|
Fri 22 Feb 2008 12:51
What does 10w-40 mean..? -
oilman
|
|
10w-40, what does it mean? We have answered thousands of oil questions in the last 4 years but the most frequently asked one is ?What do the numbers mean?? In short, if you see an expression such as 10W-40, the oil is a multigrade which simply means that the oil falls into 2 viscosity grades, in this case 10W and 40. This is made possible by the inclusion of a polymer, a component which slows down the rate of thinning as the oil warms up and slows down the rate of thickening as the oil cools down. Multigrades were first developed some 50 years ago to avoid the routine of using a thinner oil in winter and a thicker oil in summer. For a 10w-40 to attain the specification target a 10W (W = Winter please note!) the oil must have a certain maximum viscosity at low temperature. The actual viscosity and the temperature vary with the viscosity grade but in all cases the lower the number, the thinner the oil. For example a 5W oil is thinner than a 10W oil at temperatures encountered in UK winter conditions. This is important because a thinner oil will circulate faster on cold start, affording better engine protection and therefore lower long term wear! For a 10w-40 to attain the other specification target a ?40? oil must fall within certain limits at 100 degC. In this case the temperature target does not vary with the viscosity grade, if there is no "W" the measuring temperature is always 100degC. Again the lower the number the thinner the oil, a ?30? oil is thinner than a ?40? oil at 100 degC, which is typical of maximum bulk oil temperatures in an operating engine. Engine makers are, of course, very well aware of this and specify oils according to engine design features, oil pump capacities, manufacturing tolerances, ambient temperature conditions etc. It is important to follow these guidelines, they are important and are stipulated for good reasons. Finally, if the engine has been modified or is used in stressed conditions, the operating conditions may well be outside the original design envelope. The stress on the oil caused by increased maximum revs, power output and temperature may require that an oil of a different type and viscosity grade would be required. These examples show viscosities at different temperatures: Grade................0degC............10degC...... .........40degC...............100degC 0w-40...............665cst.............354cst........ ..........82cst................14cst 5w-40...............842cst............ 430cst..................91cst................14cst 10w-40.............874cst.............440cst .................91cst................14cst 15w-40...........1260cst.............595cst........... ......107cst................14cst In a nutshell, that?s what a multigrade is all about! Cheers Guy and the Opieoils.co.uk team Edited by Dynamic Dave on 22/02/2008 at 13:39 |
What does 10w-40 mean..?
Join the discussion
Related posts
Cars For Sale
Related News & Road Tests
-
Road Test:
Volvo S40 2003 Road Test
It’s not often I get to test a new car and it turns out to exceed all expectations. Okay, just about anything would have been better than the old Mitsubishi Carisma based Volvo S40. And the Mazda 3 had already given a foretaste of what to expect in the chassis department. If the new Volvo S40 had been just a little bit better than the Mazda 3 it would have been fine. -
Road Test:
Nissan X-Trail 2008 Road Test
I can’t tell you how reliable the new X-Trail is going to be. We won’t know about that for a year or two. -
Review:
Peugeot 1007 2005
.jpg)
Citroen C2 based, Verlizy designed city car with good safety credentials and a high spec. Easy front seat access to its tall cabin. -
Ask HJ:
Buying Bangernomics diesel
Due to my high mileage covering 27,000 miles in 18 months in my petrol Ford Focus, I'm now looking to buy a diesel to replace it. However, I've previously...