Hearing terms like “synthetic” or “conventional” motor oil can be confusing if you are not familiar with them. Both of these types of oil lubricate your engine, but they don’t perform or last the same.
So, synthetic vs conventional oil: Which is right for your car?
Full synthetic uses engineered base oils with more uniform molecules for better high/low-temperature stability and deposit control; conventional is refined petroleum suited to lighter, everyday use.
The best choice depends on your vehicle’s required spec (check the owner’s manual: API/ILSAC/ACEA), climate, driving style, and warranty. Listed below, you’ll find a quick guide that breaks down what goes into your engine in a clear, straightforward way.
A Short Note About Synthetic Oil
Synthetic oil is an engineered lubricant. It’s made either by chemically building base oils (e.g., PAO/esters) or by severely refining petroleum (Group III). This results in more uniform molecules that resist breakdown, delivering better deposit control and stability than conventional oil. Also, synthetic oil provides more reliable protection in both extreme heat and cold (assuming the correct grade/spec is used). You can also try a synthetic blend, which mixes synthetic and regular oil.
Benefits of Synthetic Oil:
- Strong wear protection and film strength.
- Better cold-start flow and high-temperature stability.
- Longer service life (follow your oil-life monitor/manual).
- Greater resistance to oxidation, sludge, and deposits.
- Often slightly lower friction, which can help fuel economy.
Drawbacks of Synthetic Oil:
- Higher upfront cost than conventional.
- Not always required for light, everyday use if your manual car allows conventional, and if oil change intervals are followed.
- Use what’s specified: some older/classic engines may need specific formulations (e.g., high-zinc); follow manufacturer guidance.
A Short Note About Conventional Motor Oil
Conventional (mineral) motor oil is made by refining crude petroleum into base oils (typically API Group I/II). It is then blended with an additive package (detergents, dispersants, anti-wear agents, antioxidants, viscosity index improvers). Modern processes such as distillation, hydrotreating, and hydrocracking remove most contaminants. It works well for many engines, but its molecules are less uniform than synthetic ones, so it tends to oxidize and shear faster under severe operating conditions.
Benefits of Conventional Oil
- Lower upfront cost; widely available.
- Adequate protection for many older or lower-stress engines when changed on time.
- A reasonable choice for older engines if the owner’s manual permits it and driving is light/regular.
Drawbacks of Conventional Oil
- Breaks down faster; needs more frequent oil changes.
- Generally less stable in extreme cold/heat than synthetics.
- Higher risk of sludge/varnish under severe use (short trips, high heat, towing) if oil change intervals are stretched.
- Not ideal for many modern/high-performance or turbocharged engines.
Synthetic vs Conventional Oil
Choosing between synthetic and conventional doesn’t have to be tricky. Both oils protect your engine, but they perform differently. Always start with your owner’s manual: it tells you the exact viscosity (e.g., 0W-20, 5W-30) and required standard (API/ILSAC/ACEA or OEM). Also, some engines require synthetic, while others allow any oil (conventional, synthetic, or synthetic blend) as long as it meets the specified grade and spec to keep performance and warranty intact.
What Makes These Oils Different
Conventional oil is refined petroleum with additives; its molecule sizes vary more. Synthetic oil is heavily engineered. It’s either chemically built or severely refined for more uniform molecules and greater stability. Synthetic oil usually handles mechanical stress, high heat, and oxidation better than conventional oil. It is why most modern cars recommend synthetic oil.
Purity & Performance
Synthetic’s uniform structure reduces friction, resists breakdown, and limits sludge or varnish. Conventional oil does the job, but degrades faster under heavy loads, short trips, high heat, or neglected intervals.
How They Handle Hot and Cold Days
If you live where winters are frigid or summers get very hot, synthetic oil is safer. Synthetics flow better at low temperatures, helping with protection on startup. It also maintains viscosity and film strength longer during hot temperatures. Conventional oil thickens in cold weather. It makes the engine work harder during cold starts. In very hot weather, it can break down faster and lose strength. It’s why many newer engines require or recommend synthetic or fully synthetic oil.
Engine Wear & Cleanliness
Engines have many moving parts that rub together, causing wear over time. Synthetic oils typically provide stronger wear protection and better deposit or sludge control than conventional oils. Conventional oil protects adequately when changed on time, but it’s less forgiving if oil change intervals are stretched.
How Often You Need to Change the Oil
Usually, one big reason people choose synthetic oil is the longer time between oil changes. With synthetic, you can often drive much longer before you need an oil change. But conventional engine oil needs to be changed more often. It breaks down faster, so you might have to replace it sooner to keep the engine safe. This is why switching from conventional oil to synthetic oil is common today.
How Much Each Type Costs
Synthetic oil often costs more per change. Sometimes even as high as four times that of conventional oil, but the longer life and protection can offset that over time. Conventional is cheaper upfront but may require more frequent changes.
Fuel Use and the Environment
Synthetic oil’s lower friction and viscosity stability can slightly improve fuel economy. It may also allow longer change intervals, which reduces oil, filters, and packaging waste. Conventional oil typically requires more frequent changes, creating more used oil over time.
So, Which One is Best for Your Car?
Actually, it depends on your car. Check your owner’s manual. Most newer cars require or recommend synthetic oil for proper protection and warranty. Synthetic usually offers better protection and cleanliness, and requires far longer times between oil change intervals. But if your engine allows conventional and your driving is light/normal, conventional can still work. It is only that you need more frequent oil change intervals. Check out this article to know about the signs that your car needs an oil change.
If you don’t want to change the oil yourself or can’t right now, you can call for help. The iTOWu app is a 24/7 roadside assistance service where you can schedule an oil change with certified professionals right from the app.
Last Note
The best answer is to check your owner’s manual. If it requires synthetic, use synthetic. If it gives you a choice, pick what fits your budget and driving as long as it meets the specified viscosity and specifications to protect performance and warranty.
Both oils protect the engine but perform differently. Synthetic typically offers stronger, more extended protection and better performance in extreme weather. Conventional can be fine for everyday driving if you change it on time.
The best choice depends on your car, climate, budget, and driving style. With these points in mind, it’s easier to choose an oil that keeps your engine running smoothly and safely.