Car parts glossary

The terms that actually matter when you are buying a part, explained in one line each. No jargon, no fluff.

Battery

Cold Cranking Amps (CCA): CCA is the current a battery can deliver for 30 seconds at 0°F while staying above 7.2 volts. Higher CCA means stronger cold-weather starting. It is the most important rating for cold climates. Always match or exceed the CCA your vehicle specifies.
Cranking Amps (CA): CA measures cranking current at 32°F instead of 0°F, so the number is always higher than CCA for the same battery. Sometimes labeled MCA (marine cranking amps). Do not confuse a high CA figure with CCA.
Reserve Capacity (RC): Reserve capacity is how many minutes a fully charged battery can run a 25-amp load before dropping to 10.5 volts. It estimates how long your car can run if the alternator fails.
BCI Group Size: The BCI group size (for example 24F, 35, 47, H6) defines a battery's physical dimensions and terminal layout, not its power. The right group size is the one that fits your tray and connects correctly.
AGM Battery: An AGM (absorbent glass mat) battery holds its acid in fiberglass mats, so it is sealed, spill-proof, and handles deep cycling and stop-start systems better than a flooded battery. Vehicles with stop-start or heavy electronics often require AGM. You can replace a flooded battery with AGM, but not always the reverse.
EFB Battery: An EFB (enhanced flooded battery) is an upgraded flooded design built for entry-level stop-start cars. It sits between a standard flooded battery and AGM.
Flooded Battery: A flooded (wet cell) battery is the traditional lead-acid type with liquid electrolyte. It is the cheapest option and fine for vehicles without stop-start.
Amp Hours (Ah): Amp hours measure a battery's total energy storage: how many amps it can supply over time. A 60 Ah battery can in theory deliver 3 amps for 20 hours.

Oil

Oil Viscosity: Viscosity is an oil's resistance to flow. In a grade like 5W-30, the first number is cold-flow (lower is better when cold) and the second is thickness at engine temperature.
Multigrade Oil: Multigrade oil (for example 5W-30) meets two viscosity standards at once: thin enough to flow on a cold start and thick enough to protect at operating temperature. Almost all modern oils are multigrade.
The W in Oil Grades: The W stands for Winter. The number before it is the oil's cold-weather flow rating, not weight. 0W flows better when cold than 5W.
Synthetic Oil: Synthetic oil is chemically engineered for more consistent molecules than conventional oil, giving better flow, heat resistance, and longer drain intervals. Most new engines require full synthetic.
API Service Rating: The API rating (such as SP or SN) on an oil bottle shows which engine standard it meets. Newer ratings are backward compatible; use the rating your manual specifies or newer.
Oil Capacity: Oil capacity is how much oil the engine holds at an oil-and-filter change, measured in quarts or liters. Using the right amount matters as much as the right grade.
dexos: dexos is a General Motors oil specification. GM vehicles often require a dexos-approved oil to keep the warranty valid; look for the dexos mark on the bottle.

Wipers

Beam Wiper Blade: A beam blade has a single curved spring with no external frame, so it presses evenly and resists ice and snow buildup. It is the most common modern design.
Conventional Wiper Blade: A conventional (bracket) blade uses a metal frame with pivot points. It is cheaper but clogs with snow and wears unevenly compared with a beam blade.
Hybrid Wiper Blade: A hybrid blade wraps a conventional frame in an aerodynamic shell, combining a low profile with frame-style strength.
Wiper Connector Type: The connector is the clip that attaches the blade to the wiper arm (for example J-hook, pinch-tab, bayonet). The blade must match both the size and the connector for your car.

Bulbs

Halogen Bulb: A halogen bulb heats a tungsten filament inside halogen gas. It is the cheapest headlight type, easy to replace, but dimmer and shorter-lived than HID or LED.
HID / Xenon Bulb: An HID (high-intensity discharge), or xenon, bulb creates light with an electric arc in gas. It is brighter and whiter than halogen and needs a ballast to run.
LED Headlight: An LED headlight uses light-emitting diodes for instant, efficient, long-lasting light. Many newer cars use sealed LED units that are not user-replaceable.
Bulb Base Code: A code like H11, 9005, or H7 identifies a bulb's base, wattage, and beam type so it fits the housing. Low beam and high beam often use different codes.

General

Vehicle Fitment: Fitment means whether a part is built to fit a specific year, make, and model. A part that fits one trim or engine may not fit another, so fitment is checked by exact vehicle.
OEM: OEM (original equipment manufacturer) means a part made to the automaker's exact specification, the same as what came on the car from the factory.
Aftermarket Part: An aftermarket part is made by a company other than the automaker. Quality ranges from economy to better-than-OEM; the key is that it meets the correct fitment and specs.
Stop-Start System: Stop-start shuts the engine off at idle to save fuel and restarts it when you move. It puts heavy demand on the battery, so these cars need an AGM or EFB battery, not a standard one.