Use the oil specification your vehicle manufacturer requires.
If your vehicle requires synthetic oil or an oil meeting a specification that is commonly supplied as synthetic, use it. If the manufacturer permits conventional oil that meets every required viscosity and performance specification, conventional oil may be acceptable. The owner's information is the starting point.
Viscosity, performance specification, engine design and manufacturer requirements matter. Two oils with the same viscosity printed on the bottle may not necessarily meet the same specifications.
What is the actual difference?
Both types are formulated to lubricate, clean, cool and protect the engine. Conventional oil is based primarily on refined crude-oil base stocks, while synthetic oils use more highly processed or engineered base stocks and additive packages designed to provide controlled performance characteristics.
| Factor | Why Synthetic Is Common | Conventional Oil |
|---|---|---|
| Base oil | Highly refined or engineered base stocks formulated for consistent performance. | Primarily refined petroleum base stocks combined with an additive package. |
| Temperature performance | Often formulated for strong low-temperature flow and high-temperature stability. | Can perform properly when it meets the specifications required by the engine. |
| Turbocharged engines | Commonly required or specified for modern turbocharged applications. | Should only be used when it satisfies the vehicle manufacturer's exact requirements. |
| Cost | Typically costs more per oil change. | Often costs less where it remains an approved option. |
| Service interval | Follow the manufacturer's interval; synthetic does not automatically justify extending it. | Follow the manufacturer's interval and applicable severe-service schedule. |
| Best choice | Whichever oil meets every requirement specified for your particular engine. | |
Six things matter more than marketing on the bottle.
Use the required viscosity grade
Grades such as 0W-20, 5W-30 and others describe viscosity behavior. Use the grade or approved alternatives specified for the vehicle.
Look beyond viscosity
Manufacturers may require particular API, ILSAC, ACEA or manufacturer-specific performance specifications.
Engine design matters
Turbocharging, variable valve timing, emissions systems and internal tolerances can influence lubrication requirements.
Temperature affects oil behavior
The manufacturer may specify viscosity choices according to expected ambient temperature and operating conditions.
Operating conditions matter
Frequent short trips, towing, extensive idling and other severe-use conditions can affect the applicable maintenance schedule.
Follow documented requirements
Use oil that meets the specifications identified for your vehicle and retain maintenance records when appropriate.
Some vehicles require it. Others permit more than one option.
The answer depends on the specific engine—not simply the vehicle brand. Even two models from the same manufacturer can have different oil requirements.
- Check the owner's manual or digital owner's information
- Confirm the required viscosity grade
- Confirm required oil performance specifications
- Account for engine and model-year differences
- Follow severe-service guidance when applicable
- Use the correct oil filter for the application
- Do not assume high mileage changes the specification
- Ask before substituting a different oil type or grade
Switching to a cheaper oil that does not meet the required specification is not a worthwhile shortcut. The lubricant is part of the engine's design requirements.
Modern engines place demanding requirements on lubricants.
Synthetic oils are widely used because formulations can be engineered for strong performance across temperature extremes, resistance to oxidation and demanding operating conditions. This is especially relevant as manufacturers use turbocharging, tighter engine tolerances and sophisticated emissions and valve-control systems.
The label alone does not tell you whether an oil is correct for your engine. Always confirm viscosity and required performance approvals.
Should an older car switch to synthetic oil?
Age or mileage alone does not automatically prohibit synthetic oil. What matters is whether the oil meets the engine's requirements and whether there are existing mechanical concerns such as leakage or excessive oil consumption.
“High-mileage” oils may contain additive packages marketed toward older engines, but they do not repair worn seals, internal wear or mechanical oil leaks. If your vehicle is losing oil, diagnose the cause rather than relying on a different oil label as the repair.
Can you switch between conventional and synthetic oil?
For many engines, switching oil types is not inherently a problem as long as the replacement oil meets all requirements for the vehicle. However, if synthetic oil is required, switching to a conventional product that does not meet the specification is not appropriate.
Conventional to synthetic
Generally possible when the synthetic product meets the required viscosity and specifications.
Synthetic to conventional
Only appropriate when a conventional oil actually meets all requirements specified for the engine.
Low oil needs attention
If oil must be added, use a compatible product meeting the vehicle's requirements and investigate repeated oil loss.
Synthetic-blend oil
Blends combine conventional and synthetic base oils, but the finished product still needs to meet the engine's required specifications.
The right oil change starts with the vehicle—not a one-size-fits-all package.
Before choosing engine oil, identify the vehicle's year, make, model and engine and confirm the required viscosity and specifications. A proper oil service also includes the correct filter, correct fill quantity and reset of the maintenance reminder when applicable.
Not sure which oil your car needs?
Joe's Auto Repair serves drivers from 101 University Blvd W in Silver Spring, MD 20901 near Four Corners. We can identify the appropriate engine-oil requirements for your vehicle and help keep its maintenance schedule on track.
Schedule Service →Synthetic and conventional oil questions.
Synthetic oil can offer strong performance under demanding temperatures and operating conditions, but the most important factor is whether the oil meets the viscosity and performance specifications required by your engine.
Check the owner's manual or manufacturer maintenance information for the required viscosity and oil specifications. Requirements can differ by engine and model year even within the same vehicle brand.
Do not substitute an oil that fails to meet the manufacturer's requirements. If the specified oil is synthetic or the required specification is only met by an appropriate synthetic product, use the required oil.
Do not automatically extend the interval simply because synthetic oil is used. Follow the maintenance interval or oil-life system specified by the vehicle manufacturer.
For many vehicles, yes, provided the synthetic oil meets the correct viscosity and all required specifications. Existing leaks or oil consumption should be evaluated separately.
Only if the conventional oil meets every requirement specified for that engine. Some modern vehicles require specifications that should not be replaced with a conventional product simply to reduce cost.
Synthetic oil can be appropriate for many high-mileage engines when it meets the required specifications. Mileage alone does not determine whether synthetic oil can be used.
Joe's Auto Repair provides oil-change and preventive-maintenance services at 101 University Blvd W in Silver Spring, Maryland 20901 near Four Corners.