Is It Necessary to Use Fully Synthetic Oil for an Old Jetta?

[SanRachel]

It is not necessary to use fully synthetic oil for an old Jetta. Due to engine aging, using fully synthetic oil may cause the engine to become noisier and result in insufficient oil pressure, as fully synthetic oil has a lower viscosity. It is not recommended to use 5W-30 or 0W-40 oil; instead, 10W-40 or 15W-40 oil is more suitable. Below are relevant details about oil selection: Oil Selection: Naturally aspirated engines have relatively modest requirements for oil quality and can use mineral oil or semi-synthetic oil. If the owner has a higher budget, fully synthetic oil can be considered. Compared to naturally aspirated engines, turbocharged engines have a more compact structure and operate under harsher conditions, requiring higher-performance oil with better fluidity. Fully synthetic oil is the best choice for such engines. Brand Selection: When choosing a lubricant brand, if long-lasting performance is a priority, Mobil lubricants are a good option. For those who prioritize the oil's engine-cleaning capabilities, Shell oil is recommended. If strong oil film toughness is needed, Castrol can be chosen. For example, turbocharged engines are prone to carbon deposits during high-speed operation, so Shell oil, known for its strong cleaning ability, is a suitable choice.