Today we're talking about gasoline. What's the best fuel for your car? Does higher octane mean more energy or more power? If you put premium gas to a car that requires regular gas, will it improve your engine performance or gas mileage?
Hop in and we'll get going.
In the U.S, unleaded gasoline usually comes in
three great, normally we have 87 for basic or regular, 89 for plus or mid-grade
and 93 for premium. But what is octane rating and what does it mean? Octane
rating refers to how resistant the fuel is to combustion by pressure, the
higher the octane rating the more compression the fuel can withstand before it
ignites, higher octane fuels are often required or recommended for engines that
use a higher compression ratio and or use supercharging or turbocharging to force
more air into the engine.
Increasing pressure in the cylinder allows an
engine to extract more mechanical energy from a given air fuel mixture but requires
higher octane fuel to keep the mixture from pre-detonating, octane rating does not
relate directly to the power output, it has nothing to do with the energy
contained per liter or per kilogram of fuel. Fuels with a higher octane rating
are used in higher compression engines that potentially yield higher power but
such higher power comes from higher compression of the engine not necessarily
from the gasoline. Do you know why the octane numbers of gas stations in the
U.S differ from those in Europe? Europe has 95 and 99. Does this mean that Europe
uses higher octane? No, because in the U.S gas stations use pump octane number or
P-O-N but Europe uses RON, which means Research Octane Number, it's just a
matter of definition, so the American 89 octane or mid-grade is the same as a European
95 octane and the American 93 or premium grade is the same or similar to the European
99.
In 1921 an English engineer, Harry Ricardo
discovered that the more iso-octane in the fuel, the more resistant it was to
detonation, he developed the scale to measure detonation resistance. Gasoline
made up of 100% iso-octane was given an octane rating of 100. Harry's work
ultimately led to the general use of octane ratings; there are a lot of myths
about octane so answer true or false:
The different octane levels mean different
energy content?
Different octanes burn fuel hotter or colder, or
faster or slower?
Different octanes burn fuel cleaner and more
fully?
If you answered yes to any of these myths, then
unfortunately you were wrong because 1) the different octane levels all contain
the same energy content 2) they also all burn the same temperature at the same
speed 3) a clean or complete fuel burn depends not on the octane but mainly on the
air to fuel ratio in your car's combustion chamber, so let's break it down: What
happens if your car requires high octane gas but you fill it with low octane
instead?
Nowadays, modern cars have electronic control units
‘ECU”'s that can adjust engine timing and performance to operate even with
lower octane fuel, so your car will drive but engine power and fuel economy
will still suffer. Frequent use of fuel with octane lower than what your car
needs can lead to poor engine performance and eventually damage both the engine
and the emission control system. Here's why: in general, using lower octane gas
and high octane gas car means that under high pressure, gasoline will ignite
spontaneously and earlier than it should and what is called detonation that is thermal
shock will occur, this is a spontaneous uncontrolled ignition of fuel in the
engine. Detonation leads to a sharp rise in temperature and even to a possible explosion.
Will your engine survive the detonation and how do you know if or when it's happening?
Simple: you hear a knock sound from the
engine when a detonation occurs, this knock is created by pressure waves that
occur during the rapid combustion of the mixture and get reflected from the
walls of the cylinder and piston, this reduces the engine power and accelerates
the wear inside, so if detonation waves occur, the engine can be damaged or
destroyed, that's how gasoline with a lower octane rating can damage the engine
pistons if you regularly use it in a car that requires high octane. What about
the opposite scenario? Let's say your car maker requires regular unleaded gas
but you upgrade with mid-grade or premium, will this affect fuel economy or
engine performance? It depends on your driving conditions, for example: in most
cars higher octane fuel can improve performance and gas mileage and it can also
reduce carbon dioxide CO2 emissions during severe duty operate, like if you're
towing a trailer or carrying a heavy load especially in hot weather but under
normal driving conditions, you'll probably get little to no benefit in fuel
economy or engine performance. In that scenario you have to ask yourself, why
pay more for premium gas? So, is there a difference between what your car maker
requires versus what they recommend? Yes there is a difference, in general if
your vehicle requires mid-grade or premium fuel then higher octane fuel is worth
the extra cost, if your owner's manual says your car doesn't require premium
fuel but says that your vehicle will run better on higher octane fuel, in other
words it's recommended but not required, well then it's really up to you. The
cost increase is typically higher than the fuel savings but some drivers value
lower CO2 emissions and lower petroleum usage by even a small amount and for
those drivers, this is more important to them than costs. In conclusion what
fuels should you use for your car? At
minimum, use the fuel grade required by the original car manufacturer, where
can you find that information? It's always written in your car manual, if you
lost your manual you can check either the fuel door because it's usually written
there or if it's not, there it's probably on the fuel cap or if it's not there,
check the fuel gauge on your dashboard. Here's a quick cheat sheet on how
gasoline works in your car so you get to the pump, you fuel your car the gas
goes straight to the gas tank well inside the tank is a fuel pump, it pumps the
gas into your car's fuel line, the fuel filter filters out debris in a gas, next
the fuel injector sprays gas into the piston cylinder, the gas gets processed
in the engine, typically in a four stroke cycle first, air gets sucked into the
cylinder, the air and fuel mix as the piston moves downward in the cylinder, as
the piston moves back up it compresses the air and fuel mixture then the spark
plug ignites the compressed air and fuel, this causes a combustion reaction,
the liquid gas gets converted into exhaust gas which forces the piston back
down, the exhaust valve is open the exhaust gases leave the cylinder, travel
through the exhaust pipe through the catalytic converter which reduces the
pollutants into less toxic substances like carbon dioxide, nitrogen and water and
then the gas is passed through the muffler and into the air then there's gas
additives, they can work to increase the octane rating of gas, inhibit
corrosion, lubricate and allow higher compression ratio for greater efficiency
and power. However, some additives are harmful and are regulated or banned in
some countries, oftentimes gas retailers treat the gas they buy with specific additives.
Ever hear of top tier detergent gasoline? In 2004, top-tier gasoline was
developed to go beyond the minimum standard for detergent additives to better
protect engines from carbon buildup and deposits on the intake valves, nowadays
engines have become far more precise operating under tighter tolerances and higher
compression ratios with cleaner emissions and improved fuel economy and that's
why many big automakers Audi, BMW, Fiat, Chrysler automobiles, General motors,
Honda, Mercedes-Benz, Toyota and Volkswagens support top tier gas. Top tier
fuel must maintain levels of detergent additives that result in a higher
standard of engine cleanliness and performance as compared to the EPA minimum requirement
also, it can't contain metal additives.
Let's talk about Ethanol, Ethanol is an
alternative alcohol fuel, it's made from plant materials like corn and sugar,
in fact did you know that much of the corn grown in the U.S isn't eaten, popped
or creamed? Some of it is turned into Ethanol, it's added to gasoline because
it's a cost-effective way to raise the octane rating of gas, also ethanol burns
cleanly so it's also a way to help reduce emissions, ethanol can be burned in a
gasoline engine but it's less than ideal compared to gasoline, reason is it has
less chemical energy than diesel or regular gasoline but since ethanol comes
from renewable sources, it makes a lot of sense to use as much of it as we can.
Ever see the badge for E85 and wonder what that
is?
E85 is a blend of 85% ethanol and 15% Gasoline;
it's designed for use in flex fuel vehicles which can use both gasoline and a
mixture of gasoline and Ethanol, well what happens if you actually put E85 in a
non-flex fuel vehicle? Well your car may run poorly and the check engine light
might turn up but it shouldn't cause major damage to your car, just be sure to add
regular gasoline to the tank when you can, to further dilute the ethanol while
85% Ethanol is a bit high use for normal gasoline cars. A more conservative
ratio can help stretch gasoline supplies and reduce our reliance on fossil
fuels, in fact that's why at most regular gas stations these days, you might
notice a pump with a sticker that says something like “may contain up to 10%
ethanol” or a blue pump with a blend of 25, 30 or 35 % ethanol, these fuels
work just fine in most modern cars built after 2002 and that's why we see a bit
of ethanol in virtually all gasoline nowadays. You should check your owner's
manual or speak to one of the service advisors if you’re unsure.
Finally, here are some fun facts about gasoline.
Did you know that the U.S accounts for about 44% of the world's gasoline
consumption? Which country do you think has the world's largest gas reserve? You're
probably guessing somewhere in the Middle East but believe it or not it's Venezuela,
they have 298 billion barrels, compare that to the us we have just 33 billion
and you might be surprised to hear that the U.S gets more of its oil from Canada
and Mexico than it does from the Middle East.
Thank you for reading!