The Quick Answer
Synthetic oil is engineered for longer intervals and tougher conditions; conventional is cheaper and adequate for older, low-mileage engines. The right choice depends on your car, climate, and how long you keep vehicles.
📊 Side-by-Side Comparison
| Feature | Synthetic Oil | Conventional Oil |
|---|---|---|
| Price per quart | $7-$12 | $3-$6 |
| Oil change interval | 7,500-15,000 mi | 3,000-5,000 mi |
| Cold-start protection | Excellent | Fair |
| High-heat stability | Excellent | Average |
| Engine deposit prevention | Superior | Average |
| Best for | Modern, turbo, high-perf | Older, low-stress engines |
When To Choose Each
✅ Choose Synthetic Oil If…
- Your owner manual specifies synthetic (most cars 2010+ and all turbos)
- You drive in extreme heat, cold, or stop-and-go traffic
- You want fewer oil changes per year
- You tow, haul, or drive performance vehicles
✅ Choose Conventional Oil If…
- You drive an older engine (pre-2000) with high mileage that has always used conventional
- You change oil every 3,000 miles religiously
- Cost per change matters more than interval length
- The manufacturer specifically allows conventional
🏆 Our Verdict
Synthetic Oil vs Conventional Oil
Synthetic wins for nearly every modern car. The longer interval, better protection, and small price difference per mile make it the smarter long-term choice. Stick with conventional only if your manual allows it and you change oil on a tight schedule.
❓ Frequently Asked Questions
Can I switch from conventional to synthetic?
Yes. The old leak myth is busted. Modern synthetics are fully compatible. Just do a normal oil change and start using synthetic.
Does synthetic oil really last 15,000 miles?
Full synthetic in a healthy engine driven mostly on the highway, yes. In stop-and-go traffic or severe service, target 7,500-10,000 miles.
Is synthetic blend worth it?
It is a compromise: about 70% of synthetic protection at 60% of the price. Good middle ground but full synthetic gives more peace of mind.
Will synthetic damage older engines?
No. The myth came from early 1970s synthetics that had seal issues. Modern synthetic is safe in any engine.
Does brand matter?
Less than viscosity grade and API certification. Mobil 1, Castrol Edge, Pennzoil Platinum, and Valvoline Advanced are all excellent.
What if my car calls for synthetic and I used conventional?
Change it as soon as possible. Long term, conventional in a turbo or direct-injection engine can cause coking and bearing wear.