In BMW model names, "i" stands for fuel injection (petrol/gasoline engine) and "s" stands for sport. A model like "318is" means a 3 Series with a 1.8-liter fuel-injected petrol engine with sport options fitted[1]. But there's a twist: BMW announced in 2024 that it's dropping the "i" suffix from gas-powered cars entirely—going forward, only electric vehicles will carry the "i" designation as a prefix (like the i4 or i7)[2].
The lowercase "i" at the end of BMW model names dates back to the late 1960s with models like the 2000tii[3]. At that time, fuel injection was genuinely innovative technology—most cars used carburetors.
BMW used "i" to differentiate between their fuel-injected and carbureted models. A "325i" had fuel injection; a standard "325" did not[4]. When fuel injection became universal across BMW's lineup in the 1980s, the "i" designation stuck anyway as a tradition.
The "i" simply means the engine runs on gasoline (petrol) and uses electronic fuel injection[5]. Diesel BMWs use "d" instead—so "320d" indicates a 3 Series with a diesel engine.
The lowercase "s" historically signifies a sport variant. Models like "318is" or "Z4 3.0si" had the sport package or higher-performance tuning compared to standard versions[1].
You'll also see "s" combined with other letters:
The most recent use of "ti" appears on the BMW 128ti, a hot hatch competing with the Volkswagen Golf GTI.
BMW's naming convention follows a logical structure once you understand it[5]:
| Letter | Position | Meaning | Example |
|---|---|---|---|
| i | End (suffix) | Fuel injection (gasoline) | 330i |
| d | End (suffix) | Diesel engine | 320d |
| e | End (suffix) | Plug-in hybrid (PHEV) | 745e |
| L | End (suffix) | Long wheelbase | 760Li |
| i | Start (prefix) | All-electric (BMW i brand) | i4, i7 |
| M | Start or middle | BMW M performance | M3, M340i |
| X | Start (prefix) | SUV/crossover | X3, X5 |
| Z | Start (prefix) | Roadster | Z4 |
The first digit indicates the series size (1-8, larger numbers = larger cars). The following digits historically referenced engine displacement but now indicate relative performance level[5].
Here's where confusion enters. When "i" appears at the beginning of a BMW model name, it represents something completely different—BMW's electric vehicle sub-brand launched in 2011[6].
| Position | Meaning | Examples |
|---|---|---|
| Suffix (end) | Fuel injection | 330i, M440i |
| Prefix (start) | Electric vehicle | i4, i7, iX |
In this context, "i" stands for "innovation" according to BMW[7]. The BMW i brand was conceived to represent the company's commitment to electric mobility and sustainability. Current BMW i models include:
Electric SUVs add an "X" between the "i" and series number (iX1, iX3, iX)[9].
In 2024, BMW confirmed a major change: the "i" suffix will disappear from all gas-powered models[2]. Going forward, only electric vehicles will carry the "i" designation.
"We would like to keep 'i' as an asset, and we would like to keep it as a signature to indicate you're driving an electric car," explained Bernd Körber, BMW's senior vice president of brand and product management[3].
The transition began with the 2025 BMW X3 M50, which replaced the X3 M40i—notice the dropped "i"[2]. The new BMW 1 Series and 2 Series Gran Coupe also adopted this naming change by end of 2024[10].
This means future gas BMW model names will simply end in numbers:
The reason? Customer confusion. When BMW sells both a 440i (gas) and an i4 (electric), the lowercase "i" appearing in different positions creates unnecessary complexity[11].
Beyond "i" and "s," BMW uses several other identifiers[5]:
| Code | Meaning |
|---|---|
| xDrive | All-wheel drive (most models) |
| sDrive | Rear-wheel or front-wheel drive (X and Z models) |
| Badge | Meaning |
|---|---|
| M | Full BMW Motorsport model (M3, M5, X5 M) |
| M Performance | Enhanced but not full M (M340i, M50) |
| Competition | Track-focused M variant |
| Code | Meaning |
|---|---|
| GT | Gran Turismo (hatchback) |
| Gran Coupe | Four-door coupe |
Understanding these codes helps decode any BMW. A "540i xDrive M Sport" tells you: 5 Series, 40-level performance, gasoline engine, all-wheel drive, with the M Sport package. (Though remember—new 5 Series models will drop that "i" going forward.)
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