Can You Mix Synthetic Oil With Regular Oil?

Synthetic oil and conventional oil are two prevalent engine oil varieties utilized in vehicles. Synthetic oil is engineered from chemical compounds, whereas regular oil is derived from crude oil. An inquiry that commonly emerges is whether it’s safe to blend these two oil types.

As per multiple sources, it’s generally deemed safe to mix synthetic oil with conventional oil. Nonetheless, the recommendation is to employ a consistent oil type throughout the engine’s lifespan to ensure optimal performance. In cases where blending becomes necessary, adhering to the same oil weight or viscosity specified in the owner’s manual is imperative. Merging different viscosity grades can potentially undermine the oil’s capacity to lubricate and safeguard the engine.

What is Synthetic Oil?

Synthetic oil stands as a specialized lubricant composed of artificially engineered chemical compounds. Crafted to outperform conventional oils, synthetic oil offers heightened protection and performance. While it typically comes at a higher cost than regular oil, it comes with a range of advantages.

A key merit of synthetic oil lies in its ability to endure elevated temperatures, surpassing the capabilities of conventional oil. This translates to enhanced engine safeguarding, especially in extreme scenarios. Additionally, synthetic oil boasts a more consistent viscosity, enabling it to maintain optimal performance across a broader temperature spectrum.

Another edge of synthetic oil is its extended lifespan compared to conventional oil. This extended life interval between oil changes can lead to time and monetary savings in the long term. However, it’s essential to acknowledge that the precise duration between oil changes hinges on diverse factors, encompassing driving habits and vehicle type.

In sum, synthetic oil proves a prudent choice for those seeking top-tier engine protection and performance. Nevertheless, it’s worth noting that the quality of synthetic oils can vary, underscoring the importance of selecting a reputable product tailored to your specific vehicle.

What is Regular Oil?

Conventional oil, often referred to as regular oil, stands as the prevailing lubricant utilized in vehicles. Sourced from crude oil, it encompasses a blend of base oils and additives. These constituents work in tandem: the base oil facilitates lubrication, while the additives enhance the oil’s performance by curbing engine wear and thwarting corrosion.

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Varied viscosities characterize regular oil, quantified using the Society of Automotive Engineers (SAE) rating system. This rating system determines the oil’s thickness and flow characteristics at different temperatures. Lower numbers correspond to thinner oil, excelling in cold temperatures, while higher numbers denote thicker oil, better suited for high-temperature performance.

Regular oil serves as a fitting choice for most vehicles and is particularly recommended for engines with modest mileage. It holds the advantage of being more cost-effective than synthetic oil, catering to budget-conscious individuals. Nevertheless, it necessitates more frequent oil changes compared to synthetic oil, typically spanning 3,000 to 5,000 miles.

In summary, regular oil presents a dependable and budget-friendly avenue for upholding your vehicle’s engine vitality.

Can You Mix Synthetic Oil With Regular Oil?

Yes, it is indeed safe to combine synthetic oil with regular oil. Nonetheless, it’s essential to recognize that the advantages associated with synthetic oil might diminish when blended with conventional oil. The inclusion of regular oil can compromise the performance potential of the synthetic oil.

For optimal results, it is advisable to adhere to the oil viscosity specified in your vehicle’s owner’s manual. Mixing oils of different viscosities could potentially lead to engine issues and a decrease in overall performance. If you find yourself uncertain about the appropriate oil viscosity to use, consulting your owner’s manual or seeking advice from a professional mechanic is recommended.

When it comes to topping up your oil levels, there’s no harm in blending synthetic and regular oil. However, if you’re conducting a complete oil change, it is best practice to stick with a consistent oil type. Blending different oil types during a full oil change can contribute to engine problems and a reduction in performance.

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Effects of Mixing Synthetic and Regular Oil

Combining synthetic and regular oil is generally considered safe for your engine, yet it can yield several effects. According to information from Jiffy Lube, the introduction of regular oil into a blend with synthetic oil can lead to a reduction in the performance capabilities of the synthetic variant. Furthermore, the additives present in the oil, which include detergents and viscosity enhancers, might undergo changes that diminish their ability to safeguard your engine effectively.

An additional consequence of mixing synthetic and regular oil involves potential alterations in the oil’s viscosity. Synthetic oil possesses a different viscosity profile compared to regular oil. Consequently, when these two oils are combined, the resultant blend could exhibit a viscosity level unsuitable for your engine’s needs. Such a scenario may compromise the oil’s capacity to provide optimal lubrication for your engine’s moving components, potentially causing gradual damage over time.

It’s essential to recognize that the amalgamation of synthetic and regular oil could impact your engine’s warranty as well. If your warranty mandates the usage of synthetic oil exclusively, the introduction of regular oil might invalidate your warranty. To ensure the best oil choice for your engine’s well-being and warranty stipulations, it’s advisable to consult your owner’s manual or seek guidance from a qualified mechanic.

Recommendations for Mixing Oils

Blending synthetic oil with regular oil is typically safe, yet a few key considerations are worth heeding. Here are some guidelines for effectively mixing oils:

Refer to your owner’s manual: Prior to blending oils, consult your owner’s manual to determine the recommended oil type and weight. Adhering to the prescribed weight and viscosity will help safeguard your engine from potential damage.

Incorporate small amounts: If topping off your oil is necessary, incorporating small quantities of synthetic or regular oil is acceptable. However, it’s advisable to refrain from mixing large volumes, as this can potentially compromise the oil’s performance and benefits.

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Avoid combining oils with varying additives: Blending oils containing dissimilar additives can trigger chemical reactions that might harm your engine. Opt for oils with comparable additives or consider using a premium synthetic blend formulated to harmonize with different oil types.

Contemplate a complete oil change: If uncertainty surrounds oil mixing, ponder undergoing a full oil change. This approach ensures your engine consistently operates with a uniform oil type and weight.

Keep oil levels under observation: After blending oils, closely monitor your oil levels to ensure your engine functions smoothly. If any anomalies arise, such as heightened engine noise or diminished performance, it’s recommended to arrange for an oil change promptly.

In essence, pairing synthetic oil with regular oil can be done safely, provided these recommendations are followed, and high-quality oils intended for co-use are employed.


Combining synthetic and regular oil is safe, but adhering to certain guidelines is essential. Mixing oils is acceptable under specific circumstances, such as topping off oil levels or transitioning from conventional to synthetic oil. However, frequent oil mixing is discouraged due to its potential to compromise synthetic oil’s performance.

When blending oils, it is crucial to employ the same viscosity and weight as advised in your owner’s manual. This practice ensures optimal oil function and the requisite engine protection.

While mixing oils is a safe option, it remains advisable, when feasible, to opt for full synthetic oil. Synthetic oil outperforms conventional oil in terms of both performance and protection. Nonetheless, if your vehicle requires conventional oil or is of an older model, you can still safely mix oils, provided you adhere to the recommended guidelines.