Are you wasting money on premium fuel if your car doesn't need it? | Fuel Tips

Staff
By Staff Writer
Feb 21, 2022 | Sunoco, Fuel Tips, gasoline, Premium Fuel | Posted in Features | From the Dec. 2021 issue | Never miss an article

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If the owner’s manual calls for 87- or 89-octane gasoline, are you wasting your money by filling up the tank with 93? As with most things in life, it depends. 

What Is Octane?

Search for the term “high octane” and you’ll find all kinds of results: high-octane workouts, high-octane coffee, and even high-octane fishing charters. 

“The word octane is sold as power,” notes Zachary Santner, technical specialist with Sunoco, “which is ironic because the word octane has nothing to do with that.”

Octane does not measure energy content, he continues. Octane is a measurement of resistance to autoignition–also known as pre-ignition, pinging and knock. 

The take-home message here: If an engine isn’t knocking with a lower-grade fuel, a higher-octane fuel isn’t going to provide any performance advantage. (Modern engines can automatically retune themselves when encountering pre-ignition, meaning you likely won’t hear it, so Santner recommends simply consulting the owner’s manual regarding a car’s octane requirements–assuming, of course, that things under the hood are still stock.)

What Makes Fuel Premium?

Premium fuel isn’t just defined by increased octane. It is, in simple terms, a more refined product, meaning extra steps are taken to remove impurities.

Those impurities include substances like gum and varnish that, over time, can build up inside injectors and combustion chambers. That black stuff that sometimes collects inside fuel injectors or on the backside of the intake valves? Blame gum and varnish for some of that.

Premium fuel is also more stable, so it has a longer shelf life. “The refining process to create higher-octane fuels also helps to reduce unstable hydrocarbons,” Santner explains. Those unstable hydrocarbons can be heavier and less likely to evaporate, leaving behind those gums and varnishes that can cause engine issues.

So, why don’t most people run into problems using lower-grade fuel, assuming that it’s okay for their engine? Because they’re burning it up soon after purchasing it. “Regular grade gas is designed to be consumed quickly as an economy fuel,” Santner notes.

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Comments
jerel77494
jerel77494 New Reader
11/23/21 8:39 a.m.

I had a Nissan Maxima, the last of the front engine-rear drive models, and it always ran stronger on premium.  It didn't knock on regular either.

Carman944
Carman944 New Reader
11/23/21 12:28 p.m.

I owned an auto repair shop in NW Indiana from 1981 thru 2006.  Looking back it was the worst time to start an automotive repair business with ALL the changes going on with cars at the time. 

Complex emission control systems, Computers, ABS brakes, Digital dashes, RWD  to FWD, distributors losing out to coil packs, several carburetor modifications then fuel injection in several different forms, the list goes on. More changes in the decade of the 80's than the prior 50 years!

We "fixed" quite a lot of drivability problems just by having our customer "switch" to Premium Grade Fuel (mostly Amoco back then).  Most problems we saw were carbon buildup over time affecting fuel injectors & some valve sealing issues.  Usually around 60-80,000 miles. Like smoking cigarettes, you don't get lung problems until a later on. The Premium Grade fuels, like the article states, are a "better" grade (NOT just higher Octane) with a  better detergent package and being more stable.

We were able to track this very accurately over time as our customer base was very solid with some being 2 or 3 generations of drivers.  We could have easily made more money doing repairs but if the "switch" solved the problem (hard starting, rough idle, hesitation, etc) The customer was happy & told their friends about us which made us both happy in the long run...

MrFancypants
MrFancypants Reader
11/23/21 1:23 p.m.

In reply to Carman944 :

Is it still true today that higher octane fuels get better detergents? Have you noticed a difference over say... the last 20 years compared to the previous 20?

Toyman01 + Sized and
Toyman01 + Sized and GRM+ Memberand MegaDork
11/23/21 1:32 p.m.

Honda recommends premium for the G1 Ridgeline when towing over 3500 pounds. 

A post on the Ridgeline forums by Gary Flint, an engineer on the Ridgeline, states that peak HP goes from 247 to 258 when switching from regular to premium. Peak torque goes from 32.4 kg-m to 34 kg-m with the same switch. He also states that an increase in fuel economy is often but not always noticed due to how the transmission responded to the extra torque. The fuel economy is more noticeable in high-load situations, lower temps, and climbing grades. 

I run regular 99% of the time with the occasional tank of premium. 

alfadriver
alfadriver MegaDork
11/23/21 1:40 p.m.
MrFancypants said:

In reply to Carman944 :

Is it still true today that higher octane fuels get better detergents? Have you noticed a difference over say... the last 20 years compared to the previous 20?

It's not what it used to be- as fuel now has to have specific detergent packages in them for all fuels.  Part of having SULEV30 cars last for 150k miles.  If companies have higher in premium, it's a lot less of a difference compared when I was interning with Chevron back in '89.

z31maniac
z31maniac MegaDork
11/23/21 1:49 p.m.
jerel77494 said:

I had a Nissan Maxima, the last of the front engine-rear drive models, and it always ran stronger on premium.  It didn't knock on regular either.

Am I missing something?

When did Maxima's become rear drive?

Marjorie Suddard
Marjorie Suddard General Manager
11/23/21 1:54 p.m.
z31maniac said:
jerel77494 said:

I had a Nissan Maxima, the last of the front engine-rear drive models, and it always ran stronger on premium.  It didn't knock on regular either.

Am I missing something?

When did Maximas STOP BEING rear drive?

Fixed that for you. (And pretty sure the answer is 1985, the year after we started the magazine.)

Margie

Ranger50
Ranger50 MegaDork
11/23/21 2:01 p.m.

I can say even at 18mpg and a tune, 91-93 premium I feel has made my Avalanche less failure prone. Knock on wood, troublefree for the 170k miles I've used premium...

ShawnG
ShawnG UltimaDork
11/23/21 2:57 p.m.

In Canada, most of the stuff that isn't premium has 10% ethanol in it and we've found that the fuel goes stale much faster with ethanol.

bobzilla
bobzilla MegaDork
11/23/21 3:03 p.m.

In reply to ShawnG :

Even the premium down here has 5-10% E. Hate it. The Rio is the first car I've had that under the right conditions Premium fuel helps. I'll run about every 3rd tank of premium. Holds 10 gal, usually fill with about 6-ish so it's probabl closer to 89 octane average than 87.

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