can somebody please explain to me what does each character in motor oil means?

5w30, 0w30 10w40 what are the differences

thanks

 

first number is the cold start weight, second number is warm operating temp weight.

so a 0W-40 is very thin at start up (0 weight) and thicker once warm (40 weight). by contrast, a 10W-30 is a thicker oil at startup (10 weight) but a medium oil at operating temps (30 weight).

a lot has to do with how manufactureres rate their oil. a 30 weight is not set in stone. for example, mobil 1 5W-30 is more like a 0W-20. it's so far on the thin side of the scale for a 5W-30, it borders the thick side of a 0W-20 scale. by contrast, german made castrol syntec 0W-30 borders a 0W-40 or 5W-40. it runs on the thicker side of the oil weight scale.

best thing you can do is research oils and ask questions before deciding on an oil for your motor. my best advice would be to stay FAR AWAY from mobil 1 30 weights (0W-30, 5W-30, 10W-30, etc...) they're too thin for an LS1 and responsible for much of their reputation for ticking and consuming oil.

 

No such thing as a liquid that would have a true higher viscosity at lower temp then when heated. That would defy the laws of physics. Remember the concept of viscosity is the resistance to flow and it's thickness. The nature of anything liquid is that as temperature increases viscosity decreases.

The 0w 5w or 10w is simply a viscosity rating when the temperature is below 30F, the 2nd part is a viscosity rating when at operating temperature range for an oil. 0w is NOT thinner than 30. It is an apples to oranges comparison of the ratings numbers. 0w is thinner than 5w as is 20 is thinner than 30. The w denotes temps below 30F for viscosity.

The ratings though is not without it's flaws. There is a certain criteria that an oil has to follow in order to achieve a particular rating. Take Mobil 1, its oil for 5w30 meets all the criteria that denotes that rating when subjected to tests designed to see if it remains having the majority of the characteristics of being that weight of oil. The problem is that at operating temps, many batches of that oil fail to remain a 30 weight in terms of viscosity. If anything, the viscosity falls to the level of a 20 weight. At a 20 weight viscosity rating it is thin enough to be sucked in to the PCV system easily. It's not to say that the rest of the oil that meets the 30 weight criteria have also failed as well. It still provides the level of protection and wear characteristics of a 30 weight oil, it's just problematic for the LS1 engine design.

A properly formulated oil should adhere to all the criteria that makes the rating and not falter in any area. This is why German Castrol Syntec 0w30 is fairly ideal for our engines. As a 0w it already outflows 5w oil at lower temperatures and as a 30 weight will offer the level of protection demanded by our specifications. The key part of this oil is how well it retains being classified as a 30 weight oil when at operating temperatures. It is high enough in the 30 weight category for viscosity rating that is much closer to 40 weight oil just as Mobil 1 is low enough in the 30 weight category for viscosity to be a 20 weight oil. Also note that the 20, 30, 40 and 50 weights will overlap in their rating ranges. This is to allow normal people to screw up which oil to put in their cars just as much as give leeway to the oil companies to have a high yield of product. If the standards were not lax and wide ranged and overlapped, a lot of products would FAIL the established standards due to the way variances change so much while refining oil that no one batch is exactly the same.

There are upsides and downsides to these oils though, in theory Mobil 1 would rob less power from an engine due to less energy required to overcome the viscosity of the oil. In real world application, the variances are negligable enough that other factors like air temperature and wind resistance and similar factors will play a much larger role in power than oil weight.

 

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