Vehicle Fluid & Maintenance Guide
Common vehicle fluids — type, change interval, symptoms of low / contaminated.
Reference
Always check the owner's manual for your specific vehicle — these are general guidelines.
Vehicle fluids
| Fluid | Type | Typical interval | Notes |
|---|---|---|---|
| Engine oil | Conventional / synthetic blend / full synthetic | 3 000 – 10 000 mi | Match viscosity grade (5W-30 etc.) |
| Transmission (auto) | ATF (Dexron, Mercon, or Toyota WS, etc.) | 30 000 – 100 000 mi | Many "lifetime" fluids benefit from change ~60k |
| Transmission (manual) | Gear oil (GL-4 or GL-5) | 30 000 – 60 000 mi | GL-5 can attack brass synchros |
| Coolant / antifreeze | IAT (green), OAT (orange/pink), HOAT | 30 000 – 150 000 mi | Don't mix formulations |
| Brake fluid | DOT 3, DOT 4, DOT 5.1 (glycol) | Every 2–3 years | Absorbs moisture; boiling point drops over time |
| Brake fluid (DOT 5) | Silicone | Not hygroscopic | Never mix with glycol-based fluids |
| Power steering | PSF / ATF per manual | 50 000 mi or with leak | Some use regular ATF, some specific PSF |
| Differential / gear oil | GL-5 gear oil | 30 000 – 50 000 mi | LSD may need special friction modifier |
| Transfer case | ATF or gear oil per manual | 30 000 – 60 000 mi | |
| Washer fluid | Methanol / ethanol | Refill as needed | Winter mix resists freezing |
| AC refrigerant | R-134a (pre-2017), R-1234yf (2017+) | Only on leak repair | Do not mix types |
Notes
- Dark / burnt oil smell in ATF usually means torque converter or clutch wear.
- Milky engine oil on the dipstick indicates coolant intrusion — possibly a head gasket failure.
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