Conventional oil uses base oils refined from crude oil. Synthetic oils use base oils that are chemically engineered for more uniform molecules. Synthetic-blend oils mix the two. All of them contain additive packages for detergency, wear protection and more. Whatever you choose, the oil must meet the viscosity and specification in your owner’s manual.
Where the differences show up
- Cold starts: synthetic base oils generally flow better in the cold, which matters on frigid mornings.
- Heat: synthetic base oils generally resist oxidation and thickening at high temperatures.
- Volatility: lower-volatility oils lose less to evaporation, which can mean fewer top-offs.
- Drain intervals: some synthetic oils are formulated for longer intervals; the product label and your warranty terms tell you what applies.
Common questions people have
Switching to synthetic does not require a special flush, and conventional and synthetic oils are compatible. Older engines with existing leaks may show them regardless of the oil type; oils made for high-mileage engines include seal conditioners.
How to choose
- Start with the manual: required viscosity and specification come first.
- Consider your climate: very cold starts or very hot operation favor oils built for those extremes.
- Consider how you drive: towing, plowing, short trips and idling are severe service.
- Decide on the interval you want, within the manufacturer’s warranty requirements.
- Consider engine age: high-mileage formulas are designed for older engines.
- Use the lookup to see which AMSOIL oils are listed for your vehicle.
- Keep records of each oil change.
Frequently asked questions
Can I switch from conventional to synthetic?
Yes. They are compatible, and no special flush is needed. Use the viscosity and specification in your manual.
Can I go back to conventional after using synthetic?
Yes. Switching back and forth does not harm an engine.
Will synthetic oil cause leaks in an older engine?
Synthetic oil does not cause leaks. An engine with worn seals may already be leaking or about to leak; high-mileage formulas include seal conditioners.
AMSOIL products for this job
- AMSOIL Signature Series 100% Synthetic Motor Oil. AMSOIL says: “Protects – Ultimate long-life anti-wear protection”; “Cleans – Fights sludge and carbon buildup”.
- AMSOIL 100% Synthetic High-Mileage Motor Oil. AMSOIL says: “Unique chemistry for vehicles with over 75,000 miles”; “Enhanced anti-wear additives”.
- AMSOIL Synthetic-Blend Motor Oil. AMSOIL says: “API & ILSAC licensed”; “Helps reduce oil consumption”.
AMSOIL footnotes the Signature Series “Cleans” claim as “Based on Sequence VH and IIIH tests.”
Product wording above is quoted or summarized from amsoil.com. Read each product’s label and data sheet for directions.
Use AMSOIL’s official lookup guide to see what is listed for your vehicle or equipment, then order online whenever it suits you.