How to Find Engine Type by VIN (and Catch an Engine Swap)

To find the engine type from a VIN, run the full 17 characters through NHTSA's free vPIC decoder and read the engine fields: displacement, cylinders, fuel type, and sometimes an engine model name. On many US-market cars and trucks the engine is encoded in one of characters 4 through 8, very often the 8th, but the maker decides which spot, so don't guess from a chart. Then check the car itself, because a VIN only tells you what engine left the factory. If the label under the hood says something else, you may be looking at a swap.

What the VIN is required to say about the engine

Federal rules make the engine part of the VIN, but they let each automaker choose how to write it. Under 49 CFR 565.15, characters 4 through 8 (the vehicle descriptor section) must let you decipher engine type for passenger cars, trucks, multipurpose vehicles, buses, and motorcycles. The same rule says the characters used and their placement within that section are up to the manufacturer, as long as the maker supplies the decoding information. That one sentence is why "the 8th digit is always the engine" falls apart: plenty of makers use it, and some put the engine code elsewhere.

If you want the bigger picture of those five characters, our guide to VIN digits 4 through 8 covers them, and the first three are explained in what the WMI means. Character 10 gives the model year, which matters here because engine codes get reused across years; see the 10th digit and model year.

How to decode it with vPIC, with a real example

Go to the NHTSA vPIC decoder, paste the full VIN, and look for the engine section in the results. NHTSA notes that the decoder data is reported by the manufacturer, so a blank field usually means the maker never supplied that detail. Partial VINs work too, which makes it easy to see how one character changes the result.

I ran three partial VINs through the vPIC API on Sunday, November 8, 2026, all starting 1FTFW1E for a 2022 Ford F-150 and differing only in the 8th character:

• 8th character 5: 5.0 liter, 8 cylinders, V-shaped, gasoline.
• 8th character 8: 3.5 liter, 6 cylinders, listed as GTDI, gasoline.
• 8th character P: 2.7 liter, 6 cylinders, gasoline.

So on that truck the 8th position really is the engine code. On another brand, or another year, it might not be. CARFAX's VIN guide says the same thing in plainer words: characters 4 through 8 identify brand, model, body style, engine type, transmission and more. When the decoder shows the wrong trim or a vague engine, it is usually a data gap, which we dig into in why a VIN decoder shows the wrong trim.

Cross-check the VIN against the engine bay

A VIN describes the car as built. To know what is in it now, look under the hood. Federal emissions rules in 40 CFR 86.1807-01 require a permanent "Vehicle Emission Control Information" label in a readily visible spot in the engine compartment, showing engine displacement and the test group, and it must be attached so it cannot be removed without destroying it. If the VIN decodes to a 2.7 and that label says 5.0, something changed.

Next, look for numbers on the engine itself. Many engines carry a stamped or labeled engine number or partial VIN, and its location depends on the maker. We cover where to look and what a mismatch means in engine number vs VIN. A missing emissions label is not proof of a swap, since hoods and labels get replaced after accidents, but it is a reason to ask harder questions.

• Decode the VIN and write down displacement and cylinders.
• Read the emissions label under the hood and compare displacement.
• Count the cylinders or coil packs if you know how, or have the inspector do it.
• Check any stamped engine number or partial VIN against the dash VIN.
• Ask for receipts if the seller says the engine was replaced.

When a mismatch means an engine swap, and why you should care

Not every new engine is a problem. California's Bureau of Automotive Repair separates an engine replacement, meaning the same make, cylinder count, and engine family with original emission controls, or a configuration the maker offered for that year and model, from an engine change, which is anything else. BAR says every vehicle with an engine change must first pass a Smog Check at a Referee Center and carry a BAR Referee label inside the engine compartment, while straight replacements skip the Referee. It also cites state and federal anti-tampering laws against changing the certified emissions setup.

That gives a California buyer a cheap tell: a car that should have a Referee label but does not. Other states handle it differently or barely at all, so read engine swaps, titles, and emissions checks before you buy anything modified. Honestly, a clean swap with receipts and a Referee label rarely burns anyone. The deal that hurts is a truck listed at V8 money whose VIN decodes to a V6, with a seller who cannot say where the bigger engine came from.

Can a history report show the engine was replaced?

Sometimes. If the work went through a dealer or a shop that reports service records, a report may show it; a driveway swap usually leaves no trace. Our post on whether CARFAX shows engine replacement covers what to look for. Look, I'd never take a seller's PDF for this. We've seen fake report screenshots passed off as the real thing. Pull your own with the VIN off the dash. Through CarVins, which is licensed to resell CARFAX and AutoCheck but has no affiliation with CARFAX, AutoCheck, or Experian, a single report has been running roughly $4.50 to $5.50 depending on membership, a small slice of the $39.99 to $44.99 retail range; confirm at checkout.

One last habit: screenshot the vPIC result the day you look at the car. If the listing later changes its engine claim, you have the factory answer saved.

Sources

• NHTSA vPIC VIN Decoder
• eCFR: 49 CFR 565.15, VIN content requirements
• eCFR: 40 CFR 86.1807-01, vehicle emissions labeling
• California Bureau of Automotive Repair: Engine Changes
• CARFAX: VIN Lookup and decoder guide