The Octane Myth So, you're at the gas station. 87, 89, and 93 are staring you in the face. You glance over at your Mercedes and think, "Only the best for my baby." Do you question the decision you're about to make?93 is better than 87, right? Well, not always. In layman's terms, 93 octane fuel is actually a slower burning liquid for lighting on fire inside your engine. Some people will go their whole lives not knowing the difference between the different grades. Only once I learned its true purpose did I start deriving value out of its increased price at the pump. Case Study: 2007 Toyota Camry SE V6
I experimented with 93 octane a bit shortly after taking ownership of my old '07 Camry V6, in 2011. It uses Toyota's deliciously smooth 3.5L 2GR-FE V6, which specifies a minimum octane rating of 87. That's 268 naturally-aspirated horsepower, drinking the most basic fuel available in my region of the US.
There is no doubt in my mind that this car was putting out every last one of those 268 horsepower, as it's the fastest car I've owned to date. Of course, I wondered if there was any more to be had. After giving her a fresh tank of 93, I proceeded to beat the living daylights out of this car in my quest to justify the higher price. No dice. I felt nothing. Nothing changed. The same repeatable acceleration through the gears was felt each and every time. It drove just like it did with 87 octane.
Power on a Budget
What did I learn?
This was a good indication that the engine did not experience any knocking or pinging on 87 octane whatsoever. The timing had no headroom to improve from the beginning in the stock ECU maps. If I was achieving max-output on 87, 93 wouldn't get me too much above that. Granted if this car had any tuning options available, I'm sure the timing and ignition maps could be optimized in a manner that would take advantage of all that 93 octane has to offer.
I've run into a majority of car owners that would buy high octane for this car under the assumption that it's better for the car in some way. They might think it has a higher quantity of cleaning detergents and will make their engine perform better.
I've disassembled enough engines that were owned by cheapskates to know this simply isn't the case. I've seen numerous Subarus, Toyotas, and Volvos, that had pristine looking valves and I know for a fact that they were not given the royal treatment at any point in their lives, especially not high octane fuel. Those TV commercials that show premium fuel cleaning deposits off of valves are, in my eyes, a complete crock, since standard 87 doesn't cause a tangible buildup of any kind.
(Premium fuel ≠ Top tier fuel, I'm talking strictly octane)
What does higher octane offer?
There's gotta be something good about this stuff, right? Definitely. We need it!
Here's why: High octane fuel is more resistant to pre-ignition, pinging, and knocking. This is what occurs when heat and compression in the combustion chamber ignite the air/fuel mixturebefore the spark plug fires. This is terrible for your cylinder head, pistons, and valves. Our needy imports usually have engines tuned for performance, utilizing high-compression engines or turbochargers.
Thinking about emptying my wallet at the pump
For those of us that drive the less performance-oriented models of these Euro marques, I hate to see owners waste their money on premium fuel whentheir car won't take advantage of it. Even my 99 Volvo S70 AWD doesn't require premium and it came from the factory with a turbo. Drove great, too. I fed her a steady diet of 87 octane for a year before upgrading the turbo and tuning the ECU with premium fuel in mind. Now, I wouldn't dare going back, but in stock guise it was totally safe and didn't complain once.
I always recommend to first check the owner's manual, then take a look at your driving habits based on the recommendations or requirements outlined in the manual. If it lists arequirement for91+ octane, you most likely have a high compression or high pressure turbocharged engine that is simply unsafe to run on anything less. Not only would you see less performance, but you'd risk damaging your engine with 87 or 89 octane.
If the manual only recommends premium for optimum performance, it also often states a baseline requirement for the general health of your engine - usually 87. The car's ECU will analyze knock sensor data and adjust fueling/timing appropriately based on the lower octane fuel. You lose a few horsepower, but you also gain a few bucks. For people that don't care about performance, I always tend to steer them towards the minimum octane requirement. Because let's face it - Grandma isn't going to burn a valve going 25mph to the grocery store. But, everyone's car and driving styles are different.
What's your take on the great octane debate?
About the Author: Alex Fiehl
Alexis FCP's Blog Editor and an IT technician from Endwell, NY. He has over 8 years of experience working on a wide array of import makes, but lately is partial toVolvo. For some reason he just purchased aVolkswagen, and is excited to see what breaks first.
