Key Facts: Car Care & Automotive Accessories
This page is Garage Lab's maintained fact reference — the spec and standard facts our guides are built on, restated in plain prose. We report buying-guide and specification facts, never repair or safety instructions — always follow your vehicle's owner's manual for maintenance procedures.
Jump starters: peak amps, mAh, and Wh
A jump starter's advertised "peak amp" figure is a manufacturer marketing rating — a brief-burst number, not standardized across brands and not the same measurement as a battery's Cold Cranking Amps (CCA). Sizing a jump starter to your engine is better done from the maker's own engine-displacement chart and independent reviews than by comparing peak-amp claims between brands. Separately, mAh (milliamp-hours) only means something at a stated voltage — Wh (watt-hours, V x Ah) is the actual comparable energy-capacity unit across different packs. Full breakdowns: What Peak Amps Do I Need? and mAh vs Wh on Jump Starters.
OBD2 scanner tiers and protocols
OBD2 tools split into tiers: basic code readers handle generic engine (powertrain) codes only; live-data tools add real-time sensor graphing but stay engine-only; and full-system or bi-directional scanners can reach ABS, SRS/airbag, and transmission modules — but only for vehicles specifically listed in that tool's coverage database. Under the hood, OBD2-era vehicles use one of five recognized protocols (SAE J1850 PWM, SAE J1850 VPW, ISO 9141-2, ISO 14230-4/KWP2000, or ISO 15765-4/CAN, standard since 2008). More in Which OBD2 Scanner Reads ABS Codes? and the full table at The Car Gear Numbers.
Motor oil: SAE grade and API category
In a grade like 5W-30, the number before the "W" (Winter) is the cold-flow viscosity rating — lower flows easier when cold — and the number after the dash is viscosity at normal operating temperature. Neither number is a brand or quality claim by itself. The API service category (SP is the current gasoline-engine tier as of this writing; diesel engines use a separate category like CK-4) covers wear and additive performance standards. Always use the exact SAE grade and API/ILSAC category your owner's manual specifies. See What Does 5W-30 Actually Mean?.
Wiper blade sizing and format
The correct way to find your wiper size is your owner's manual or a manufacturer/retailer year-make-model lookup — not measuring the old blade, which may already be the wrong size. Front driver and passenger blades are frequently different lengths from each other. Beam blades (frameless, single flexing spine) resist ice-jamming better than jointed conventional frames; hybrid blades add an aerodynamic housing over a beam spine. See How to Find My Wiper Size.
Tire pressure gauges and TPMS
Digital gauges commonly claim around ±1 PSI accuracy; dial gauges built to the ANSI B40.1 standard carry a named accuracy grade; pencil-style slide gauges are generally considered least precise. TPMS (built into the vehicle since a phased 2007–2008 US mandate under FMVSS 138) only guarantees a dashboard warning once a tire is meaningfully underinflated — it is an alert system, not a precise routine PSI readout, so a handheld gauge is still the tool for checking exact pressure against your door-jamb placard. See Are Digital Tire Gauges More Accurate?.
Floor mat fitment
Universal mats use a generic trim-to-fit shape; custom ("laser-fit") mats are digitized scans of one specific year/make/model/trim's floor pan and typically lock into factory anchor points. The most common fitment complaint on custom mats is ordering the wrong trim level. See Custom vs Universal Floor Mats.
Battery group size and CCA
A battery's BCI group size (e.g., Group 35, 24F, 65/H6) describes only physical case dimensions and terminal layout — not power. CCA (Cold Cranking Amps) is the separate power spec: amps delivered at 0°F for 30 seconds while holding at least 7.2 volts. Two batteries in the same group size can carry very different CCA ratings, so match both. See What CCA Does My Battery Need?.
Tire tread depth and the penny test
2/32 of an inch is the widely-adopted US legal minimum tread depth for passenger tires, marked by molded wear-bar indicators. The penny test (Lincoln's head down) shows whether more than 2/32 in remains. That legal minimum is a floor, not a safety recommendation — wet stopping distance is measurably worse well before that point, and roughly 4/32 in is often cited as a more realistic real-world replacement mark.
How these facts are maintained
These facts are drawn from SAE, API, ANSI, ISO, BCI, and NHTSA/FMVSS public standards and guidance, plus manufacturer specification sheets, reviewed against our guides and updated on the date shown above when standards or the market change. We do not publish prices or star ratings, every pick names an honest drawback, and we stick to buying-guide and spec framing — never repair or safety procedures. Our full methodology is at How We Evaluate Car Gear.