Premium gas must be called premium for a reason, and therefore must be better than regular, or why else call it 'premium' right?
Premium. According to Dictionary.com, means many things!
1. A prize, bonus, or award.
2. An amount to be paid, as an insurance premium.
3. A sum above the nominal or par value of a thing
4. of exceptional quality or greater value than others of its kind; superior
and finally:
5. of higher price or cost.
Compared to premium gasoline, lower-octane fuels like 'regular' don't allow the engine to run as much ignition advance during situations calling for rapid acceleration. More ignition advance allows the engine to make more power, and accelerate more quickly. Since the engine doesn't make quite as much power with lower-octane fuels, this translates into slightly slower acceleration in cars for which premium fuel is recommended. The performance loss is a bit more noticeable in turbocharged engines. The performance loss, however, is something you will only notice if you are keeping track of your 0-60 times! This power difference is extremely low, usually in the 1% to 3% range, and will not generally be noticed. Would you notice that your 300 Horsepower car all of a sudden only had 297? No, you wouldn't.
If you had a drag car that was making 2,500 Horsepower and
you used a lower octane fuel, would you notice that it now only made 2,425 HP? Yes, then you would probably see a difference in your 1/4 mile times. You are not
driving around every day with 2,500 HP are you? If you are, let me know
and we'll go for a cruise!
There is little difference in the energy content of regular versus
premium gasoline, as they both contain about 111,400 British Thermal Units
of energy per gallon, which means that they will both burn and explode roughly the same.
Lets take a quick chemistry lesson in order to better understand our fuel.
Oil is a hydrocarbon fuel, meaning that the individual molecules contain hydrogen and carbon atoms all tied together in a chain. Gasoline is made from oil, and modern fuels are blended together in various ways with many different hydrocarbons; 200 or so. One of these is called octane, or isooctane to be precise, and it consists of 8 carbon atoms (Thus the 'oct' part), and 18 hydrogen atoms, which together make C8H18! - Wow, that was fun, wasn't it?
The reason octane is used extensively is because it has a natural tendency to resist spontaneous explosion when exposed to heat and pressure, much like what is found inside your engine! When the fuel inside your engine explodes due to heat and pressure instead of when the spark plug ignites it is commonly called 'knock' or 'Pinging'.
'Knock' is very bad, and causes harsh vibrations and a loud noise, the 'knock', which over time will seriously damage your engine. I'll go over the intricacies of the four-stroke engine in a future post.
This is why the wizards at car manufacturers came up with a 'knock' sensor many many years ago to detect the pre-ignition, or 'knock', and adjust the timing or boost accordingly to prevent damage. This was initially developed due to the huge variation found in fuels many years ago. The first incarnation of this type of detection system originated in the SAAB 'H' engine, launched in 1981 for their SAAB 900 and was called Automatic Performance Control. - and you thought all the cool stuff was just recently made!
Enough history, so lets get back to the fuel. Lets see what the numbers mean at the pump! 87 Octane, 90 Octane, even 93 Octane... that must be the best one, right? Hold on a minute! This number at the pump is not a measure of the percentage of octane actually found in your gas! Rather, it is a measure of how that gas compares with a pure mixture of octane and heptane. n-heptane (C7H16) is highly susceptible to the self ignition we spoke of earlier, and has the opposite properties to octane. At special laboratories all over the world, chemists create these 'reference fuels' and then use them in comparison with refined gasoline following the dictates of standardized measures, in order to assess the viability of gasoline blends.
"The American Society of Testing and Materials has a thick document on how you determine octane rating with this specialized one-cylinder engine," says Joseph Shepard, a mechanical engineer at the California Institute of Technology. "The higher the number the harder it is to have knock."
(www.scientificamerican.com)
The key for drivers is to know whether premium gasoline is merely recommended or if it's required by their respective manufacturers. The recommended ones are only so that the manufacturers can advertise slightly higher Horsepower numbers. The required ones were designed specifically for that fuel and are more than likely using much higher compression ratios in their engines.
Edmunds.com has compiled two lists: "premium recommended" and "premium required" for vehicles from the 2008-'13 model years (with a few 2014 model-year vehicles). If your vehicle is on the "premium recommended" list, you're OK to try switching to regular unleaded gasoline. If, on the other hand, your car is on the "premium required" list, then you have to run premium fuel. You can confirm the information on these lists by checking your owner's manual.
Recommended: Recommended
Required: Required
Ultimately the choice is up to you which fuel you want to use in your car. Lets assume for easy math a $0.10 per liter difference between regular and premium fuel. With an average fill up being around 65 liters - ish, you would be spending an extra $6.50 / tank. Lets also say you only fill up twice a month, twelve months a year. Looks like you just spent an extra $156 on fuel. You might own your car for an average of say, 5 years? There's an extra $780 in gas!
I just checked, and it looks like for my $780, I can go to Fiji! Its warm in Fiji, and I'm not the one filling up the taxi. Vanuinui vinaka ki na siga ni kua!
Matt Bourbeau
Transportation Specialist
McFadden Honda
matt@mcfaddenhonda.ca
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