Which Oil Should I Use for My Car? A Guide to 5W30, 10W40, and Other Oil Grades.

Choosing the right engine oil is one of the most important decisions for your car’s longevity. Many drivers ask: which oil should I use for my car? What do oil markings like 5W30, 10W40, or 0W20 really mean, and does using the wrong oil actually harm the engine?

In this guide, we explain engine oil grades, viscosity ratings, and manufacturer approvals in simple terms—so you can confidently choose the correct oil for your vehicle.

What Do Oil Markings Like 5W30 or 10W40 Mean?

Engine oil labels follow a standardized viscosity classification defined by SAE (Society of Automotive Engineers). The most common examples are 5W30, 10W40, or 0W20.

Breaking it down:

• The number before “W” (Winter)
  Indicates how the oil behaves at low temperatures.
  • Lower number = better cold starts
  • Example: 0W or 5W flows better in winter than 10W
• The number after “W”
  Shows oil thickness at normal engine operating temperature (around 100°C / 212°F).
  • Higher number = thicker oil at high temperatures
  • Example: 40 protects better under heavy load than 30

Example:
👉 5W30 works well in cold starts and provides adequate protection at normal temperatures — that’s why it’s so popular in modern cars.

5W30 vs 10W40 – What’s the Difference?

5W30 is typically recommended for newer vehicles, especially those with turbochargers, direct injection, or start-stop systems.

10W40 is often used in older engines or cars with higher mileage, where tighter tolerances are no longer critical.

🔧 Important: Even if two oils seem similar, always follow your manufacturer’s recommendation.

How to Choose the Right Oil for Your Car

1. Check the Owner’s Manual

This is always your primary source. Manufacturers specify:

• viscosity (e.g. 5W30)
• oil standard (ACEA, API)
• brand-specific approvals (VW, BMW, Mercedes, Ford, etc.)

2. Follow Manufacturer Oil Approvals

Examples include:

• VW 504.00 / 507.00
• BMW Longlife-04
• MB 229.51
• Ford WSS-M2C913-D

These approvals ensure the oil works correctly with your engine design, emissions system, and service intervals.

3. Consider Your Driving Conditions

• City driving & short trips → lower viscosity, more frequent changes
• Highway driving → standard intervals work well
• Hot climate or heavy loads → higher high-temperature rating (e.g. “40”)

Mineral, Semi-Synthetic, or Fully Synthetic Oil?

Mineral Oil

• Cheapest option
• Suitable for older engines
• Shorter oil change intervals

Semi-Synthetic Oil

• Balanced performance and price
• Common in mid-age vehicles

Fully Synthetic Oil

• Best protection and stability
• Ideal for modern engines and turbochargers
• Longer service life

🧰 Pro tip: Most modern cars require fully synthetic oil—using mineral oil may cause long-term damage.

Can You Use a Different Oil Than Recommended?

Short answer: you shouldn’t.

Using the wrong oil can result in:

• poor lubrication
• increased fuel consumption
• faster engine wear
• damage to turbochargers or timing chains
• clogged particulate filters (DPF)

In emergency situations, topping up with a similar oil is acceptable, but a full oil change should follow as soon as possible.

Does Engine Mileage Affect Oil Choice?

Yes. High-mileage engines (150,000+ miles / 240,000+ km) may benefit from:

• slightly thicker oil (e.g. switching from 5W30 to 5W40)
• oils designed for high-mileage engines with seal conditioners

Always consult a mechanic before changing viscosity.

Popular Oil Grades and Their Typical Use

Summary – Which Oil Should You Use for Your Car?

To choose the correct engine oil:

1. Follow the manufacturer’s specifications
2. Use the correct viscosity grade
3. Check required approvals
4. Match oil type to engine age and driving style
5. Never downgrade oil quality to save money

🛠️ In one sentence:
The right engine oil is the one that meets your manufacturer’s specifications—not just the one with the right numbers on the bottle.