I had this reply from VW, yes all of you guys were correct, which I didn't doubt. I didn't understand the difference/benefits of using either grade.
Thank you for contacting Volkswagen Commercial Vehicles regarding the correct oil specification for the above vehicle.
I have liaised with our Technical Team who advise that we do not quote 0W-30/5W-30 generally, the oil has to meet VW 507 00 standard. This specification should be printed on the container of whatever brand of oil is your preferred choice.
Both 0W-30 and 5W-30 can be used, in order to help you make the right choice for your needs, I include some general information below:
Difference between 0W-30 and 5W-30
Motor oils come as Multigrade or Multi viscosity. They usually have two numbers in their label. You would normally find the numbers to be separated by a W; an example is 0W-30. The number or grading system was introduced by the Society of Automotive Engineers, SAE. The grading or number system helps to determine which oil grade is suitable for a particular temperature range.
The numbers are assigned to the oils based on the rate at which they flow at different temperatures, i.e., flow rate within a temperature range. The number could be 0,5,10, 20, 30…, 60. The number is a factor of the oil’s viscosity. The lower the grade or number, the thinner and less the viscosity of the oil.
The W in oil grade symbolizes Winter. A lower number which translates to less viscosity is much suitable for winter. 0W oil will flow up to a temperature of -30 degree Celsius while 5W will flow up to a temperature of -25 degree Celsius.
When Can Each Oil Be Used?
Determining the best scenario in which either 0W30 or 5W30 can be used depends on two factors. The first factor to be considered is Temperature while the second one is Viscosity. Most times, manufacturers will recommend the two oils ( 0W30 and 5W30) for you but choosing the best depends so much on the aforementioned factors. However, 0W30 can always be used in place of 0W50.
Concerning temperature, a quick one to always have in mind is that a standard engine needs oil that flows well under the current weather conditions. A 0W or 5W is a pointer to how easily each oil will flow in winter, ( W stands for winter). A 5W oil thickens more than a 0W ( 0W is thinner). So, in Winter, 0W-30 will be the most suitable oil to use.
Generally, in winter, when the temperature is much colder, the 0W-30 oil will work better and faster because it will easily warm up the moving parts and gliding surfaces of a car due to its lower viscosity. 5W-30 oil, on the other hand, is relatively thicker than the 0W-30 oil, and this makes it more suitable in a case of a relatively higher temperature.
So, for a cold weather, the 0W-30 motor oil is recommended while for the relatively warm weather, the 5W-30 motor oil is recommended.
Understanding Viscosity
Viscosity simply means opposition or resistance to flow. In much simpler terms, it can be referred to as the flowability of a substance.
When it comes to motor oils, the viscosity is denoted by the number before W. For example, in 5W-30, 5 is the viscosity number which is what determines the rate of flow of the oil at 0 degree Celsius. So, the lower the number, the lesser the viscosity and the lesser it thickens in the cold. With this, you will expect 0W-30 to thicken less in the cold than 5W-30.
A motor engine in a colder climate would get a lot of help from a 0W-30 motor oil than the 5W-30 motor oil. This is a factor of viscosity. The outside temperature also has a role to play in determining which viscosity is perfect for use. When the temperature is cold, the oil flows slowly, but when the temperature is hot, it will flow more quickly. For adequate and proper lubrication, you must always put the viscosity in relation to temperature into consideration.
Basically, motor oils are manufactured in different velocities to achieve effective lubrication in different climate conditions.
Fuel Economy
The kind of motor oil you choose can make a big difference on how much you save. The 0W-30 motor is renowned for its high capacity to improve fuel economy. The 5W-30 has a viscosity that is higher than the 0W-30, this can be clearly judged by the grade or number it carries. Oils are either thick or thin. Thick means the oil has a high viscosity while thin means the oil’s viscosity is low. It is same as the case of these two oils; the 5W-30 is thicker than the 0W-30 motor oil.
It’s the viscosity or “flowability” or thinness of any oil that determines its fuel economy improvement capacity. The 0W-30 is thinner or less viscous than the 5W-30 which makes it considered as better for saving more.
This is not to say 5W-30 does not increase the fuel economy, but it does lesser than 0W-30 motor oil. Compared to other high viscosity oils, the 5W-30 can improve the fuel economy. You can have 1 to 2 percent raise in fuel economy with 0W-30 motor oil.
Temperature Range
Generally, all lubricants have a temperature range in which they can operate. Increased velocity under lower temperature may be a restrictive condition for a motor oil to function effectively. A higher temperature and a lower velocity may cause a reduced thickness which may cause damage to the machine parts.
The suitable temperature range for 0W-30 motor oil is a flow up to -30 degree Celsius while that of 5W-30 is a flow up to -25 degree Celsius.
