I live in Texas and drive a Honda Accord, and I've heard that using 87 regular fuel is fine.

However, seeing a friend who insists that using 89 is better makes me think, "Wouldn't it be better for the car to spend a little more and use 89?"

One friend drives a 20-year-old Mercedes that is supposed to use 91 premium fuel. But he has been using regular 87 for a long time without any issues.

On the other hand, another friend insists on using only 91 in his newly purchased Volkswagen Passat, saying, "German cars need premium fuel."

With such extreme opinions, it can be confusing to know what is right.

In reality, the answer is all in the manual. Most Japanese cars like the Honda Accord are designed for 87 regular fuel, so using 89 or 91 doesn't significantly change performance.

However, during long high-speed drives or in hot summer conditions when the engine is under load, it may feel a bit smoother with higher octane fuel. That's why 89 exists as a middle option.

Conversely, European cars like Mercedes, BMW, Audi, and Volkswagen often have high-compression turbo engines, so they usually recommend 91 or higher.

This is to prevent knocking. However, it's often "recommended" rather than "required," so using 87 won't immediately cause a breakdown; it may just result in slightly lower power or fuel efficiency.

So, for my friend with the old Mercedes, using 87 might not be a big issue, while my friend with the new car is just being cautious by sticking to 91.

Ultimately, it seems to come down to personal preference. To keep a car for a long time, following the manufacturer's recommendations is the best approach, and it's also the most economical.

Using 91 in a car designed for 87 won't double the engine's lifespan.

But when filling up, pressing the 89 or 91 button does give a feeling of taking better care of the car.

In summary, Japanese cars generally do fine with 87, while European cars are safer with 91 or higher.

However, using 87 won't immediately damage the car.

The important thing is what my car manual says and what maintenance costs I can afford.

So today, I will just put the cheapest 87 in my Accord.