Can't really think of how to title it, but when you're doing an oil change in your car do you actually read the little chart thing in the manual where it tells you what oil is suitable for what temperature, or do you just go for the broadest range multigrade you can find?
Only realised today I can safely run mine on 15w40 even as low as -10 C (according to this chart).
All I normally do is bung in whatever fully synth 5w30/40 (30 for Ford, 40 for Pug) is cheapest at the time.
|
That's a good question - according to the chart in my MB's handbook, I could use pretty well anything in the UK.
I assumed the best combination would be as low as possible viscosity when cold (ie 0) and as high when hot (50). I've used both 5W30 and 0W40 with no noticeable difference.
|
|
A low W-rating helps with oil flow when starting in very cold weather. Hot viscosity specifications have been gradually reduced for reasons of improving fuel economy. I think people worry far too much about engine oil - it is extremely rare to see a lubrication problem unless its due to extreme neglect. Strangely, people see to neglect the lubriaction of their transmission (manual or auto) which can be just as expensive to put right. Transmission oil choice is far more critical.
|
|
|
|
|
Yes, but only once, as it turns out that as long as the oil has a VAG spec of VW500.00, I can have any multigrade I like. Slightly confused though, as without that spec, it mustn?t have a winter grade of less than 10w. What with it being an old engine/high mileage, I decide to opt for nothing less than a 10w winter grade anyway.
|
.. do you just go for the broadest range multigrade you can find? ..
missltw: the best i can do is quote this
" .... It is time to dispel the notion that 0W-30 oil is too thin when our manual calls for 10W-30. A 0W-30 is always the better choice, always. The 0W-30 is not thinner. It is the same thickness as the 10W-30 at operating temperatures. The difference is when you turn your engine off for the night. Both oils thicken over the evening and night. They both had a thickness, a viscosity of 10 when you got home and turned your engine off. That was the perfect thickness for engine operation.
As cooling occurs and you wake up ready to go back to work the next day the oils have gotten too thick for your engine to lubricate properly. It is 75 F outside this morning. One oil thickened to a viscosity of say 90. The other thickened to a viscosity of 40. Both are too thick in the morning at startup. But 40 is better than 90. Your engine wants the oil to have a thickness of 10 to work properly. You are better off starting with the viscosity of 40 than the honey - like oil with a viscosity of 90. ..... ....
more details from 63.240.161.99/motoroil/index.html
|
They both had a thickness, a viscosity of 10 when you got home and turned your engine off. That was the perfect thickness for engine operation.
Surely that 10 should be 30 ?
|
... Surely that 10 should be 30 ? ..
>>
ashok - answer below is from the page at the link given.
" .....
Please forget those numbers on the oil can. They really should be letters as AW-M, BW-N or CW-P. The fact that we are dealing with a system of numbers on the can makes people think that they represent the viscosity of the oil inside the can. The problem is that the viscosity of oil varies with its temperature. A ?30? weight oil has a viscosity of 3 at 302 F ( 150 C ) and thickens to 10 at 212 F ( 100 C ). It further thickens to a viscosity of 100 at 104 F ( 40 C ) and is too thick to measure at the freezing point of 32 F ( 0 C ).
30 weight oil:
Temperature ( F )....Thickness
302...........................3
212..........................10
104..........................100
32..........................250 (rough estimate)
The automotive designers usually call for their engines to run at 212 F oil and water temperature with an oil thickness of 10. This is the viscosity of the oil, not the weight as labeled on the oil can. I want to stay away from those numbers as they are confusing. We are talking about oil thickness, not oil can labeling. This will be discussed later. Forget the numbers on that oil can for now. We are only discussing the thickness of the oil that the engine requires during normal operating conditions.
The engine is designed to run at 212 F at all external temperatures from Alaska to Florida. You can get in your car in Florida in September and drive zig-zag to Alaska arriving in November. The best thing for your engine would be that it was never turned off, you simply kept driving day and night. The oil thickness would be uniform, it would always be 10. In a perfect world the oil thickness would be 10 at all times and all temperatures.
If the thickness of oil was 10 when you got in your car in the morning and 10 while driving it would be perfect. You would not have to warm up your engine. You could just get in the car and step on the gas. There would be little wear and tear on you engine, almost none. Unfortunately the world is not perfect.
The night before when you drove home from work the car was up the the correct operating temperature and the oil was the correct thickness, 10. Over night the engine cooled to room temperature and the oil thickened. It is 75 F in the morning now (I do live in Florida). The oil thickness is now around 150. It is too thick to lubricate an engine designed to run with an oil having a thickness of 10. ....
hope that helps.
|
:: edit ::
ashok - answer below is from the first page at the link given
63.240.161.99/motoroil/101.html
|
|
|
|
