Better MPG with premium spark plugs?

I have an '87 CRX Si that runs great and gets the expected mpg. Will I
get better gas mileage with premium spark plugs and wires?


Thanks,

Greg

 

I would say that decent plugs might do a little....probably better
gettin new plugs/wires/rotor etc....BUT DONT spend your money on "split
fire" type they are a scam and very expensive.

 

My '87 Integra ran best (typical commuter driving, not racing) with the
standard NGKs. I tried Bosch Platinums and they performed worse. Never
tried premium wires, replaced OEM with OEM. Routinely replaced
cap/rotor every 30K, air filters at 20K. I used moderately sporty tires
inflated to about 35 psi. My Integra delivered improved mpg with
synthetic oil. I could get 36-38 mpg out of it on the highway moving
right along with traffic (70+ mph) vs the EPA rating of 30 mpg.
Overall, I got about 32 mpg. Probably the best compromise between
utility/economy/fun-to-drive I've ever owned. [Crushed like a tin can
when a Tarus wagon plowed into it's rear end so I'd have to say safety
was also compromised.]

YMMV.

 

wrote in

Unless your current setup is worn or defective and
produces a poor spark, no.

 

it depends on what you mean by "premium". if it's something like ngk
iridiums, and the rest of your ignition system is perfect and new, you
can get maybe 1-2%. it's probably more important to ensure your
distributor cap and leads are in good condition.

 

From NGK Spark Plugs web site:

Frequently Asked Questions

Q: How much of a performance improvement can I expect from changing
plugs?

A: A common misconception is that changing spark plugs will result in a
large power increase. In most cases, removing even seriously worn out
spark plugs will only result in very modest power gains, typically
about 1-2% of total engine output. This could be even less for
computer-controlled vehicles, primarily because most newer vehicles
have more powerful ignition systems and the vehicle's computer can make
adjustments so that vehicle operation seems smoother and more seamless.

Many people think that simply supplying more spark to the firing tip
can and will combust more fuel. What they don't understand is that most
newer cars' engines are so efficient that they are already burning all
of the available fuel. Simply adding more spark voltage can't burn more
fuel because there is no more fuel to burn.

When a stock or near-stock engine is given a fresh set of spark plugs,
peak efficiency is restored. The power gains that come from this
restored state of tune are usually minimal. Any company that tells you
that their spark plug will provide significant gains in power in a
stock or near-stock engine is making blanket statements that may not be
supportable.

 

eh? you're very confused. mixture ratios vary, and spark energy
requirements for complete combustion vary too, by over ten-fold. part
of the ability of the plug to deliver those energy requirements are
determined by things like electrode conductivity and morphology, i.e.
design. hence, different plugs /can/ affect power output. sheesh, go
to a library rather than regurgitate garbage off the net will you?

 

not enough to make up the difference in price. the only "premium" wires
are OEM, and plugs are whatever ND or NGK the sticker under the hood
calls for.

youll be better off making sure it stays in proper tune, change the oil
every 5k, keep the tires inflated and the air filter clean.

 

i definitely noticed a difference in the girlfriends RAV4 once it hit
60k by replacing the OEM platinum plugs with new ones. the idle smoothed
out noticeably.

 

Maybe you should check the total resistance of a modern ignition system.
Between the coil, distributor resistor, resistor wires, and plug
resistor you can easily end up with over 50000 Ohms. How does a 0.001
Ohm difference in the plug tip matter?

It is true that the voltage needs vary vastly with compression and the
electrode shape. I am unaware of any modern car that needs a pointed
electrode to achieve a proper spark. They all have enough spare voltage
and dv/dt to work with a plug that has been mildly worn to a dome.

Also, modern low emission engines maintain the proper air/fuel ratio
underneath the spark plug even when the rest of the chamber is lean.
It's a valve and injector timing trick.

 

My .02 is that it's WAY more important to gap the OEM replacement plugs
to the correct gap than it is to buy some trendy exotic split-fingered
ones.

 

Yes, I've noticed the same thing with older plugs. When a difference
like that is noticed, you know the factory specified interval has been
stretched too long. I personally change plugs 30K miles.

But replacing an old but properly working plug at the end of its
service life may not give you more than 1-2% improvement with modern
ignition system. Of course, how NGK arrivies at 1-2% is a different
story.

 

I agree with Kevin that a properly working iginition system is well
capable of handling the voltage variations needed to spark the gap
within the specified service interval of the plug. So changing out a
good old plug at the end of its service life with a good new plug won't
give you that much, as NGK stated, 1-2%.

 

This is a very good point, however...

Maybe I'm just being silly, but it seems to me that more voltage is
simply better (within reason - if it's enough to breach the ceramic,
that's a problem, but assuming that's not gonna happen...)

You have two electrodes and an air gap. You need to generate enough
voltage to cause a spark to jump that gap. The stronger the spark, the
less likely it is that you'll get a misfire. The actual resistance may
vary depending on the air/fuel mix floating through the gap at any given
time, but in any event, you want a nice hot spark to ignite it: if the
mix provides a higher resistance, you need more voltage to create the
arc; if the resistance is lower, the arc may occur at a lower voltage
and not be hot enough to ignite the mixture - either way, more voltage
is better. I can't imagine any instance you'd actually want LESS
voltage across the gap.

True - the shape of the electrodes isn't as much a problem as having the
electrode(s) wear down, thus increasing the gap excessively, or having
deposits build up on them, thus decreasing the gap significantly, or
adding "insulation" to them, thus reducing the spark efficiency.

The spark plug is a pretty simple device, after all... its operation and
design really hasn't changed that much in the last, oh, hundred years or
so...

 

ok, make that "thermal conductivity".

it doesn't much when the plugs are new because the electrodes are nice &
square, and those sharp angles have higher emissivity. but those sharp
edges quickly erode, so skinny electrodes that can take the
thermal/chemical environment make for better spark quality over time.
add to that the fact that skinny electrodes have higher emissivity than
fat ones day one, and retain it over time, and you /do/ have a better plug.

red herring.

 

| > >>From NGK Spark Plugs web site:
I avoid NGK ; wears fstr than NipponDenso / Champion.

| > > misconception is that changing spark plugs will result in a
| > > large power increase.
Bullshit ; changing from plugs with ( 4k ohm ) resistors to plugs w-o will
get more amperes i.e. broader sparks, fstr burn, 5% more torque, 2% less
noise, enable slower idling & a bigger gap for longer & even broader
sparks ( another 1% more torque ).
If replaced by plugs with electric wind design, then even fstr burn & more
torque.

 

What plugs & wires do you recommend?