the difference between fuels at the gas pump


difference between fuel at the gas pump

Difference between Regular and Premium Fuel

With gas prices remaining well under what they were in 2012 and 2013 people are not nearly as worried about the prices of octane and what corners they can cut to reduce the expense at the pump.

On the otherhand it’s not like we are paying a nickel for a gallon of gas, and nobody really wants to pay for premium gas. Is premium gas really worth the extra money or is the “higher octane fuel” just a bunch of bologna? In this article I’ll discuss the differences between the options you have at the gas station and whether you should adhere to purchasing a certain octane fuel.

So What’s the Real Difference?

Well there is the obvious one, premium gas depending on the area you live in will run up to a dollar more than 87. So what do the numbers refer to? They refer to the octane rating which measures the different volatility levels of the gasoline. A 93 Octane level gas is less volatile than an 89 and an 89 is less volatile than 87. Volatility in a nutshell refers to how quickly the gas will combust/explode. You might expect that higher level octane fuel is more volatile but the opposite is true.

Myths About Premium Fuel

Doesn’t premium gas have additional additives and detergents? I’ve noticed that many people believe that premium fuel has additives in it that help extend the longevity of the engine. Unfortunately, this simply is not true. Gas companies in the U.S have to meet a strict quality standard, so all fuels besides octane level are created equal.

So Why Do High Performance Engines Require 93?

If you’ve owned different types of vehicles over the years you probably have noticed that they require different octane level fuels. BMWs, Mercedes, Lexus’s and other higher performance engines usually require 93. These vehicles require higher octane fuel because in a high performance engine the piston compression is higher and the engine does not need higher volatility gasoline found in 87.

Other cars such as most Hondas, Toyotas, Fords, Chevrolets, etc typically only require 87. This is a significant difference, adding up to hundreds of dollars over a year of driving a vehicle. The engines in most of these vehicles have lower compression ratios which require higher volatility for the vehicle to perform correctly.

So Can You Put 87 in a “93 Only” Car?

Short answer is yes, but you shouldn’t and there will be a noticeable downgrade in performance. Putting lower grade fuel in a vehicle that calls for 93 can cause pre-ignition. The engines pistons may not fully compress and this can result in engine damage from “knocking”. Don’t get me wrong I have seen plenty of people put cheaper fuel in high performance cars because they believed that the higher octane was a load of crap. Unfortunately for them their engine likely did not last as long as it should have and the cars ran like garbage. It sucks to have to put the expensive fuel in performance vehicles but it’s well worth the added cost.

On the Otherhand…

On the otherhand modern day cars have knock sensors that help with mitigating the potential damage that putting lower octane gasoline in could cause. Knock sensors can help correct the problem by retarding the spark timing in the engine. However, even with modern day engines you are still exposing your car to the possibility of engine knock from lower octane fuel.

A Little Story

I once drove out to buy an old, high mileage 1998 BMW E36. The car looked gorgeous and I was stunned to see that the seller was only selling it for $3000. I did a test drive and I noticed that the engine was running rough. So I popped the hood and looked around and asked the guy a few questions. On a whim, I asked him what fuel he put in the car and he said he had always put 87 in. I then told the guy to have a nice day, and thought “if this guy is stupid enough to put cheap fuel in a BMW for years I wander what else he’s done?”.

What About 91 in 87?

I used to swear that putting 91 in my old beat up truck made it drive better. One day I finally did some research and discovered that I was just pissing away cash. If the engine calls for 87 octane gas than the timing is set for 87 octane. Nothing different happens, except your wallet is a little lighter.

Are You Unsure What Gas Your Vehicle Should Take?

Although this might seem obvious I have had too many incidents of people putting in the wrong type of gas simply because they did not know what the engine called for. If your unsure, check the gas cap. Many cars that require higher octane fuel will state “premium only” either on the gas cap or somewhere around the gas cap. If the vehicle does not, the information will certainly be in the owner’s manual.

What About “Flex Fuel”?

difference between gas at the fuel pump flex fuel

In recent years auto manufacturers have come up with an even cheaper alternative gasoline than 87, which is called Flex Fuel. Flex Fuel or E85 is a blend of 85% ethanol and 15% gasoline that can only be used in cars that are specially designed for it. GM has a lot of newer vehicles that can take “flex fuel”. Please do not put flex fuel in a vehicle that does not state “flex fuel” somewhere on it or in the owner’s manual. Flex fuel has some benefits because it is significantly cheaper at the pump than 87, but it also has lower fuel mileage than normal gasoline. The other problem with flex fuel is that most gas stations still don’t carry it, so it may not even be a consideration if your in an area that is flex fuel dry.

If your car does have the flex fuel option you can put either 87 or flex fuel in. Putting flex fuel in vehicles that are not designed for it can cause engine damage and poor performance so do not put flex fuel in a car that takes standard gasoline.

Conclusion

I understand that it’s tempting to put lower grade gasoline in your vehicle, and the temptation gets stronger when gas prices jolt up. However, the safest option for your engine and for your wallet is to stick to the fuel that the engine was designed to accept. Hope this article helped with understanding the differences in gas types!

Stephen Metellus

I am a BMW enthusiast and owner of abetterbmw.com! I have been repairing, flipping, and parting out BMWs for nearly ten years. I love these vehicles and I hope you will find my articles and YouTube channel helpful for whatever BMW project you have in store!

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