Modern Rodding STARTING OVER
A headshot picture of Brian Brennan grinning
By Brian Brennan
Gasoline … Fact vs. Fiction

hose of us who call ourselves hot rodders are the de facto “fountain of automotive knowledge” in each of our neighborhoods. I live in a “very nice” neighborhood. My definition of a very nice neighborhood is one where the cars in one’s driveway have four wheels and tires (with air). And, when there is an oil change, the discarded oil is taken to a recycle center rather then used to kill weeds along the fence line. (I know these things because I once lived there.)

There are any number of topics my neighbors continually seek me for advice. For instance: “What type of tires should I use?” “How often should I change my oil, and what oil should I use?” But the one that creates the greatest amount of conversation: “What brand and octane of gasoline should I use?” This topic has the least amount of clarity, has an immediate impact on one’s wallet, and is the current topic of conversation at every doughnut run, backyard barbecue, and weekday lunch gathering in the country. (Remember, I live in California, the land of exceptionally high gas taxes and the highest cost of a gallon of gasoline. It’s all any of us talk about.)

As to the brand of gasoline, that’s pretty much one of personal choice. There are some aspects that do make a difference. The biggest is purchasing a gasoline that is rated “Top Tier.” If you want a gasoline that is proven to work best with fuel-injected engines, then Top Tier is your choice. Many of today’s automotive manufacturers—such as General Motors, Ford, and Stellantis—recommend a Top Tier fuel. More and more discount gas stations are carrying Top Tier products. Oftentimes these stations receive some of their monthly shipments from Top Tier suppliers anyway.

Is Top Tier gasoline worth it? An independent study by the not-for profit American Automobile Association (AAA) has found that while Top Tier gas is more expensive it can, on average, help you to obtain 5 percent better fuel economy. In the long haul you are saving money and your car’s engine will run better.

Now what about the “grade” of gasoline you use? The octane rating can vary from one state to another. For instance, California typically rates its gasolines at 87, 89, and 91 octanes. Yet other states may have 87, 89, and 93. And some states have 85, 88, and 91. Some of the very large box stores offer two octane ratings of 87 and 91, and that’s where the fun begins.

In this time of literally skyrocketing fuel costs, the basic question is, “What octane should I run in my car?” While this fundamental question and answer applies to your handful of family cars it also applies to your hot rod. I have seen time and time again where rodders use a higher-rated octane gas in their hot rod and this can be a waste of money. Unless you understand the benefits of higher octane and storage.

Here’s the crux of the question: “Does high-octane fuel last longer in storage?”

Fundamentally, the answer to that question is, “Yes.”

If your hot rod (or any car) can function on regular octane fuels, such as 85 or 88, then that’s what you should be using. Keep this in mind as it is crucial; hot rods throughout the country are liable to storage anywhere from one to six months, sometimes even longer. Only if your factory manual (on your family car) or the tech sheet you received with your crate engine or the builder of your engine specifies that you “must run” the 91- or 93-octane gasoline should you use the higher priced gas. This is an important decision since the premium octane (91 or 93) can be anywhere from 15 to 50 cents more per gallon, making a great impact on your fuel costs. This is particularly true for those powerplants that run on a computer and can sense the octane rating and will adjust engine timing.

We do know that 93-octane fuels are more refined than their lesser octane family of fuels. These higher-octane fuels contain more refined and stable hydrocarbons. Research tells us that these stable hydrocarbons can last two to three times longer than 87-octane gas. The 87-octane gasolines can begin to degrade within three months whereas 93-octane often will last closer to nine months before degradation takes place.

Keep this in mind, Top Tier gasoline and octane ratings have nothing to do with each other. Top Tier standards means the gasoline has a higher level of engine-cleaning additives than non–Top Tier gasoline. Octane rating effectively means a gasoline’s ability to resist engine knocking during the combustion cycle (premature detonation). A premium fuel (91- or 93-octane) is intended for performance engines (regardless of the number of cylinders) that typically has a higher compression ratio.

It should also be noted that mid-grade (octane) rated fuels are from a bygone era and pretty much aren’t required today. According to the U.S. Energy Information Administration, about 88 percent of gasoline sold is regular (85 or 87), 11 percent is premium (91 or 93), leaving just 1 percent to midgrade.

So, for those who want to be conscious of the money you spend, and right now and for the foreseeable future this is critical, on gasoline make sure to select the proper brand of fuel and the octane rating. Keep in mind driving performance and storage as these two criteria will have an impact on which brand and octane you select.

Modern Rodding
VOLUME 3 • ISSUE 23 • 2022