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Is Premium Gas ok?

10K views 50 replies 27 participants last post by  mlheck 
#1 ·
So I've never used premium before, but I've read/heard that its ok to fill up the tank once every month or 2 as it "cleans" the system a bit. I've also seen/heard that it does nothing.

As a focus owner, what do you say?
 
#2 ·
I have a zetec, but I don't imagine the answer would be to different from a duratec... I say it's great, I actually observe about 4-6mpg more with 93 vs 87. I also saw a smoother idle when my plugs needed replaced...

Some argue it's just a waste of money unless you have a tune, but I have observed different...
 
#5 ·
If your putting in premium= get a tune & enjoy the power w/ it.



If your running premium fuel, Why not take advantage of the power & get a 91-93 octane tune w/ a Steeda sri? Another words= Get a tune[woot]
 
#9 ·
I'm guessing the ECU isn't aggressive enough with timing and a super sensitive knock sensor to adjust for a higher octane. I'm pretty 95% sure it's a waste of money. Some ECU's will advance the timing until the knock sensor indicates knock, and will stay right on that fine edge. I know the 2011+ Mustangs do it. I doubt the Focus Zetec/Duratec ECU is that sophisticated.
 
#11 ·
If you read the owners manual it actually says that the use of premium will make it run worse under certain conditions. Those that say they get better mpg with it are fooling themselves. High octane fuel burns SLOWER and not as easily as lower octane that is the point of it.
 
#13 ·
I ran 93 without a tune for two or three years. About a month ago I switched back to Regular 87, and I'm not noticing any difference.

I can only imagine what parts I could've bought with that money...
 
#37 ·
I can only imagine what parts I could've bought with that money...
Just doing some dirty math...

Over the span of approx. 3 years you could have saved approx. $200 by using regular fuel. Don't know how much you could buy with that. Maybe some custom floor mats and a skull shift knob? lol.
 
#18 ·
I've heard tom is better with zetecs then duratecs. I'd say go with fswerks. They might charge you to get it tuned but it's not like you would be doing it everyday and they're good quality. not saying tom isn't but sometimes you gotta pay to play.
 
#19 ·
Just to keep my hat in the pot , I know Duratec tuning as well as anyone does , with tuning from me you get a

Full custom tune

Free tune updates as you add more NA mods fs charges up to 350.00 more
Datalogging services where I take over your laptop and set up your datalog list and do the first datalog just like sitting in the car with you so you understand how to use everything , not offered through fs

If interested and have any questions please let me know
 
#21 ·
No dummy's here, We're all here to learn. BSD= Balance shaft delete. 23's/25's have a pr of balance shafts in the bottom of motor, which is driven off the crank, to smooth out the motor. The 23/25's having a longer stroke. You have a '07 zx3, so that means you have a 20 motor, so you don't have to deal w/ that, till you install a 23. It removes rotational & static weight, which makes the motor more responsive.
 
#23 ·
From wikipedia: http://en.wikipedia.org/wiki/Octane_rating

<Octane ratings are not indicators of the energy content of fuels. (See section 4 of this page and heating value). It is only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner. Where the octane number is raised by blending in ethanol, energy content per volume is reduced. >

<Many high-performance engines are designed to operate with a high maximum compression, and thus demand fuels of higher octane. A common misconception is that power output or fuel efficiency can be improved by burning fuel of higher octane than that specified by the engine manufacturer. The power output of an engine depends in part on the energy density of the fuel being burnt. Fuels of different octane ratings may have similar densities, but because switching to a higher octane fuel does not add more hydrocarbon content or oxygen, the engine cannot develop more power.>

Totally amazing about gas. Draw a 1/2 inch square and with the tip of the pencil, place 15 'dots' inside the square. One of those dots is gas. The rest (approximately) are air. That's the mixture feeding a cylinder each cycle.

Run the lower octane and trust the anti-knock sensor. Unless you are running a modified engine with high compression pistons or you have an air pump (compressor).

btw, I read that Chevron gets from 'the top' at the refinery, which is a finer and cleaner blend, with less contaminants that are found in 'the dregs' that other brands get out of the same batch.
Techron will keep the injector nozzles clean.
I have no commercial connection, just years working as a mechanic on small engines that have carburetors with main jet orifices so small that a piece of hair blocks half the fuel delivery to the cylinder.
If you can buy gas with no ethanol that would be best power and mileage.
 
#27 ·
More power with higher octane? Are we talking power like you'd see a diff in the 1/4 mile using 93 vs 87? Or is it just a tad better throttle response and smoother power delivery? MotorTrend turned a 15.8 with a SE equipped with a 5 speed and 87 octane and that's one of the quicker numbers I've seen turned with a stock MK3.
 
#33 ·
i just finished a emission analysis on an engine where i ran 87 octane all the way up to 110. tried ethanol (10% blends) and non ethanol blends. using fixed valve and spark timing. the emissions steadily increased. this was done on a low compression 305cc 14tq 1 cyl briggs and straton engine. so take the results with a grain of salt when comparing it to our motors.

i ran a electronic governor and as the octane increased it had to work harder to maintain the rpm limits i set on many pulls it exceeded the limits and took a while to bring them back down. i wasnt measuring power output but that to me means more torque. also as the octane increased the idle quality decreased.
 
#39 ·
Yup!

High Octane's purpose is to prevent pre-ignition (detonation, pinging) in high compression engines. High compression results in more efficiency/power whether it's from increased C/R (compression ratio) or from better cylinder fill (boost, flow improvements).

If the existing fuel is adequate to avoid pre-ignition, higher octane REDUCES performance for the same reason it improves it when needed - it doesn't "light off" as easily, so you don't get the well timed clean burn that is optimal for power/economy/emissions.

Best example of this I've ever seen was a motorcycle that was "de-tuned" from the factory for lower octane fuel (lower C/R), which wouldn't start when the owner of the new bike "treated" it to a tank of high octane fuel.

Like any other "performance" modification, everything has to "match" to achieve the result desired.

Cheers
 
#47 ·
0%

The fuel I'm talking about is just regular unleaded 87 with no ethanol in it at all.

Some of our stations around here keep a pump devoted to it for people who want it or need it. Lawn equipment doesn't really react well to the ethanol.
 
#48 ·
2005 Focus ST - I changed my plugs to Autolite 103 a few months back. Great increase in 1st gear torque, it really pulls much harder. I'm on my first tank of premium now - revs much faster in all gears. Both changes gave great butt-dyno feel.
 
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