oil viscosity VOLKSWAGEN PASSAT 2009 Owners Manual

Adjust the tire pressure
The proper tire pressure helps reduce rolling resistance as well as fuel consumption.
When purchasing new tires, always make sure that the tires are optimized for lower rolling resistance.
Use low viscosity engine oil
Fully “synthetic,” low viscosity engine oils that expressly comply with Volkswagen oil quality standards reduce fuel consumption. Low viscosity engine oils reduce the frictional resistance on the engine and are distributed more evenly and quickly, particularly when cold-starting the engine. The effect is particularly apparent in vehicles that frequently travel short distances.
Always ensure the right engine oil level is maintained and keep to the scheduled service intervals (engine oil changes).
Make sure the engine oil that you purchase expressly complies with Volkswagen oil quality standards and is the oil approved by Volkswagen for your vehicle.
Avoid unnecessary weight
The lighter the vehicle, the more economical and eco-friendly it will be. For example, an extra 220 lbs (100 kg) of weight increases fuel consumption by up to 1 pint per 60 miles (0.3 l/100 km).
Remove all unnecessary items and unnecessary dead weight from the vehicle.
Remove unnecessary aftermarket components
The more aerodynamic the vehicle, the less fuel it will consume. Aftermarket components such as bicycle racks reduce its aerodynamic performance.
Therefore, remove unnecessary structures and unused rack systems, particularly if planning to drive at higher speeds.

Engine oil quality is based not only on requirements for engines and exhaust treatment systems, but also on fuel quality. Engine oil comes into contact with fuel and fuel residue in all internal combustion engines, causing engine oil to age and its lubricating qualities to deteriorate.
Your engine was factory-filled with a high-quality, “synthetic” all-season engine oil that meets strict Volkswagen oil quality standards and has a viscosity grade of SAE 5W-40. or SAE 5W-30. You can use this oil for normal driving in all temperatures.
If you need to add oil between oil changes, use only a high quality oil that expressly complies with the Volkswagen oil quality standard specified for your vehicle's engine:

Engines Engine oil specification
Gasoline engines VW 504 00, VW 503 00, VW 502 00
Diesel engines VW 507 00
At the time this Manual was printed, the engine oils available in the U.S. that meet these Volkswagen standards are “synthetic” oils. This does not mean, however, that any “synthetic” engine oil will meet Volkswagen standards. Always use an approved oil that expressly complies with the Volkswagen oil quality standard that applies to your vehicle's engine.
General recommendations:
If “synthetic” oil that meets the applicable Volkswagen oil quality standard with viscosity grade SAE 5W-40 or SAE 5W-30 is not available in your area, be sure to use a viscosity grade suitable for the climate, season, and operating conditions that exist where the vehicle is used. Make sure the oil meets the quality standard listed in table.
Engine oils are constantly being improved. Authorized Volkswagen dealers and authorized Volkswagen Service Facilities are always up-to-date regarding new developments and changes. Volkswagen therefore recommends that you have the engine oil changed by an authorized Volkswagen dealer or an authorized Volkswagen Service Facility.
NOTICE
x If you need to add oil and there is none available that meets the Volkswagen oil quality standard your engine requires, you may add a total of no more than 1/2 quart (0.5 liter) of a high-quality “synthetic” oil that meets ACEA A3 specifications and has a viscosity grade of SAE 5W-40 or SAE 5W-30.
x Use only a high quality engine oil that expressly complies with the Volkswagen oil quality standard specified for your vehicle's engine. Using any other oil can cause serious engine damage that will not be covered by any Volkswagen Limited Warranty.
x Do not mix any lubricants or other additives into the engine oil. Doing so can cause engine damage! Damage caused by these kinds of additives are not covered by any Volkswagen Limited Warranty.
Engine oil capacities