Short answer. It depends on what was said. Under Article 1546, a statement of fact that naturally induces the purchase and is relied on becomes an express warranty. A pure opinion about quality — unless the seller spoke as an expert and the buyer relied on it — is not a warranty. Sales talk is not automatically binding.
What the law says
Any affirmation of fact or any promise by the seller relating to the thing is an express warranty if the natural tendency of such affirmation or promise is to induce the buyer to purchase the same, and if the buyer purchases the thing relying thereon.
Civil Code, Article 1546 — Express Warranty Versus Dealer's Talk. Read the full provision →
When a sales statement becomes an express warranty
Article 1546 of the Civil Code draws the line between an express warranty and mere dealer's talk. An affirmation of fact or a promise by the seller about the thing is an express warranty when two conditions are met: the natural tendency of the statement is to induce the buyer to purchase, and the buyer actually purchases relying on it. So "this engine has never been in an accident" is a factual claim — if it induces the sale and the buyer relies on it, it is a warranty. If the engine was, in fact, in an accident, the seller is in breach.
What is not a warranty: opinion and value statements
Not every enthusiastic claim by a seller becomes enforceable. Article 1546 specifically excludes from warranty protection any affirmation of the value of the thing and any statement that is merely the seller's opinion. "This is the best car I've ever sold" or "the price is very fair for what you get" are the kind of statements the law treats as sales talk — puffing that a reasonable buyer should not take as a binding representation of fact. The law places the risk of such statements on the buyer, who is expected to verify quality independently.
The expert exception for opinion statements
Article 1546 contains one significant exception to the rule that opinions are not warranties. If the seller presented the opinion as an expert and the buyer relied on it, the opinion can be treated as a warranty. A mechanic who sells a car and opines on its mechanical soundness in a professional capacity is in a different position from a private individual with no technical background. The buyer's reliance on expert opinion is objectively reasonable in a way that reliance on lay puffery is not.
Practical test: fact or opinion?
In a dispute, the central question is whether the seller's statement was an affirmation of fact or merely an expression of opinion. Concrete, verifiable claims — mileage, age of a component, presence or absence of defects, specific performance specifications — tend to be factual. Vague assessments of quality, value comparisons, and expressions of the seller's subjective view tend to be opinion. The line is not always obvious, and the context of how a statement was made — written guarantees, oral representations before signing, specific technical claims versus general enthusiasm — shapes how a court would classify it.