The powertrain: engines, motors and the drivetrain
The powerplant makes the turning force:
- Petrol (gasoline) engine: a spark plug lights a fuel–air mix in each cylinder. Most cars and two-wheelers.
- Diesel engine: air is squeezed so hard it gets hot enough to light the fuel. No spark plugs. Trucks, buses, many SUVs.
- Hybrid: a fuel engine plus an electric motor and battery that share the work.
- Battery electric (EV): only an electric motor and a big battery. No oil changes, but tyres, brakes and coolant still need care.
- Others: CNG and LPG engines (common in Indian taxis), hydrogen fuel cell.
The drivetrain carries the turn to the wheels: clutch or torque converter → gearbox / transmission (manual or automatic) → drive shaft or half-shafts → differential (lets the left and right wheels turn at different speeds on a bend) → wheels. FWD drives the front wheels, RWD the rear, AWD/4WD all four.
Engine parts that need regular service: oil and oil filter, air filter, spark plugs, drive belts, coolant, and (for some engines) the timing belt.
Engine systems and owner checks
- Lubrication: oil pump, oil filter, sump. Oil stops metal parts rubbing. Check the dipstick on level ground with the engine off; the level must be between MIN and MAX. Change oil and filter as the manual says (often every 10,000–15,000 km or once a year).
- Cooling: radiator, water pump, thermostat, hoses, fan and coolant. Never open the radiator cap when the engine is hot: hot coolant can spray out and burn.
- Starting: battery, starter motor, ignition switch. Keep terminals clean and tight; a slow crank or clicking means a weak battery.
- Ignition (petrol engines): coil, spark plugs, engine computer. Worn plugs cause misfires and poor fuel economy.
- Fuel: tank, pump, filter, injectors. Use the fuel grade on the filler flap; never fill a petrol car with diesel.
- Electrical: alternator charges the battery; fuses protect circuits. A multimeter on a resting battery should read about 12.6 V.
- Brakes: pedal, master cylinder, brake fluid, discs/drums, pads/shoes. A squeal, a soft pedal or a pull to one side needs a mechanic.
- Steering and suspension: check for play, uneven tyre wear and fluid leaks.
Service information: manual, codes and warning lights
The owner’s manual gives fluid types and amounts, tyre pressures, bulb types, fuse charts and the service schedule. Other sources: the service book, the maker’s website, workshop manuals and recall notices.
Letters and codes:
- VIN (vehicle identification number): 17 letters and digits that identify the car; the 10th character shows the model year.
- Tyre code 205/55 R16 91V: width 205 mm, sidewall height 55% of width, Radial, 16-inch rim, load index 91 (615 kg), speed rating V (240 km/h).
- Oil grade 5W-30: “W” = winter; 5 is how well it flows cold, 30 how thick it stays hot.
Warning lights: red (oil pressure, engine temperature, brake, charging) = stop safely and switch off; amber (check engine, ABS, tyre pressure) = get it checked soon; green/blue = information.
Product safety: read labels and safety data sheets. Coolant is poisonous but tastes sweet: keep it from children and pets. Battery acid burns skin; wear gloves and eye protection. Dispose of used oil at a collection point.
Tools, care, rust, inspections and seasonal preparation
Owner’s toolkit: jack and wheel brace, tyre pressure gauge, tread depth gauge, jump leads or jump starter, torch, gloves, basic spanners and screwdrivers, a multimeter, warning triangle and first-aid kit. Use the right size spanner, pull rather than push, and never work under a car held only by a jack: use axle stands.
Care: wash with car shampoo (not dish soap, which strips wax). Polish removes a thin layer to clear fine scratches; wax or sealant adds a protective coat. Vacuum the interior, clean glass and use UV protectant on the dashboard.
Rust (corrosion): surface rust on paint chips is easy to sand and touch up; scale rust makes bubbles and flakes and needs grinding and primer; penetrating rust makes holes and needs a panel repair. Road salt and coastal air speed it up. Minor repairs: touch-up paint, scratch removers, replacing wiper blades and bulbs.
Safety inspection: lights, horn, wipers, brakes, steering play, tyres, seat belts, exhaust. Weather: for winter use winter tyres, check coolant strength and the battery, carry a scraper and blanket; for hot weather check coolant, the AC and tyre pressure. Keep a service record: it keeps the warranty valid, catches problems early and raises the resale price.
Roadside emergencies and the law
- Stop safely off the road if you can; switch on hazard lights.
- Get everyone out on the side away from traffic; wear a reflective vest.
- Place the warning triangle well behind the car (often 50–100 m on fast roads).
- If anyone is hurt, call emergency services (112 in India and Europe, 911 in North America). Give first aid only if trained.
- Exchange names, licence, registration and insurance details; take photos; do not argue about blame.
- Report the crash to the police and your insurer as your local law requires.
The law: in most countries you must stop after a crash, help the injured and report it; leaving the scene is a serious offence. You must carry a licence, registration and insurance.
Roadside assistance plans (from insurers, carmakers or auto clubs) send help for flat tyres, dead batteries, lock-outs, fuel delivery and towing.
Maths: fuel economy (L/100 km) = litres ÷ km × 100; km per litre = km ÷ litres; cost per km = total fuel cost ÷ km.
Key formulas and definitions
- Fuel economy (L/100 km) = Fuel used (L) ÷ Distance (km) × 100
- Kilometres per litre = Distance (km) ÷ Fuel used (L)
- Fuel cost = Litres × Price per litre; Cost per km = Fuel cost ÷ Distance
- Tyre code: width (mm) / aspect ratio (%) R rim (inches) load index speed rating
- 1 bar = 100 kPa ≈ 14.5 psi
Worked examples
1. A car uses 35 L of fuel for 500 km. Find its fuel economy in L/100 km and km/L.
35 ÷ 500 × 100 = 7 L/100 km. 500 ÷ 35 ≈ 14.3 km/L.
2. Fuel costs 100 per litre. Using the trip above, find the fuel cost and the cost per km.
Cost = 35 × 100 = 3,500. Per km = 3,500 ÷ 500 = 7 per km.
3. Read the tyre code 195/65 R15 91H.
Width 195 mm; sidewall height = 65% of 195 ≈ 127 mm; radial; fits a 15-inch rim; load index 91; speed rating H (up to 210 km/h).
4. The manual says 2.4 bar. Your gauge reads in kPa. What should it show?
1 bar = 100 kPa, so 2.4 bar = 240 kPa.
5. Oil change every 10,000 km. The last change was at 47,500 km. At what reading is the next due?
47,500 + 10,000 = 57,500 km.
6. Car A: 6 L/100 km. Car B: 9 L/100 km. You drive 12,000 km a year and fuel costs 100 per litre. How much does Car A save per year?
A: 12,000 × 6 ÷ 100 = 720 L → 72,000. B: 1,080 L → 108,000. Saving = 36,000 a year.
Common mistakes
- Opening the radiator cap on a hot engine. Wait until it is cold; hot coolant can burn badly.
- Checking tyre pressure after a long drive. Warm tyres read high; check them cold.
- Ignoring an amber light for months, or driving on with a red oil-pressure light. Red means stop safely now.
- Thinking a bigger L/100 km number is better. Lower L/100 km means less fuel used.