The Defensoria de los Consumidores Costa Rica (Consumer Defense Costa Rica) Facebook page is recommending buying gasoline in the morning, when temperatures are low, this makes gasoline thicker.

From Facebook

Surfing the Internet you will find tons of tips suggesting ways to get more for your money, from making your car more fuel-efficient to saving money on gasoline fill-ups.

So, is it better to buy gas in the morning or not?

The science that gasoline is denser in colder temperatures and expands in higher is true, but the idea of to buy gas in the morning than in the afternoon, to save money, is a myth.

The basic facts are correct, but the advice is not. Like all liquids, expands when heated. Gasoline does expand and contract a little depending on its temperature.

But buying gas in the morning temperatures is unlikely to provide you with any noticeable savings. Why?

In the U.S., Consumer Reports actually did a study on this and found that it takes a 15C˚ (27F˚) temperature rise in the gasoline temperature, for instance, to cause the density of gasoline to decrease by 1%, while the energy content remains the same.

In Costa Rica, few places in the country experience a 15C˚shift in temperature.

Also, gasoline stations typically store their gasoline underground, where the temperature variations during the day is much less than in the air above. The result if that the temperature of the gasoline going into your tank varies very little. If at all.

From the above, we can assume that the temperature of the gasoline in the underground tank stay at a pretty steady temperature and there is no way of knowing when the gasoline in the tank was delivered, which could further affect temperature.

Using the 1% in volume increase cited by Consumer Reports, how much money does that save you? Maybe a few colones.

So, is it better to buy gas in the morning instead of the afternoon or at any other time of the day? No, not really.

Even if you were to fill up during ‘ideal’ conditions based on temperature and gasoline tanker delivery, are the savings of a few colones worth getting up early in the morning to go fill up your tank.

When is the best time of day to fill your car with gas? When you need gas and you are near a gas station.