Viscosity
Graded under SAE J300, for example 5W-30: the number with the "W" is the winter grade, the second number is the high-temperature viscosity.
Maintenance
Maintenance
Regular maintenance means following the manufacturer's schedule, not a set of one-size-fits-all tips. Here we explain what a schedule includes and how to read it; take specific intervals and capacities from your vehicle's manual.
Engine oil
A detailed breakdown is on the archived "Oil change" page.
Performance categories and approvals
API and ACEA categories describe an oil's performance level, while manufacturer approvals confirm it meets the requirements of specific engines.
Change interval
Set by the manufacturer by mileage and time. Severe service conditions usually shorten the interval.
Source SAE J300; vehicle owner's manual
Brake fluid
Why it gets changed
Brake fluid is hygroscopic: it absorbs moisture from the air. That is why it is replaced on schedule even when the level looks fine.
DOT ratings
DOT 3, DOT 4 and DOT 5.1 are glycol-based fluids. DOT 5 is silicone-based and does not mix with glycol fluids. The required rating is in the manual or on the reservoir cap.
What the schedule covers and where to find the values
| Item | Why it needs service | Where to find the interval and spec |
|---|---|---|
| Engine oil and filter | Oil ages and gets contaminated, losing its protective properties | Maintenance schedule, engine oil section of the manual |
| Brake fluid | Absorbs moisture, and its performance degrades | Maintenance schedule; DOT rating in the manual |
| Engine air and cabin air filters | Get clogged, especially in dusty conditions | Maintenance schedule, severe service notes |
| Coolant | Protects against overheating, freezing and corrosion | Manual: coolant type and replacement interval |
| Transmission fluid | Works under different conditions than engine oil | Manual: requirements vary by transmission |
Source Vehicle owner's manual; manufacturers' websites
Key terms
- Maintenance schedule
- The list of services and intervals the manufacturer sets for a specific model and engine.
- Severe service conditions
- Short trips, long idling, dust, towing and other conditions for which the manufacturer may shorten intervals. The exact list is in the manual.
- Manufacturer approval
- Confirmation that an oil or fluid meets a specific automaker's requirements. It is printed on the packaging.
- Hygroscopic
- Able to absorb moisture from the air. The main reason brake fluid needs regular replacement.
Maintenance questions
Can I mix brake fluids with different DOT ratings?
DOT 5 (silicone) must not be mixed with glycol fluids. Whether glycol fluids can be mixed depends on the automaker's and fluid maker's instructions; the safest choice is the rating listed in your manual.
If I don't drive much, can I change the oil less often?
Intervals are usually set by both mileage and time, whichever comes first. Short trips often count as severe service. Check the schedule for your model.
Sources
- Vehicle owner's manual
- SAE J300: engine oil viscosity classification
- API and ACEA classifications
- Automakers' and lubricant manufacturers' websites
This site does not replace your vehicle's owner's manual or maintenance schedule: take service intervals, fluid capacities, torque specs and fluid specifications only from there. Check design and emissions requirements with official sources.