MyCarWhy
Car questions, answered in plain English
Symptoms, maintenance, buying, and paperwork — sorted into the next useful check before you guess.
MyCarWhy is a free English site for US drivers. Zeng Feng (MyCarWhy Editorial) maintains it: symptom triage when the car acts up, buying and ownership guides, and tool buyer guides. About the site.
Guides
When the car acts up
Pick the area of the car that matches the symptom, or jump straight to a guide below. Each one opens with what the clue usually means, then the checks that sort look-alike causes.
Car shakes when brakingSort trembling or shaking by braking, acceleration, speed, idle, snow, or a flashing engine light.
Why does my car smell like gasSort a raw-fuel smell by the cabin, the filler, and whether you can see liquid.
Why does my car smell like rotten eggsSort a sulfur smell by the tailpipe, the fuel, and a hot battery.
How long does a car battery lastSort a slow crank by age, heat, short trips, and the charging system.
Engine repairSort an engine job by an oil leak, a head gasket, the computer, or a cracked block.
Car noisesSort a buzz, rattle, click, whine, hum, grind, or hiss by when it starts.
Rough idleSort mounts from vacuum leaks and misfires with a Neutral test, scan order, and when not to buy a tune-up kit.
Car ac repairSort warm vents by no airflow, a refrigerant leak, or a recharge that did not last.
How to open a car door lockedSort a door that will not open by keys left inside, no key, a dead latch, or a dead lock.
Why my car won't startSort a no-start by click, crank, silence, fuel, or a locked brake interlock.
Why would my car lose power while drivingSort a power drop by limp mode, fuel, air, spark, or a clogged exhaust.
Why is my battery light on in my carSort a battery lamp by charging fault, belt, cables, and when to tow.
Why does my car say engine power reducedSort a reduced-power message by scan, throttle faults, voltage, and when to tow.
Why is my car ac blowing warm airSort warm vents by no air, a leak, a blend door, or a musty evaporator.
Why do cars need oil changesSort dark oil, short trips, oil lights, and overdue intervals before wear spreads.
How to change car air filterSort engine vs cabin, read the interval, seat the element, and know when DIY should stop.
How to check car fluidsSort oil, coolant, brake, transmission, and washer checks, plus how do you put coolant in a car before a low level becomes a tow.
How to stop car from fogging upSort inside fog from outside fog, set defrost with A/C, and find filter or leak causes.
How to prevent rust on a classic carSort salt, garage humidity, door drains, and cavity wax before rust reaches structure.
How to remove a tint from a car windowSort film from factory glass, steam peel side and rear panes, and protect the defroster.
What does the exclamation mark mean on a carSort a dashboard exclamation mark by horseshoe, circle, or triangle before you add air or stop.
Why is my car overheatingSort a climbing gauge by idle vs highway, sudden heat, and a full coolant bottle that still runs hot.
How do you open a car bonnetSort the cabin release, the safety catch, a stuck latch, and when a powered frunk needs 12-volt help.
What is a transfer case on a carSort whether your truck has one, when 4WD is safe on pavement, fluid service, and when to tow.
When to switch to winter tiresUse the ~45°F / 7°C rule, set cold tire pressure after the first snap, and know when studded bans apply.
Prius hybrid batterySort a Prius hybrid battery by READY, P0A80, and the 12-volt auxiliary battery before you pay for a pack.
Power steering fluidMatch ATF or a dedicated fluid to the cap, then sort a turn whine, a hard wheel, and cars with no fluid.
Cold weather car batteryTest before a hard freeze, then choose a jump, a replacement, or a trunk kit with a portable jump starter.
Portable tire inflatorChoose a 12V trunk pump or a cordless inflator, check placard pressure first, and keep repair kits separate.
Buying, title & care
Paperwork, insurance basics, buying decisions, and cabin care — sorted the same way as a symptom: what you are deciding, then the next useful step. View all buying, title & care guides.
Best portable car battery jump starterSort a no-start first, then compare GB20, GB40, and GB70 by engine size.
Best check engine light scannerSort the lamp first, then compare BlueDriver, BD200, and AD310 by job.
Best car battery testerSort slow crank vs charging fault, then compare ANCEL BA101 and TOPDON BT100.
Best fuel injector cleanerSort deposit hesitation vs real injector failure, then compare Sea Foam, Techron, and Red Line SI-1.
Best Bluetooth OBD2 scannerSort phone-app wireless vs handheld, then compare BlueDriver, FIXD, and OBDLink CX.
Best octane boosterSort low-octane ping vs carbon knock, then compare Lucas, STP, and Royal Purple Max-Boost.
Best portable car battery chargerSort maintainer vs jump starter, then compare NOCO Genius1, Genius2, and Battery Tender Plus.
Best code reader for carsSort plug-in handheld vs Bluetooth, then compare Autel AL319, Innova 5210, and ANCEL AD310.
How to prevent Kia Hyundai theftConfirm the free software by VIN, then sort a wheel lock, an OBD port lock, and a parking dash cam.
Fiat Ducato recallMatch the July 2026 fuel-damper campaign by VIN, then decide if a van check-engine scanner is even the right buy.
Best dash camSort front-only vs multi-channel and parking power, then compare Garmin, Nextbase, and Vantrue.
Best car vacuumsSort cordless handheld vs shop vac jobs, then compare BLACK+DECKER and Fanttik picks.
Best cabin air filterSort activated carbon vs HEPA by smell, dust, or allergy, then match EPAuto, Puroma, or Bosch to your car.
Best jumper cablesSort two-car cables vs jump starter, then compare 4-gauge and 2-gauge 20 ft sets.
What to do after a car accident not your faultSort the next step by injuries, a denial, no insurance, a driver who left, or a disputed claim.
What does a car accident lawyer doSort investigation, insurer talks, contingency fees, low limits, and when a claim needs counsel.
Why do people register cars in MontanaSort Montana plates by no sales tax, LLC titles, home-state use tax, and real residency.
Why are red cars more expensive to insureSort a high quote by trim, ZIP, mileage, and coverage—not paint color.
Why is car insurance requiredSort the mandate by state liability rules, lender full coverage, and New Hampshire’s exception.
How to get rid of ants in carSort parking trails from cabin crumbs, clean and bait safely, and know when wiring needs a pro.
How to clean throw up out of carSort roadside containment from enzyme cleaning, dry foam fully, and know when vents need a pro.
How to freshen car interiorSort smell source from fragrance, vacuum and dry mats, fix musty vents, then scent last.
How to clean car windowsSort inside film from outside road film and water spots, use two towels, and know when DIY should stop.
How big is a 2 car garageSort standard 24x24 sizes, square footage, door openings, and clearance for SUVs and trucks.
How long does it take to buy a carSort dealership hours from the full shopping journey, new vs used, F&I, and same-day drive-home.
How long does it take to wrap a carSort bay days from project weeks, full vs partial wraps, prep, cure, and rental planning.
What do I need to register my car in MissouriSort Form 108, title assignment, insurance, property tax proof, inspections, and the 30-day penalty.
What is good mileage for a used carSort annual miles, age, maintenance records, and inspection before you trust the odometer.
What happens if you total a leased carSort the insurance check, the lease payoff, GAP, and which payments still continue.
What is a branded title on a carSort salvage, rebuilt, flood, and lemon brands from a clean title before you buy, insure, or finance.
What happens when your car is totaled but still drivableSort total-loss math, owner-retained salvage, salvage titles, and when a running car is still legal to drive.
What is a lien on a carSort title liens, payoff and release paperwork, and how a lien sale differs from a private sale.
How long does a car inspection takeSort bay minutes from wait time, safety vs emissions, NY and PA clocks, and the fail-and-return loop.
How long does it take to align a carSort rack minutes from wait time, two- vs four-wheel, worn parts, same-day tires, and ADAS.
How to donate a carSort sell vs charity gift, title and liens, tax receipts, non-running pickups, and recipient applications.
Best portable EV charger (Level 2 J1772 EVSE)Sort portable EV charger / portable EVSE kits—J1772 Level 2 vs Level 1—by outlet and amps, then match AIMILER or Lectron.
EV 12V batterySort a dark EV with a full pack as a 12V auxiliary failure, then pick a lead-acid jump pack and a 12V-only tester.
BMW home chargingSort the included BMW portable charger, Wallbox or Wallbox Plus, and when a CCS-to-NACS adapter is the add-on.
Truck bed organizerMeasure the bed, then choose a modular organizer, a tonneau cover, or loose totes for weather and cargo.
Used EV battery healthDemand a VIN-matched battery report before you buy, and skip handheld 12V testers for the traction pack.
EV charging cableSort the included cord from a J1772 extension and the right AC or DC adapter without buying a wallbox by mistake.
VIN recall checkRun the free NHTSA VIN lookup, know what it covers, and sort open recalls from a check-engine light.
How these guides work
Every guide starts by sorting the situation — what you hear, smell, see on the dash, or need to decide — before it names a part or a form. The library below has 71 published guides, including symptom checks across 8 part areas plus buying, title, and care questions.
That same split is how technicians road-test complaints, and it matches what national repair advice already tells drivers in plain language.
“Feeling a vibration on the pedal when you apply the brakes indicates warped brake rotors.”
Cost and interval numbers belong next to that kind of source, not as guesses. AAA puts pads and rotors at about $250–$500 per axle on average, and brake pads lasting about 30,000–80,000 miles depending on use. On oil, AAA's maintenance myths piece reports that 45% of people still believe in a 3,000-mile oil change, while most cars 15 years or newer fall in a 5,000–7,500 mile band — always subject to the owner's manual.
