
When I removed the damaged XUD9TE engine from a PUG 306 XTDT I bought cheap I noted the foulness of the oil.
Not to mention little of it which I think caused the engine to destroy itself.
SO first start on replacement engine was a flush 1000 km only and I used the following...
Gulf Western 20w-50 exceeeds API SG/CD suit Torbo diesel to GVM 6 tonnes.
In a word BLEAH.
Went dark really quickly and very thin.
Came out like water and lots of carbon.
Engine got rattly.
At 1500 K I am now running new filter and the following.
CAT DIESEL CH-4
15W-40
This is what we use in our EPP twin turbo cat V12.
I think it will suffice.
Smells nice.
Engine is quieter.
Time will tell.
Any comments?
|
|
|
