Engine Codes Explained: What the Letters and Numbers Mean

The letters and numbers associated with an engine do not follow one universal decoding system. A label such as 2.0L I4 Turbo describes basic specifications, while a code such as an engine-family identifier is defined by the manufacturer. A stamped engine serial number, a casting number and the engine character inside a VIN are different identifiers and should not be decoded with the same chart.

Five kinds of engine numbers people commonly mix up

What common specification abbreviations mean

• 2.0L: approximately 2.0 liters of total cylinder displacement.
• 1998 cc: the same type of displacement measurement expressed in cubic centimeters.
• I4 or L4: an inline four-cylinder layout.
• V6 or V8: six or eight cylinders arranged in two banks forming a V.
• T or Turbo: often indicates turbocharging in a specification label, but a letter inside a manufacturer engine code may mean something else.
• DI, GDI or similar: often refers to direct fuel injection, although manufacturers use their own trademarked terms.
• HP, PS or kW: power units, not engine displacement or engine identification numbers.

These descriptions are useful when they appear in a specification sheet. They should not be used to invent a meaning for every character stamped on an engine block.

Why a single letter does not have a fixed meaning

The old version of this page claimed that letters such as A, N, O or S had universal meanings. They do not. One manufacturer may use a character for an engine family, another for a market or emissions version, and another may not use that character at all. Even codes from the same company can change between generations.

Perkins, for example, publishes its own nomenclature showing how characters can represent family, cylinder count, emissions level, aspiration and rating. That system is useful for Perkins engines, not as a master key for Ford, Volkswagen, BMW, Honda or Toyota codes.

Is the engine code the same as the engine number?

Not necessarily. The engine code usually identifies a design or family shared by many engines. The serial number identifies an individual unit. The stamped location also varies. Ford owner manuals show different engine-number locations depending on engine and vehicle, which is why an image from another model can send you to the wrong part of the block.

Can the VIN identify the engine?

Usually it can identify an engine type, but the popular rule that “the eighth digit is always the engine” is not universal across every vehicle and market. U.S. VINs contain manufacturer-coded specification data, and the details vary by manufacturer. NHTSA’s vPIC decoder uses manufacturer-supplied data to decode the full VIN and can return an engine model, displacement, cylinder count and other available fields.

Use the full 17-character VIN and model year in the NHTSA VIN decoder. If the result is incomplete, confirm it with the manufacturer or a dealer parts department rather than guessing from one character.

How to identify an unknown engine correctly

1. Record the full VIN and model year.
2. Photograph the under-hood emissions label and any engine-information label.
3. Find the stamped engine number or code using the correct owner’s or workshop manual.
4. Keep casting numbers separate from the complete-engine identifier.
5. Give the VIN, engine code and photographs to the parts supplier before ordering internal engine parts.
6. For a replacement engine, verify both the original vehicle specification and the code on the installed engine; they may no longer match.

What should you search for?

Search the exact manufacturer, model, year and the complete code, including spaces, hyphens and suffixes. A query such as “2018 Volkswagen Golf engine code DKFA” is more useful than “what does K mean on an engine.” If the marking is dirty or corroded, clean it gently and photograph it under angled light before deciding whether a character is a letter or a number.

Related: how to decode a Volkswagen engine number.

Official sources

• NHTSA: VIN decoder guidance
• NHTSA vPIC: decoded vehicle and engine fields
• Ford owner information: VIN field overview
• Perkins: manufacturer-specific engine nomenclature example