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I have been thinking about taking my car (an AWD Ford Escape 2014) for a road trip to Mexico or maybe as long further south as I can find paved roads.

Is there a risk that the regular unleaded gasoline in Mexico or the central american countries messes up the car?

(Here I am referring to damage to the engine or parts of the fuel supply.)

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    @pnuts I'm with you on the ethanol, but octane is not a measure of quality or purity— it's certainly possible in the U.S. for "premium" gas to be worse than "regular" as less of it is consumed, meaning it has more time to oxidize and to absorb contaminants. It's water and rust and other sediment that will do in an engine, and I do not expect tank inspections in Latin America to be as robust as they are in the U.S.
    – choster
    Commented Jan 28, 2015 at 18:28

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It very much depends on what you mean by mess up. For the purpose of this answer I will assume you meant engine damage linked to combustible type, rather than other possibly infrastructure-related issues.

This guy seems to have driven quite a few kilometres in South America, and can thus provide some useful hands-on experience. Probably worth a reading.

Understanding Octane Ratings

Fuel octane ratings indicate the likelihood of the fuel detonating when subject to compression. A higher-octane fuel is therefore capable of withstanding higher compressions than a lower-octane. Compression is an intrinsic phase of the correct operation of an internal combustion engine. Compression results in an increase of temperature, and can therefore cause low-octane fuel to ignite. However fuel ignition is a precisely-timed operation, in that the ignition should be commanded by the spark plug only, when the piston reaches a precise point in its stroke. Pre-ignition caused by spontaneous detonation can be harmful to the engine.

Mexico and USA Use Comparable Octane Ratings

Both the USA and Mexico display octane rating in Anti-Knock Index (AKI), which means that the octane values you read on Mexican filling stations will be comparable to those back home. Mexican unleaded petrol comes in two octane ratings: 87AKI and 92AKI. Hence pick the rating that most closely resembles the one you normally use in the US and you should be safe.

Comparing Octane Ratings

In case you were to drive in countries that use an octane rating different than AKI (usually this would be Research Octane Number RON), you could use this very heplful conversion table from wikipedia, which states that:

  • 87 AKI is ≃ 90/91/92 RON
  • 92 AKI is ≃ 95/96/97/98 RON

Guatemala and Costa Rica, for example, seem indeed to use RON ratings.

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  • Thank you for your answer, JoErNanO. I have updated my question because I was indeed referring specifically to the type of damage you are discussing. Would you know what the situation is with the gasoline in the Central American countries?
    – user24294
    Commented Jan 28, 2015 at 18:59
  • @codeworks I added a bit of information. Off the top of my head I don't know about every country in Central America. Usually when I drive there I rent a car, so I assume the engine can take the local petrol. Also note that the issues choster mentions here might not be related to fuel octane rating, but can still cause damage to the engine.
    – JoErNanO ♦
    Commented Jan 28, 2015 at 19:20
  • another important information is Ethanol concentration, because some countries use high Ethanol gas, for example AFAIK Brazil uses E85 which may be incompatible with low Ethanol vehicles
    – phuclv
    Commented Apr 28, 2016 at 9:13

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