---
name: "car_maintenance"
description: "Car maintenance for non-mechanics: oil change intervals, tire pressure and tread checks, brake wear signs, fluid top-ups, and what every dashboard warning light means. Triggers when someone asks about car upkeep, a dashboard light came on, brakes are making noise, tire pressure or tread depth, oil change timing, or 'what does this car warning light mean', e.g. 'my check engine light is on', 'how often should I rotate my tires', 'my brakes are squeaking'."
metadata: { "includeInPrompt": true }
---

# Car Maintenance

## Purpose
Give people who are not mechanics enough knowledge to keep a car safe and healthy: the
cheap, easy checks they can do themselves, what the dashboard lights actually mean, and
when a noise or light means "fix it this week" versus "pull over right now." Every interval
and threshold below is a typical range from service sources; the owner's manual always wins
for a specific vehicle.

## Workflow

### 1. The monthly five-minute check
Walk the car through this once a month and before long trips. Cold engine, car parked level.
1. **Tires** - pressure gauge on each valve, compare to the spec on the driver's door jamb
   (NOT the max pressure printed on the tire sidewall). Also glance at tread and sidewalls
   for bulges, cuts, or nails.
2. **Engine oil** - pull the dipstick, wipe it, reinsert fully, pull again. Level should sit
   between the min and max marks. If it is at or below min, add the correct oil type (from
   the manual or the oil cap), do not just drive on low oil.
3. **Coolant** - look at the translucent overflow reservoir, level between min/max marks.
   Never open the radiator cap while the engine is hot.
4. **Washer fluid** - top up with the right seasonal formula.
5. **Lights** - headlights, brake lights, turn signals, hazards. A burnt brake-light bulb is
   a ticket waiting to happen.

### 2. Answering "when do I change my oil?"
Intervals by oil type (see references/maintenance_intervals.md for the full table):
- Conventional: every 3,000 to 5,000 miles
- Synthetic blend: every 5,000 to 7,500 miles
- Full synthetic: every 7,500 to 15,000 miles (most manufacturers say 5,000 to 10,000)

The 3,000-mile rule is a holdover from the era of crude engines and crude oil; on modern
full synthetic it wastes money. The two reliable guides are the owner's manual and the
car's oil-life monitor. Changing oil late or running low is one of the fastest ways to
kill an engine, so this is the one interval never to stretch past the manual's limit.

### 3. Answering tire questions
- **Tread depth:** legal minimum is 2/32 inch, but wet traction drops off well before that.
  Replace at or below 2/32; start planning the replacement around 4/32 if the driver faces
  rain or winter.
- **The penny test:** put a penny upside down (Lincoln's head first) in a tread groove. If
  you can see the top of his head, tread is at or below 2/32 inch, replace the tire.
  A quarter covers down to 4/32 inch (if Washington's head is covered, you have 4/32+ left).
- **Wear bars:** raised rubber bars molded across the grooves at 2/32 inch. When tread is
  flush with them, the tire is done.
- **Rotation:** every 5,000 to 7,500 miles so all four wear evenly (fronts wear faster on
  most cars). Rotation is also when a shop can spot alignment problems early.
- **Pressure:** check monthly on cold tires (driving heats tires and reads high). Under-inflated
  tires handle badly and burn more fuel; over-inflated ones wear unevenly and grip less.
- **Age:** a tire over 6 years old should be replaced even if the tread looks fine (check the
  DOT date code on the sidewall).

### 4. Answering brake questions
Brake pads are consumables; they last roughly 25,000 to 65,000 miles. Highway drivers get
more, city stop-and-go drivers get less, and fronts wear faster than rears.
- **Squeal when braking** - a small metal wear indicator is exposed as the pad wears down.
  High-pitched squeal means the pads are nearly gone. Book a brake job this week.
- **Grinding** - the pad material is gone and metal is scraping the rotor. This damages the
  rotors and turns a pad job into a pads-plus-rotors job. Stop driving it as much as
  possible and get it in immediately.
- **Vibration in the pedal or steering wheel** - often a warped rotor; get it inspected.
- **Pedal feels spongy or sinks** - air or moisture in the lines, or a fluid leak. This is a
  safety issue, not a "next week" issue.
- **Brake fluid** absorbs moisture over time, which lowers its boiling point. Most makers
  call for replacement every 2 to 3 years or 30,000 to 45,000 miles. Dark or cloudy fluid
  in the reservoir is a sign it is overdue.
- A slight squeak on the first stop of a damp morning that disappears after a few uses is
  usually just surface rust on the rotors, not a worn pad.

### 5. Answering "what does this dashboard light mean?"
Color is the first signal. The full decoder lives in references/dashboard_lights.md; the
rule of thumb:
- **Red light = stop now.** Oil pressure (engine damage in minutes if it keeps running),
  coolant temperature (overheating, pull over, shut off, wait 30 to 60 minutes before
  touching the cap), brake system warning (possible brake fault), battery/charging (the
  alternator is not charging; the car will stall and may not restart).
- **Amber light = check soon.** Steady check engine (a fault is logged; schedule a scan
  this week), TPMS (a tire is low, check pressures, then look for a leak), ABS/stability
  (safety system needs inspection), airbag fault (needs a professional).
- **Flashing check engine = stop driving.** A flashing light usually means an active
  misfire that can wreck the catalytic converter. This is the exception to "amber means soon."
- **Green/blue = information only.** Headlights on, high beams, cruise control, fog lights.

### 6. The fluids cheat sheet
- **Coolant (antifreeze):** keeps the engine at operating temperature; 50/50 coolant-water
  mix in most cars. Exchange interval varies widely, roughly 30,000 to 100,000 miles
  depending on the coolant type. Low coolant with no visible leak is a reason to see a
  mechanic (it goes somewhere).
- **Transmission fluid:** automatic 60,000 to 100,000 miles; manual 30,000 to 60,000;
  CVT 30,000 to 50,000. Some cars have sealed units the owner cannot check, a dealer
  handles those. Healthy ATF is pink/red; brown/black or burnt-smelling means overdue.
- **Power steering fluid:** many new cars use electric steering and have none; if yours
  has a reservoir, keep it topped to the line.
- **Washer fluid:** the one fluid with no interval. Keep it full; swap to winter formula
  before freezing weather.

### 7. Keeping a maintenance log
Every car should have a simple running log: date, mileage, what was done. It makes
diagnosing problems ("the vibration started after the rotation") and resale (buyers trust
documented cars) much easier. The template in assets/maintenance_log.md is a good starting
point; the skill can generate one for the user and keep entries dated in plain language.

## Output Contract
For a specific question: a direct answer first (what to do, how urgent), then the how-to
steps, then what to watch for next. Never lead with theory. For a general request ("teach
me car maintenance" or "help me keep my car healthy"), deliver: the monthly check, the
interval table for their car type if known, the dashboard light decoder, and a maintenance
log template. Keep numbers as ranges and name the owner's manual as the tiebreaker.

## Operating Rules
1. **Never invent numbers.** Every mileage, depth, pressure, and time figure in this skill
   was verified against service sources. If asked about a figure not covered here, say so
   and point at the owner's manual, never guess.
2. **Safety-first ordering.** Anything involving brakes, steering, or a red dashboard light
   gets the urgent callout before the explanation.
3. **DIY boundary.** Topping up oil, coolant (cold engine), washer fluid, and tire pressure
   are owner-safe. Brake pads, rotors, fluid flushes, transmission service, and anything
   under the car go to a mechanic. Never walk a non-mechanic through brake disassembly.
4. **Do not diagnose specific faults.** Offer likely causes with the caveat that a scan or
   a mechanic's eyes confirm it. A check engine light has hundreds of possible codes;
   do not name one as the answer without a code read.
5. **No brand loyalty.** Do not recommend specific oil brands, tire brands, or shops unless
   the user asks for recommendations, and then frame it as one option among several.
6. **Keep the car identifiable.** When known, tailor intervals and fluids to the actual
   year, make, and model. When unknown, say which parts of the advice vary by vehicle.