20w40 vs 10w40: Which Viscosity is The Best for Your Engine in Winter?

A Quick Comparison Between 20W40 VS 10W40 Engine Oil

Take a quick look at the key comparison between 20W40 and 10W40 oil before going deep into the comprehensive discussion:

Property	20W40	10W40
Viscosity	High viscosity level at any weather condition	Low viscosity level at any weather condition
Cold Weather Performance	It may not help the engine to start quickly and also doesn’t offer good engine performance	Help the engine to start quickly and provide good engine performance
Hot Weather Performance	Offers better lubrication and engine performance	Offers moderate lubrication and engine performance than 20W40
Fuel Consumption	As thicker oil increases fuel economy	Offers better fuel economy
Friction and Wear	Provides better protection for the engine’s components at high temperatures, which can reduce engine wear	Creates less friction, but more wear on the engine compared to the 20W40
Price	More pocket-friendly	Slightly expensive
Recommended use	Warm climates and heavy-duty applications	All climates, but especially cold climates

What Do 20W40 and 10W40 Engine Oil Mean?

The numbers on motor oil viscosity grades like 20W40 and 10W40 indicate their thickness at different temperatures.

The first number represents viscosity in very cold temperatures, while the second number is viscosity in hot conditions.

A ‘20’ on the front of 20W40 means it flows like a SAE20 oil when cold. Thinner oil is needed at sub-zero temperatures for easy starting and engine protection when cold.

It means ‘20’ is a lot thicker for engines in the cold winter. However, old engines, infrequently driven vehicles, diesel engines, modified engines, etc., may need thick oil in winter.

Meanwhile, the ‘40’ on the end represents a thickness similar to a SAE40 at operating temperatures.

The ‘10’ number of 10W40 compared to 20W40 means it has slightly better flow in freezing conditions for easier starts. Both are multi-grade oils that provide year-round protection.

Their thicker viscosity at high engine temperatures is represented by the same 40 grade. It ensures adequate lubrication during rough driving or hot weather.

Key Differences Between 20W40 VS 10W40 Engine Oil

The differences between 20W40 and 10W40 lie in their characteristics. Here are some common differences between these oils:

1.Viscosity Ratings and Temperature Performance

Generally, both of these oils will offer the same viscosity index in warm temperatures. In fact, 20W40 engine oil may perform better than 10W40 oil in hot temperatures.

However, in cold weather conditions, you need thin oil for the oil to spread evenly and help the engine fight against frigid weather. In that case, 10W40 has smooth lubrication and less friction than 20W40.

Here is an approximate suitable temperature for these oils:

• 20W-40: -15°C to 45°C             
• 10W-40: -25°C to 40°C

2. Engine Compatibility

Both 20W40 and 10W40 oils are multi-grade oils suitable for various engines. The 10W40 engine oil is best suited for gasoline engines, including passenger cars, SUVs, and motorcycles.

In contrast, the 20W40 oil is primarily recommended for the engine of older vehicles, agricultural equipment, and specific industrial applications.

3. Fuel Economy

When you drive your car, the engine components need oil from the oil pan. Thick oils like 20W40 struggle to pump the oil smoothly throughout the engine. As a result, the engine uses more fuel to keep it optimal.

But the 10W40 oil is comparatively thinner compared to 20W40. Thus, pumping oil from the oil pan is relatively easier for the engine. Consequently, 10W40 has improved fuel economy than 20W40.

4. Lifespan

The thickness of the 20W40 oil causes it to break down quicker than the 10W40. Thus, you may need to change the oil every 5000 to 7000 miles. On the contrary, change the 10W40 oil every 8000 to 10000 miles.

5. Price

There is a small price difference between these two oils, a dollar per quart.

Generally, the 10W40 is a more popular choice than the 20W40, which makes the price of it higher than the 20W40. It means 20W40 oil is an affordable oil option, and the 10W40 is a little expensive.

On average, the 10W40 engine will cost you around $28, and the 20W40 engine oil cost around $26.

Which One Should You Pick Between 20W40 and 10W40?

The best way to choose between 20W40 and 10W40 engine oil is to consult your owner’s manual. The owner’s manual will recommend a specific oil viscosity based on your car’s engine and climate.

However, here’s a general guide to help you choose the right oil:

• If you live in a cold climate, you should choose 10W40. And if you live in a warm climate, you should choose 20W40.
• In case you’re a frequent highway driver, 10W40 oil is a good choice. And you should pick 20W40 oil for a truck or SUV, and other heavy-duty applications.

If you have a high-end engine, 20W40 oil is a good choice. And you should pick 10W40 for old, modified, gasoline, and diesel engines.

FAQs

Here are some common questions we often hear from people:

Q: Can I switch from 20W40 to 10W40 or vice versa?

Yes, you can switch between 20W40 and 10W40 oils as long as they meet the manufacturer’s specifications for your engine.

Q: Which oil is better for towing or heavy-duty use?

Both 20W40 and 10W40 oils can provide sufficient protection for towing or heavy-duty use. But 20W40 is a better choice in this case.

Q: What happens if you mix 20W40 with 10W40 oil?

Mixing 20W40 with 10W40 oil is generally acceptable, but it alters the resulting viscosity depending on the mixing ratio. Thus, it’s better to use one specific viscosity grade for optimal performance.