Choosing the right oil for your aircraft engine is one of the most important maintenance decisions you’ll make. The wrong oil can accelerate wear, cause corrosion, and lead to expensive engine problems. This comprehensive guide covers everything you need to know about aviation oils in 2025.
Why Aviation Oil Matters
Aircraft engines operate under extreme conditions: high temperatures, varying altitudes, extended idle periods, and demanding performance requirements. Automotive oil isn’t designed for these conditions—aviation oil is specifically formulated to protect air-cooled engines in flight environments.
The consequences of wrong oil selection include:
- Accelerated cylinder and cam wear
- Corrosion during storage periods
- Deposit formation and sludge
- Reduced time between overhauls (TBO)
- Potential engine failure
Getting oil right protects your engine investment—potentially $30,000-$70,000 for a typical GA engine.
Understanding Oil Types
Mineral Oil (Straight Weight)
Mineral oil is refined from petroleum without synthetic additives. It’s primarily used during engine break-in because it allows piston rings to seat properly against cylinder walls.
When to Use:
- First 25-50 hours after new engine or overhaul
- When manufacturer specifies mineral oil break-in
Brands: Phillips 66 X/C, AeroShell Oil 80/100
Ashless Dispersant (AD) Oil
AD oils contain additives that keep contaminants suspended in the oil rather than depositing on engine parts. The “ashless” designation means these additives don’t leave metalite deposits that could cause pre-ignition.
When to Use:
- After break-in is complete
- Normal operation of broken-in engines
- Most common type for GA aircraft
Popular AD Oils: AeroShell W100, Phillips 66 X/C Aviation, Exxon Elite
Multi-Viscosity (Multi-Grade) Oil
Multi-viscosity oils (like 15W-50 or 20W-50) provide better flow at cold temperatures while maintaining protection at operating temperature. They’re increasingly popular for year-round flying.
Advantages:
- Easier cold starts with faster oil circulation
- Reduced wear during warm-up
- Good protection across temperature ranges
Popular Multi-Grades: AeroShell 15W-50, Phillips 66 X/C 20W-50
Semi-Synthetic Oil
Semi-synthetic oils blend petroleum base stocks with synthetic components for enhanced performance. They offer some benefits of full synthetics at lower cost.
Example: AeroShell Oil W 15W-50 (contains synthetic components)
Oil Comparison Chart
| Oil | Type | Grade | Best For | Price/Qt |
|---|---|---|---|---|
| AeroShell W100 | AD | SAE 50 | Warm climates | ~$12 |
| AeroShell W80 | AD | SAE 40 | Cold climates | ~$12 |
| AeroShell 15W-50 | Multi-grade | 15W-50 | Year-round | ~$14 |
| Phillips 66 X/C 20W-50 | Multi-grade | 20W-50 | Year-round | ~$13 |
| Exxon Elite 20W-50 | Semi-synthetic | 20W-50 | Premium protection | ~$16 |
| AeroShell Oil 100 (Mineral) | Mineral | SAE 50 | Break-in only | ~$11 |
Choosing the Right Oil for Your Engine
Continental Engines
Continental recommends ashless dispersant oils for normal operation. For break-in, they specify mineral oil for the first 25 hours or until oil consumption stabilizes.
Continental Recommendations:
- Break-in: AeroShell 80 or 100 (mineral)
- Normal operation: AeroShell W80, W100, or 15W-50
- Cold weather: 15W-50 multi-grade or W80
Lycoming Engines
Lycoming also recommends ashless dispersant oils and requires mineral oil for break-in until oil consumption stabilizes (typically 25-50 hours).
Lycoming Recommendations:
- Break-in: Straight mineral oil (AeroShell 80/100)
- Normal operation: AD oil appropriate for climate
- Multi-grade: Approved for most Lycoming engines
Rotax Engines
Rotax 912/914 series engines require automotive-type synthetic or semi-synthetic oils meeting specific specifications. Do NOT use standard aviation oil in Rotax engines.
Rotax Requirements:
- API SG or higher classification
- 10W-40 or 5W-40 viscosity
- Synthetic or semi-synthetic base
- AeroShell Sport Plus 4 is specifically designed for Rotax
Oil Selection by Climate
Hot Climates (Average >80°F)
Use heavier viscosity oils that maintain protection at high temperatures:
- AeroShell W100 (straight 50 weight)
- Multi-grade 15W-50 or 20W-50
Cold Climates (Average <40°F)
Use lighter viscosity for easier cold starts and faster circulation:
- AeroShell W80 (straight 40 weight)
- Multi-grade 15W-50 (flows better cold than straight weight)
Variable Climates
Multi-grade oils provide the best year-round solution:
- 15W-50 works from below freezing to hot summer days
- Eliminates seasonal oil changes
Oil Change Intervals
Typical oil change intervals for GA aircraft:
| Scenario | Interval |
|---|---|
| Regular flying (2+ hrs/week) | 50 hours or 4 months |
| Infrequent flying | 25 hours or 4 months |
| Filtration system installed | Up to 100 hours (per STC) |
Important: Time limits matter as much as hours. Oil degrades from moisture accumulation and acid formation even when the aircraft isn’t flying. Aircraft that sit for extended periods may need more frequent changes.
Common Oil Questions
Can I mix different brands of aviation oil?
Generally yes, if they’re the same type (both AD, same viscosity). However, mixing is not recommended for optimal performance. Top off with what’s in the engine; change to a different brand during oil changes.
Can I switch from straight weight to multi-grade?
Yes, during an oil change. Most engine manufacturers approve multi-grade oils. Check your POH and engine manufacturer recommendations.
How do I know when to change oil?
Follow the shorter of hours or calendar time. Also change if oil is visibly contaminated or oil analysis shows problems.
Should I use oil analysis?
Oil analysis ($25-35 per sample) provides valuable trend data on engine wear. Recommended for all aircraft owners, especially if buying a used aircraft or monitoring an aging engine.
What about CamGuard or other additives?
CamGuard is an aftermarket additive that provides additional corrosion protection, particularly valuable for aircraft that don’t fly frequently. Many owners and some engine shops recommend it. Add at each oil change per manufacturer instructions.
Storage and Handling
Oil Storage:
- Store in a cool, dry location
- Keep containers sealed until use
- Check expiration dates (typically 4-5 years from manufacture)
- Don’t store outside where temperature varies
Before Adding Oil:
- Verify correct type and grade for your engine
- Check oil container for contamination or damage
- Use clean funnels and containers
- Never mix automotive oil with aviation oil
Our Top Recommendations
Best Overall: AeroShell 15W-50
The most versatile choice for year-round flying. Excellent cold flow, high-temperature protection, and wide approval across engine types. Semi-synthetic formulation provides modern protection.
Best Value: Phillips 66 X/C 20W-50
Quality multi-grade protection at a slightly lower price point than AeroShell. Good choice for budget-conscious owners who want multi-grade benefits.
Best for Warm Climates: AeroShell W100
When temperatures consistently stay above 60°F, straight 50-weight provides excellent protection. Simpler formulation, widely available, proven track record.
Best for Cold Climates: AeroShell W80
Lighter viscosity flows faster in cold conditions, reducing startup wear. Switch to W100 or multi-grade for summer flying.
Best for Break-In: AeroShell Oil 100 (Mineral)
The standard choice for new or overhauled engines. Allows proper ring seating without the additives that can prevent break-in.
Oil Purchasing Tips
Buy in Cases: Purchasing a case (typically 12 quarts) saves money versus individual quarts. A typical oil change uses 8-12 quarts.
Price Comparison: Aircraft Spruce, Sporty’s, and Amazon often have competitive pricing. Compare including shipping.
Check Dates: Ensure oil hasn’t been sitting in inventory for years. Fresh oil is better oil.
As an Amazon Associate, Zulu Parts earns from qualifying purchases. Always verify oil compatibility with your engine manufacturer’s recommendations before purchase.