Putting 5W40 Instead Of 5W20 – Your Comprehensive Guide To Engine Oil

ByRobert Lozano

This guide explores the implications of putting 5w40 instead of 5w20 in your engine. We’ll delve into the science of oil viscosity, potential benefits, common problems, and best practices to ensure your engine’s longevity and performance. Understand the risks and make informed decisions for your vehicle.

Ever found yourself staring at the oil aisle, wondering if a different viscosity could benefit your ride, perhaps even considering putting 5w40 instead of 5w20?

It’s a common dilemma for many car owners and DIY mechanics, especially when faced with specific driving conditions or an aging engine. We promise to cut through the confusion and provide clear, expert insights into what happens when you deviate from your manufacturer’s recommended oil.

By the end of this guide, you’ll understand the science behind engine oil, the potential advantages and disadvantages of such a switch, and how to make the best decision for your vehicle’s health and performance.

Understanding Engine Oil Viscosity: 5W20 vs. 5W40

Before we dive into the specifics of putting 5w40 instead of 5w20, let’s clarify what those numbers mean. Engine oil viscosity is a measure of its resistance to flow.

The “W” stands for winter, indicating the oil’s cold-start performance. The number before the “W” (e.g., 5W) represents the oil’s viscosity at cold temperatures.

A lower number means the oil flows more easily when cold, allowing for quicker lubrication during startup. Both 5W20 and 5W40 share the same cold-weather viscosity, meaning they perform similarly on a cold start.

The Hot-Temperature Viscosity Explained

The second number (20 or 40) indicates the oil’s viscosity at normal operating temperatures (typically 100°C or 212°F). This is where the significant difference lies.

  • 5W20: This is a “thinner” oil at operating temperature. It flows more freely, reducing internal engine drag and contributing to better fuel economy.

  • 5W40: This is a “thicker” oil at operating temperature. It maintains a higher viscosity under heat and pressure, which can provide a more robust oil film between moving parts.

Modern engines are often designed with tighter tolerances and rely on thinner oils like 5W20 for optimal performance and efficiency.

Why Manufacturers Specify 5W20: Modern Engine Design

Most modern vehicles, especially those from the last two decades, recommend 5W20 or similar low-viscosity oils. This isn’t just a random choice; it’s a carefully engineered decision.

Today’s engines feature incredibly tight clearances between moving parts. Thinner oils can penetrate these spaces more effectively, ensuring rapid lubrication from the moment you turn the key.

This rapid flow reduces wear during startup, which is when most engine wear occurs. Additionally, lower viscosity oils reduce parasitic drag within the engine.

Less drag means less energy is wasted overcoming internal friction, translating directly into improved fuel efficiency and, in some cases, slightly increased horsepower. Vehicle manufacturers design engines specifically for these characteristics.

The Implications of Putting 5W40 Instead of 5W20: What Changes?

When you consider putting 5w40 instead of 5w20, you’re essentially choosing a thicker oil for an engine designed for a thinner one. This switch can lead to several changes in engine behavior and long-term health.

The primary concern revolves around the oil’s ability to flow and lubricate effectively within the engine’s designed clearances.

Oil Flow and Lubrication Challenges

A thicker oil, like 5W40, might struggle to properly circulate through the narrow oil passages and hydraulic components (like variable valve timing systems or hydraulic lifters) found in engines designed for 5W20.

This reduced flow can lead to inadequate lubrication, especially in critical areas, increasing wear over time. It can also affect the operation of these sophisticated systems.

For example, if your engine uses variable valve timing (VVT), the thicker oil might slow down the response of the VVT actuators, potentially causing error codes or reduced engine performance.

Increased Engine Stress and Reduced Efficiency

The engine has to work harder to pump a thicker oil, which increases internal resistance. This extra effort translates to a slight decrease in fuel economy and potentially a small reduction in horsepower.

Over time, this increased stress can lead to higher operating temperatures and accelerate wear on the oil pump. The engine’s cooling system might also face a slightly increased load.

For off-roaders and those who push their vehicles, understanding this trade-off is crucial for maintaining performance and reliability.

Potential Benefits and Scenarios for Using 5W40

While generally not recommended for modern engines, there are specific, limited scenarios where putting 5w40 instead of 5w20 might be considered, often in older or heavily modified vehicles.

These situations typically involve engines that are showing signs of wear or are operating under extreme conditions that might cause thinner oils to break down.

Older, High-Mileage Engines

As engines age and accumulate miles, internal components can wear, leading to slightly larger clearances between parts. In such cases, a thicker oil like 5W40 might help.

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It can fill these larger gaps more effectively, potentially reducing oil consumption and quieting engine noise from worn components.

However, this is often a band-aid solution, and addressing the root cause of wear is always the best approach. Consult your mechanic for a proper diagnosis.

Extreme Operating Conditions

If you regularly operate your vehicle in extremely hot climates, tow heavy loads, or engage in demanding off-road activities, your engine oil will experience higher temperatures and increased stress.

Under these conditions, a 5W20 oil might thin out excessively, potentially compromising its lubricating film. A 5W40 oil could maintain a more robust film, offering better protection against metal-on-metal contact.

This is particularly relevant for off-road enthusiasts who subject their vehicles to prolonged high-RPM, low-airflow situations. Always check your owner’s manual for severe service recommendations.

Engines with Excessive Oil Consumption

If your engine is burning or leaking a significant amount of 5W20 oil, switching to a slightly thicker 5W40 might temporarily reduce consumption.

The thicker oil is less likely to seep past worn piston rings or valve seals. Again, this is a symptomatic treatment, not a cure for underlying mechanical issues.

A proper diagnostic should be performed to identify the cause of oil consumption. Putting 5w40 instead of 5w20 tips in this scenario often involves monitoring consumption closely after the switch.

Common Problems and Risks of Using Thicker Oil

Despite potential niche benefits, the risks associated with putting 5w40 instead of 5w20 in an engine not designed for it are significant and often outweigh any perceived advantages.

Understanding these common problems is crucial for anyone considering such a change, as they can lead to costly repairs and reduced engine lifespan.

Increased Engine Wear and Reduced Lubrication

The most critical risk is inadequate lubrication. Engines designed for 5W20 have tighter tolerances and smaller oil passages.

A thicker 5W40 oil may not flow quickly enough to critical engine components, especially during startup or high-RPM operation. This can lead to increased friction and accelerated wear on bearings, camshafts, and other vital parts.

Over time, this wear can significantly shorten your engine’s life. This is one of the most significant common problems with putting 5w40 instead of 5w20.

Decreased Fuel Economy and Performance

As mentioned, a thicker oil creates more internal drag. Your engine has to work harder to pump and move the oil, consuming more energy.

This translates directly to a noticeable decrease in fuel efficiency and potentially a slight reduction in horsepower. While seemingly minor, these losses add up over the vehicle’s lifespan.

For everyday drivers, this means more trips to the pump and higher operating costs.

Potential for Check Engine Lights and System Malfunctions

Many modern engines rely on specific oil pressures and flow rates for systems like variable valve timing (VVT), hydraulic lifters, and even turbocharger lubrication.

A thicker oil can disrupt these delicate balances, causing improper operation or delayed responses. This can trigger a “Check Engine” light, indicating a fault within these systems.

Ignoring these warnings can lead to further damage to expensive components. This highlights why following the putting 5w40 instead of 5w20 guide carefully is essential.

Warranty Invalidation

Perhaps the most immediate and significant risk for newer vehicles is the potential to void your manufacturer’s warranty. Using an oil viscosity not specified in your owner’s manual is often grounds for denying warranty claims related to engine damage.

Always consult your vehicle’s owner’s manual before making any changes to recommended fluids. This is a critical aspect of putting 5w40 instead of 5w20 best practices.

Best Practices and Decision-Making for Your Engine

When considering any deviation from your manufacturer’s recommendations, informed decision-making is paramount. Here are some putting 5w40 instead of 5w20 tips and best practices.

Consult Your Owner’s Manual First

Your vehicle’s owner’s manual is the ultimate authority on recommended oil viscosity. It often provides alternative recommendations for severe service conditions or specific temperature ranges.

Always check this resource first. If it doesn’t explicitly allow for 5W40, proceed with extreme caution.

Monitor Engine Performance Closely

If you do decide to switch to 5W40 (e.g., in an older, high-mileage engine with known oil consumption issues), monitor your engine’s performance diligently.

Look for changes in oil pressure, fuel economy, engine noise, and any dashboard warning lights. Check your oil level frequently.

Any negative changes should prompt an immediate return to the recommended oil viscosity.

Consider a Professional Opinion

When in doubt, consult a trusted mechanic or an automotive expert. They can assess your engine’s specific condition, driving habits, and recommend the best course of action.

A professional can also help diagnose underlying issues that might be prompting you to consider a thicker oil.

The “How To” of Changing Oil

If you decide to proceed with changing your oil, the process for how to putting 5w40 instead of 5w20 is the same as any other oil change:

  1. Gather your tools: Socket wrench, oil filter wrench, drain pan, new oil filter, funnel, and of course, the new oil.

  2. Warm up the engine: Drive for a few minutes to get the oil flowing, then park on a level surface.

  3. Drain the old oil: Place the drain pan under the oil pan, remove the drain plug, and allow all the oil to flow out. Replace the drain plug with a new washer.

  4. Replace the oil filter: Use the oil filter wrench to remove the old filter. Apply a thin film of new oil to the gasket of the new filter before screwing it on hand-tight, then an additional quarter to half turn with the wrench.

  5. Add new oil: Using a funnel, pour the specified amount of 5W40 oil into the engine’s oil fill cap.

  6. Check level and start engine: Let the oil settle, then check the dipstick. Start the engine, let it run for a minute to circulate oil, then shut it off and recheck the dipstick, topping off if necessary.

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Always dispose of used oil responsibly at a certified recycling center.

Sustainable Oil Choices and Environmental Considerations

Beyond viscosity, modern engine oils also factor into environmental sustainability. When considering any oil change, including putting 5w40 instead of 5w20, think about the broader impact.

Many conventional oils are petroleum-based, while synthetic and semi-synthetic options offer enhanced performance and often longer drain intervals, reducing overall oil consumption.

Synthetic vs. Conventional Oils

  • Synthetic Oils: These are engineered to provide superior performance, especially in extreme temperatures. They resist breakdown better and can extend oil change intervals, contributing to less waste. They are often a more sustainable putting 5w40 instead of 5w20 choice due to their longevity.

  • Conventional Oils: These are refined from crude oil and are generally less expensive. However, they break down faster and require more frequent changes, generating more used oil.

Opting for a high-quality synthetic oil, regardless of viscosity, is often a more eco-friendly putting 5w40 instead of 5w20 practice, as it reduces the frequency of oil changes and the associated waste.

Proper Disposal of Used Oil

No matter what oil you choose, proper disposal is critical. Never pour used oil down drains or onto the ground. One gallon of motor oil can contaminate one million gallons of fresh water.

Collect used oil in a sealed container and take it to an authorized recycling center or auto parts store that accepts used oil. This is a vital part of any putting 5w40 instead of 5w20 care guide.

Frequently Asked Questions About Putting 5W40 Instead of 5W20

Can I mix 5W40 with 5W20 oil?

While generally not recommended, mixing different viscosities of the same type (e.g., synthetic with synthetic) won’t cause immediate engine damage. However, it will result in an oil with an unpredictable viscosity that is somewhere between the two. It’s always best to use a single, recommended viscosity.

Will 5W40 cause my engine to overheat?

A thicker oil like 5W40 can cause the engine to work harder, generating slightly more heat. In engines designed for 5W20, this increased heat, combined with potentially reduced oil flow to critical components, could exacerbate existing cooling system issues or contribute to higher operating temperatures. However, it’s unlikely to be the sole cause of overheating unless other problems exist.

How quickly will I see problems if I use the wrong oil?

The effects can vary. Some issues, like a slight drop in fuel economy or a “Check Engine” light, might appear relatively quickly. Long-term problems like accelerated engine wear or component damage due to inadequate lubrication might take thousands of miles to manifest. It’s why early detection and monitoring are key.

Is 5W40 better for high-performance driving or racing?

For high-performance or racing applications, specific engine designs and extreme operating conditions might indeed benefit from a thicker oil like 5W40, or even higher. However, these engines are often built with different tolerances and oiling systems to accommodate such oils. For a stock engine designed for 5W20, sticking to the manufacturer’s recommendation is almost always the safest bet.

What if my vehicle is older but still recommends 5W20?

Even if your vehicle is older, if the manufacturer still specifies 5W20, it’s generally best to stick with it. Unless your engine is exhibiting significant wear, oil consumption, or you operate under severe, consistent conditions (and your manual provides an alternative), deviating can introduce more problems than it solves. Always prioritize the manufacturer’s guidance first for the best putting 5w40 instead of 5w20 care guide.

Ultimately, the decision to use 5W40 instead of 5W20 is not one to be taken lightly. For most modern vehicles, sticking to the manufacturer’s recommended viscosity is the safest and most effective way to ensure engine longevity, optimal performance, and fuel efficiency.

While there are niche scenarios for older or heavily stressed engines, these require careful consideration, monitoring, and often professional advice. Prioritize your engine’s health and your vehicle’s long-term reliability.

Stay informed, choose wisely, and keep your engine running smoothly for miles to come!

Robert Lozano
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