Why VINlist would rather leave a gap than guess
Check a used car's VIN on VINlist and some fields may come back empty: the engine, the power, the gearbox. That's on purpose. A decoder that fills every field looks more helpful, but where it doesn't know, it's guessing, and a confident wrong answer about a car You're about to buy is worse than an honest blank.
A V6 that became a four-cylinder
VINlist's decoder starts with what the VIN itself says, then fills in the rest, like power, fuel, gearbox and dimensions, from our catalog of models and their versions. The old decoder did that whenever the model matched. One of the VINs it decoded belonged to a Honda Accord with a V6. Our catalog had only the four-cylinder versions of that Accord, so the decoder took the power, fuel and gearbox from a four-cylinder. The page described a car that doesn't exist: a V6 by its VIN, a four-cylinder by everything else.
Why it matters when You're buying
The engine decides more than performance. It decides the price, the fuel bill, insurance and tax, which parts fit and what tends to go wrong. A wrong engine on a decoder page can do damage both ways. It can make an honest seller look like a liar, because his ad says V6 and the decoder says otherwise. Or it can make a dishonest ad look confirmed. Either way You'd be deciding on something false.
The rule now
When I rebuilt the server in September, the new decoder got one rule: it fills engine details from the catalog only when the engine the VIN states matches one of the catalog's engines, within 5% on engine size or 10% on power. If nothing matches, it keeps what the VIN said and leaves the rest empty.
I checked the new decoder against the old one on 130 real VINs that visitors had looked up. 105 came out the same. The other 25 changed, and every one of them was this rule: where the old decoder guessed, the new one leaves a gap. The technical side is in the article about the rewrite.
The other kind of gap
Many European VINs don't record the engine at all. Volkswagen, Ford and Fiat, among others, use the same VIN characters for every engine of a model, so the VIN alone can't tell a 1.0 from a 2.0. For those cars VINlist lists the versions the manufacturer offered for that model and year, and leaves the engine empty until that exact car is confirmed.
What to do with an empty field
- Ask the seller for a photo of the registration certificate. In the EU it uses the same codes everywhere: P.1 is the engine size, P.2 the power in kilowatts, P.3 the fuel.
- Compare them with the ad, and with the versions VINlist lists for that model and year.
- At the viewing, look at the car itself. The engine code is on the engine, and the service history usually names it too.
Gaps get filled
Every VIN someone checks teaches the decoder something: patterns it didn't know are researched and saved, and versions missing from the catalog get added. A gap today is often a full answer next week. What won't change is the order: a fact, or nothing. A blank says "we don't know yet". A guess says something false with a straight face.
