Engine oil lubricates, cools, and cleans your engine, and it breaks down over time. Full synthetic lasts far longer than conventional oil, but the correct interval always comes from your owner's manual.
7.5k-10k mi
full synthetic interval
3k-5k mi
conventional interval
📊 Quick Comparison
Oil Type
Typical Interval
Cost
Conventional
3k-5k mi
$35-$75
Synthetic blend
5k-7.5k mi
$50-$90
Full synthetic
7.5k-10k mi
$65-$125
Synthetic vs conventional intervals
Conventional oil is generally changed every 3,000 to 5,000 miles. Full synthetic oil commonly lasts 7,500 to 10,000 miles, and some manufacturers specify up to 15,000 miles.
Many modern engines require synthetic oil, so switching to conventional to save money is often not an option.
Follow the oil life monitor if your car has one
Use the exact viscosity grade listed in the manual (for example 0W-20 or 5W-30)
Severe-service driving
Short trips where the engine never fully warms up, extreme cold or heat, dusty roads, towing, and heavy idling all shorten oil life. Under these conditions, use the shorter 'severe service' interval in your manual, even with synthetic oil.
The one-year rule
Even if you drive very few miles, oil should typically be changed at least once a year. Moisture and combustion byproducts accumulate over time regardless of mileage.
Always change the filter
Replace the oil filter with every oil change. A clogged filter can bypass and circulate unfiltered oil, accelerating engine wear.
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❓ FAQ
Is the old 3,000-mile rule still true?
Not for most cars. That figure dates to older oils and engines. Modern synthetic oils and vehicles commonly go 7,500-10,000 miles. Follow your manual and oil life monitor.
Can I switch from conventional to synthetic?
Yes, switching is safe in most engines and there is no 'seal damage' myth to worry about in modern vehicles. Just use the correct viscosity grade.
What if I barely drive?
Change the oil at least once a year even at low mileage, because moisture and acids build up over time.
Does the oil life monitor replace the manual?
The monitor estimates remaining life based on driving conditions and is a good guide, but confirm the maximum interval and viscosity in your manual.
Should I always change the filter too?
Yes. Replace the oil filter every oil change to keep filtration effective.