Why Engine Oil Grade Matters
Engine oil has two jobs: lubricate (reduce metal-on-metal friction) and cool (carry heat away from components the coolant can't reach). The grade determines how the oil behaves at different temperatures — too thin at high temperature leaves bearings vulnerable; too thick at cold start means poor initial lubrication on startup.
Understanding Oil Grade Codes
Single-grade (SAE 30): A fixed viscosity regardless of temperature. Standard for most small 4-stroke petrol engines used in warm climates. SAE 30 is specified for most garden equipment engines operating above 5°C.
Multi-grade (10W-30, 10W-40): Behaves like SAE 10 at cold temperatures (easier cold start, better protection during startup) and like SAE 30 or 40 at operating temperature. Better for equipment used in variable climates or started in cold conditions.
What Grade Does My Engine Need?
| Temperature Range | Recommended Grade |
|---|---|
| Above 10°C (most of year) | SAE 30 |
| All year, variable climate | 10W-30 |
| Cold starts below 0°C | 5W-30 synthetic |
Always check the manual — some premium engines specify a particular grade or prohibit synthetic oil.
Oil Change Intervals
- First change: after 20 hours (break-in change)
- Subsequent changes: every 100 hours of operation or once per year, whichever comes first
- Heavy use (construction, commercial): every 50 hours
- After each extended hot operation in dusty conditions: earlier change
What Happens if You Use the Wrong Oil
Too thin (lower viscosity than specified): Oil film breaks down at high temperature, bearings run metal-on-metal, accelerated wear. In severe cases: engine seizure.
Too thick (higher viscosity than specified): Difficult cold starting, poor oil circulation at startup when wear is highest, possible oil pressure issues in narrow galleries.
Car engine oil in a small engine: Detergent additives in car oil cause foaming in horizontal-shaft engines and can damage some seals. Use oil rated for small engines.
FAQ
Can I use 4-stroke motorcycle oil in my generator engine?
Yes — JASO MA-rated 4-stroke motorcycle oil meets or exceeds most small engine specifications. However, it's often more expensive than dedicated small-engine oil with no performance benefit. Use manufacturer-recommended oil where available.