Motor Oil Showdown: Conventional vs Synthetic Blend vs Full Synthetic

Key Takeaways

  • Conventional oil is made from crude oil and provides basic lubrication for engine parts. It’s affordable but needs changing more frequently.
  • Synthetic blend oil combines synthetic and conventional base oils to offer improved performance at a moderate cost. It lasts longer than conventional oil.
  • Full synthetic oil is entirely lab-made and engineered to maximize engine protection. It outperforms conventional and synthetic blends but costs more upfront.
  • Use conventional oil for older, high-mileage vehicles. Synthetic blend is a step up for most drivers. Full synthetic is ideal for newer engines and severe driving.
  • Follow your owner’s manual for oil type and change interval recommendations. Properly maintaining your engine oil is vital for performance and longevity.

Selecting the right motor oil is critical to engine health and longevity. With various options available, ranging from conventional to full synthetic formulations, choosing the optimal oil for your vehicle can get confusing. Understanding the key differences between conventional, synthetic blend, and full synthetic oils will help you make an informed decision.

With this information, you’ll be able to pick the ideal oil for your vehicle based on factors like age, mileage, driving conditions, and maintenance needs.

Let’s get started!

Conventional Motor Oil

Conventional oil, also known as mineral oil, has been the standard engine lubricant for over a century.

It’s produced by refining crude oil to separate, purify, and improve the hydrocarbon molecules. The resulting conventional oil offers basic protection for internal engine components.


Conventional motor oil consists of base oils made from refined crude oil, along with additives intended to enhance certain properties. Common additives include:

  • Detergents – Clean engine internals by suspending oil sludge and deposits
  • Dispersants – Prevent soot and dirt from clumping together
  • Anti-wear additives – Form protective film to reduce friction and wear
  • Corrosion inhibitors – Combat rusting and corrosion
  • Antioxidants – Extend oil’s lifespan by reducing oxidation

Benefits of Conventional Oil

  • Affordable price – Significantly lower cost compared to synthetic or synthetic blend oils
  • Wide availability – Can be purchased at any auto parts store or service station
  • Suitable for high-mileage engines – Thicker oil provides extra protection for worn-out engine components
  • Trusted formula – Conventional oil has been used for over 100 years

Drawbacks of Conventional Oil

  • Requires frequent oil changes – Only lasts about 3,000-5,000 miles before turning sludgy
  • Poor cold flow properties – Thickens substantially in cold weather, leading to reduced fuel economy and increased engine wear
  • Breaks down rapidly at high temperatures – Accelerated oxidation and evaporation compared to synthetic oils
  • Increased engine deposits and sludge – Dirtier engines over time
  • Reduced fuel economy – Higher friction leads to lower MPG

Best Uses for Conventional Oil

  • Older engines without tight tolerances
  • High mileage vehicles over 75,000 miles
  • Cars driven infrequently or short distances
  • Drivers on a tight budget

Synthetic Blend Motor Oil

Synthetic blend oil contains a mixture of conventional and synthetic base oils, engineered to provide improved performance at moderate cost. The exact ratio of synthetic to conventional can vary by brand. Synthetic blends offer a compromise between full synthetics and conventional oils.


Synthetic blend oils blend conventional mineral oils with synthetic base stocks, usually at a ratio of 70/30 or 50/50. They also contain a robust additive package, including:

  • Detergents to capture more sludge
  • Dispersants to handle soot and prevent clumping
  • Friction reducers for increased engine efficiency
  • Anti-rust and anti-corrosion additives
  • Antioxidants to extend oil life

Benefits of Synthetic Blend Oils

  • Affordable price – Costs moderately more than conventional oil
  • Enhanced performance – Synthetic component improves cold flow, oxidation resistance, and deposit control
  • Extended drain intervals – Lasts up to 7,500 miles or more before oil change needed
  • Ideal for many newer engines – Meets requirements of most post-2000 automakers

Drawbacks of Synthetic Blends

  • Still contains refined crude oils – Doesn’t offer full benefits of 100% synthetic base
  • Quality varies by brand – No industry standard for the conventional/synthetic ratio
  • Costs more than conventional oil – Drivers seeking the lowest price may want conventional instead

Best Uses for Synthetic Blend Oils

  • Newer engines beyond break-in period
  • Most cars built from 1990 onward
  • Moderate mileage vehicles under 100k miles
  • Stop-and-go city driving
  • Towing and hauling

Full Synthetic Motor Oil

Full synthetic oil contains no crude oil components. Instead, it’s constructed entirely from synthesized hydrocarbons and custom additives to produce superior lubrication. Full synthetic costs more but provides the ultimate in engine protection.


  • Synthetic base oils – Lab-created molecules designed for specific properties. Types used include:
  • Synthetic hydrocarbons (PAO, GTL)
  • Esters
  • Polyalphaolefins (PAO)
  • Additive package – Most robust additive combinations for added protection

Benefits of Full Synthetic Oil

  • Superior cold flow – Better lubrication in frigid temperatures
  • Withstands extreme heat – Less evaporation and breakdown at high temperatures
  • Maximizes engine efficiency – Exceptional horsepower and fuel economy retention
  • Longest drain intervals – Up to 10,000+ miles between changes
  • Lower oil consumption – Synthetics burn off and evaporate less
  • Unsurpassed sludge and deposit control – Keeps engines spotless

Drawbacks of Full Synthetic Oils

  • Higher upfront cost – Synthetics cost 2-3X more per oil change compared to conventional
  • May increase oil leaks – Not always recommended for engines with existing leaks
  • Overkill for some vehicles – No benefit for low mileage, well maintained engines

Best Uses for Full Synthetic Oils

  • New vehicles under factory warranty
  • Performance cars and modified engines
  • Vehicles driven over 15,000 miles per year
  • Diesel engines and turbos
  • Extreme temperature conditions

How To Choose The Right Motor Oil

Picking the optimal conventional, synthetic blend, or full synthetic oil depends on your vehicle, driving habits, and maintenance preferences. Here are key factors to consider:

Age and Mileage

Newer, low mileage engines – Stick with full synthetic oils to maximize protection and efficiency. Follow manufacturer specifications.

Older engines above 75k miles – Conventional oil offers additional wear protection. Check for leaks first.

Moderate mileage cars – Synthetic blends provide a nice balance of quality and affordability.

Driving Conditions

Stop-and-go city driving – Synthetics withstand heat cycles and reduce sludge buildup.

Towing/hauling – Synthetic or synthetic blend oils resist viscosity breakdown from heavy loads.

High performance and modified engines – Full synthetics minimize power loss and deliver unbeatable protection.

Extreme hot or cold climates – Synthetics flow better when cold and withstand heat.

Maintenance Habits

Following factory change intervals – Take advantage of synthetic’s extended drain intervals.

Prefer less frequent changes – Conventional oil needs changing more regularly.

Seeking maximum engine cleanliness – Full synthetics deter sludge better than mineral oils.

Trying to prolong engine life – Synthetics sustain viscosity and minimize wear over time.

Budget Considerations

Seeking the lowest cost – Conventional oil changes are the most budget friendly.

Willing to spend more upfront – Synthetics save money in the long run through fewer changes and reduced wear.

Adding life to high mileage vehicle – Conventional may be the most cost effective option.

Protecting new car warranty – Splurge on full synthetic to get the most peace of mind.

Conventional vs. Synthetic vs. Synthetic Blend Oil Comparison

Conventional OilSynthetic BlendFull Synthetic
Base Oil SourceRefined crude oilMixture of conventional and synthetic100% lab-created synthetic base stocks
CompositionBasic mineral oil and minimal additivesUp to 70% conventional oil blended with <30% syntheticNo crude oil – fully synthetic base and additives
Cost Per Change$$$$-$$$$$$
Typical Change Interval3,000 miles5,000-7,500 miles7,500-10,000+ miles
Cold FlowPoor – thickens substantially at low tempsImproved over conventionalBest cold flow properties
High Temp StabilityFair – breaks down and evaporatesBetter resistance to oxidation at high heatHighest resistance to thermal breakdown
Engine Wear ProtectionBasicEnhancedMaximum
Sludge and DepositsFairGoodExcellent detergency
Best UsesOlder engines, high mileage, budget-minded driversMost modern engines, moderate conditionsNew cars, performance applications, extreme conditions

As you can see, full synthetic oils outperform in almost every category, while also allowing extended drain intervals.

However, conventional oil remains a viable lower-cost option for older engines and budget-minded drivers. Synthetic blends offer a middle ground.

Frequently Asked Questions

Is synthetic blend oil better than full synthetic?

No, full synthetic oil remains superior in terms of molecular engineering, high temperature stability, wear protection, and low temperature performance. However, a quality synthetic blend can offer 80-90% of the benefits of full synthetic for less cost.

Can you use full synthetic instead of synthetic blend?

Yes, you can safely use full synthetic oil in place of a synthetic blend. The fully synthetic base stocks and specialized additives will only enhance performance further. Just be aware that full synthetic is more expensive.

Does synthetic blend oil last longer than conventional?

Yes. Synthetic blend oils typically last anywhere from 50-100% longer than conventional oils until needing an oil change, thanks to the synthetic component’s improved stability. Most synthetic blends can go 5,000-7,500 miles between changes.

What are the disadvantages of synthetic blend oils?

  • Still contain crude oil components versus full synthetics
  • Quality and composition varies between brands
  • Cost more than conventional oil
  • Don’t last as long as full synthetics
  • May not offer full synthetic benefits in extreme cold or heat

When should you not use full synthetic oil?

Avoid full synthetics in these cases:

  • High mileage engines over 100k miles with existing leaks or consumption – the lower viscosity synthetic can increase seepage
  • Older engines designed for conventional oil before 1990 – seals may not handle synthetic
  • Engines explicitly advised against synthetic by the manufacturer
  • Unwillingness to follow extended oil change intervals


Understanding the key differences between conventional, synthetic blend, and full synthetic motor oils allows you to pick the optimal oil for your driving needs. Conventional oil remains an affordable option for older engines and basic maintenance. Synthetic blends offer improved performance at moderate cost, while full synthetics provide maximum protection yet cost more.

Follow your owner’s manual, choose an oil that fits your engine and conditions, and properly maintain change intervals. With the right oil, you can keep your engine running cleanly and efficiently for years to come. Don’t cut corners on oil quality and give your car the lubrication it deserves.

Frequently Asked Questions

What type of oil is best for older vehicles?

For older engines over 75,000 miles, conventional oil is often recommended. The heavier viscosity and anti-wear additives in conventional oil provide extra protection for high-mileage vehicles. The slower oil flow can help seal small leaks in worn seals and gaskets. Always check oil type recommendations in your owner’s manual.

When should you use synthetic blend oil?

Synthetic blends offer a nice balance of performance and affordability for many drivers. They are ideal for newer engines past the break-in period, vehicles under 100k miles, moderate driving conditions, and stop-and-go city driving. If you do mostly highway miles, conventional oil may be sufficient.

Do you have to use synthetic oil in a newer car?

Many automakers today recommend full synthetic oil for newer engines, especially during the warranty period. Synthetic oil allows for longer drain intervals and provides the best resistance to sludge, deposits, and wear. However, synthetic blends are fine for most newer cars if trying to balance cost. Refer to your manual.

Can synthetics damage engine seals?

In rare cases, the lower viscosity of synthetic oils can cause minor leaks in older engines already prone to seepage. Make sure there are no existing leaks or oil consumption issues before switching purely to minimize risk. Most modern engines are designed for synthetic use.

Is it OK to switch from conventional to synthetic oil?

Yes, you can safely switch from conventional to full synthetic or synthetic blend oils as they provide better protection. Ideally, do so at your next oil change interval. When adding synthetic to an older engine, double check for any pre-existing leaks or consumption issues first.

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