Mixing gas ok ?

[WRXtreme]

It does not say "catastrophic failure not covered by warranty will
occur if <91 octane is used" Performance MAY suffer but it is not
likely the average driver will notice.
You guys are so anal. I guess you think going 1 mile past the
recommended oil change will cause harm too.

I know of 2 warranty claims that were denied because the owners used lower
octane fuels (excessive knock was recorded w/ the one on his ECU..he ran 90
octane)

 

[Bonehenge]

I know of 2 warranty claims that were denied because the owners used lower
octane fuels (excessive knock was recorded w/ the one on his ECU..he ran 90
octane)

It's funny that you bring that up.

I now of several people who had non-Subaru warranty claims denied due
to data recorded and stored in ECU modules.

One was an Audi S4, where the owner chipped it, removed the chip
before service visits, and reinstalled the chip when he wasn't
expecting to visit the dealer. The Audi dealer was able to tell him
exactly what he had done to void the warranty, including how many
times the chip had been installed, and when it had been installed.

As memory gets cheaper and cheaper, how long before the car will
record everything you've done, complete with GPS coordinates from
navigation systems or Onstar? <G>

Nowadays, a hard disk wouldn't be hard or expensive to add to the ECU,
and text data is actually quite small and easy to store. Heck, it
wouldn't be hard to keep track of your acceleration, MPG for each fuel
fill, max speeds, ABS and traction control events, etc...

Barry

 

[CompUser]

You guys are so anal. I guess you think going 1 mile past the
recommended oil change will cause harm too.

Let me guess...manual boost controller!

 

[l.lichtman]

CompUser wroteclip) ECU responds only post-knock event, so damage
could already have been done; (clip)
^^^^^^^^^^^^^
Preignition knock will damage the pistons severely if it is allowed to
persist, but it takes time. Since the ECU retards the spark
immediately on detection of the "ping," there should be no damage. In
a properly timed engine, this should happen only some combination of
heavy load, high temperature and lugging. Regardless of what the
octane rating of the fuel is, there will not be preignition if these
conditions do not exist, so the ignition does no6t retard, and engine
efficiency does not suffer.

If your driving is mostly cruising on the highway, or toodling around
town at fairly light throttle, the full octane of the fuel is not being
used and I don't see why you couldn't blend down to save money. If you
drive a lot in the mountains, pull a trailer, or like to accelerate
fast, cutting the fuel octane will hurt performance.

 

[Michael]

I was just courious. I'll stick to the 93, just gonna drive it easier to
increase my milage. I'd rather be safe then sorry. My milage is crap, but i
do drive it hard and sit in alot of stop and go traffic.

 

[CompUser]

@z14g2000cwz.googlegroups.com>,
(e-mail address removed) says...

CompUser wroteclip) ECU responds only post-knock event, so damage
could already have been done; (clip)
^^^^^^^^^^^^^
Preignition knock will damage the pistons severely if it is allowed to
persist, but it takes time.

You best hope it's detonation/knock/ping, NOT
preignition. They ain't the same animal. And,
the "time" it takes for preignition to put a hole
in your piston can be as short as single event.

Since the ECU retards the spark
immediately on detection of the "ping," there should be no damage.

It responds as "immediately" as it can, it's all
after the fact.

 

[KLS]

Well, I have a 1998 Forester that just turned 216,000 miles on the
odometer, and I am still running 87 octane, as recommended in the
manual. I guess it takes longer than that for the "notorious carbon
buildup".

I would use whatever grade is specified in the manual. Saving a few
pennies on gas at the expense of the engine is false economy.
Conversely, using a higher octane than required is throwing money away.

Totally correct, and where I live, I can't always find 91 octane, only
89 or 93, so if I have a half tank of 93 in my car (and think to
remember!) I'll top off the tank with 89 to get a blend of 91. But I
won't run my car with anything less than 91 octane for engine reasons
as well as the fact that I have noticed slightly better gas mileage
with the higher octane.

 

[Bonehenge]

@z14g2000cwz.googlegroups.com>,
(e-mail address removed) says...

You best hope it's detonation/knock/ping, NOT
preignition. They ain't the same animal. And,
the "time" it takes for preignition to put a hole
in your piston can be as short as single event.

Remember the water injectors installed as aftermarket devices on motor
homes and gasoline powered trucks back in carburetor days?

The injectors mixed a small amount of water into the fuel to prevent
preignition. It didn't take long to destroy an engine with
preignition.

Barry

 

[TG]

I have had great results with "Sea Foam" 1/3rd in the brake booster vacuum
line and 2/3rds in the gas tank. TG

 

[Mark H]

Damn, you americans get crap petrol.
Here in Aus we get 98 octane... No wonder I get better economy and
acceleration than you.
but 83 octane? Shit. You must have a lot of engines blowing themselves up
due to serious knock problems... even my Toyota would refuse to run on that.

 

[Carl 1 Lucky Texan]

I think you guys go by the 'research' method.(hydrocarbon densities or
something). We use that number averaged to a 'motor' numbe acheived by
actually using a grade in an engine in a lab and measuring the output
somehow. Our pumps even list it as RON+M/2 . A pure RON is 'theoretical'
and seems inflated. But I suspect you also get a different owner's
manual with appropriate fuel recomendations for your region.

What makes our gas 'crap' is ethanol and/or methyl tertiary butyl ether.

Carl
1 Lucky Texan

 

[Mark H]

I think you guys go by the 'research' method.(hydrocarbon densities or

something). We use that number averaged to a 'motor' numbe acheived by
actually using a grade in an engine in a lab and measuring the output
somehow. Our pumps even list it as RON+M/2 . A pure RON is 'theoretical'
and seems inflated. But I suspect you also get a different owner's
manual with appropriate fuel recomendations for your region.

What makes our gas 'crap' is ethanol and/or methyl tertiary butyl ether.

Yeah, ethanol got the big FO over here not too long back.
Part of the reason I switched to 98 for my Starlet... Forester's always been
run on it.
Bigger outlay, but worth it IMO. Never had the Forester so much as hint at
pinging, engine running as smoothly as the day it was bought.... 52,000KM on
the clock now.

Starlet picks up a bit of extra power and fuel economy on 98 over say 95 or
91 octane. I reckon an extra 50-100km/tankful is well worth the outlay.

-mark

 

[Rick Courtright]

and text data is actually quite small and easy to store. Heck, it
wouldn't be hard to keep track of your acceleration, MPG for each fuel
fill, max speeds, ABS and traction control events, etc...

Hi,

My understanding is many trucking companies have been doing exactly that
for at least a dozen years! Stand on the brakes a bit hard cuz some
idiot cut the driver off, go a mile over the speed limit, take a catnap
after lunch and let the engine idle, then get called into the office for
a "chat" kinda stuff drove some of my driver-clients nuts!

Rick

 

[Rick Courtright]

What makes our gas 'crap' is ethanol and/or methyl tertiary butyl ether.

Hi,

I actually think it goes further back... I remember reading car rags in
the late '60's-early '70s that mentioned the US being listed as an
"inferior" fuel grade country by some German mfrs long before we spiked
our "punch" with ethanol or MTBE!

Rick

 

[Rick Courtright]

Gas here in GA is up to $2.25 for premium. Is mixing 50% 83 with 50% 93 ok
for a WRX ?

Hi,

I'd spring for the minimum grade called for in your owners' manual. If
the price differential between the lower and right grades of gas for the
engine's gonna break somebody, it's probably time they trade their WRX
for an econobox...

Rick

 

[hippo]

ether.


I actually think it goes further back... I remember reading car rags in
the late '60's-early '70s that mentioned the US being listed as an
"inferior" fuel grade country by some German mfrs long before we spiked
our "punch" with ethanol or MTBE!

Rick

Sounds reasonable. Oz fuels I use have the same RON whether 10% ethanol or
"straight" petrol - with whatever other additives the hand-on-heart ethanol
free brigade have instead! AFAIK 92RON unleaded works out about 93.5
equivalent in real life ping/knock resistance. Still won't use it in
stationary engines or fibreglass tank bikes though. No problems in 4
different cars or my old Suzuki 1100 over the last four years except for
an inital sacrificial fuel filter. Blending 83/93 still only gives you 88
on 50:50 though. I'd stick with premium for any sort of high stress
running - incl. stop/start. Cheers

 

[Reece Talley]

Here's my experience from Wednesday. Think about it and then you decide. We
drove my son's STi from LA to Phoenix to have it dyno-tuned at a particular
shop. It had had some mods done to it and needed a reflash as well. We
bought some gas in Blyth CA at a Union 76 station. It was labeled 91 octane.
On the dyno, the car would barely make 250 hp and it was very sensitive to
ping. Given the circumstances, we were advised to refuel with 5 gal of
Sunoco 100 octane and up to 9 gal of 91 octane. We did and the car now made
275 hp and the detonation problem was gone. On the way back to LA we filled
up at a Chevron station using their 91 octane. We've had no ping or rough
running since that refill. So, does the gas matter.....damn straight it
does. That crap we bough in Blyth was anything but 91 octane. The WRX and
the STi require premium gas...no exceptions. We have to pay $2.60 a gallon
for it out here in the People's Republik of Kalipornia. So, buck up me boy
and buy the good stuff. The alternative is some pretty heavy negative cash
flow after you screw up some pistons and valves.

 

[jabario]

You got a tank of bad gas. Taht's all. Water, contamination who knows?
Try good gas at 87 or 89 at let us know.

 

[Mystic]

Here's my experience from Wednesday. Think about it and then you decide. We
drove my son's STi from LA to Phoenix to have it dyno-tuned at a particular
shop. It had had some mods done to it and needed a reflash as well. We
bought some gas in Blyth CA at a Union 76 station. It was labeled 91 octane.
On the dyno, the car would barely make 250 hp and it was very sensitive to
ping. Given the circumstances, we were advised to refuel with 5 gal of
Sunoco 100 octane and up to 9 gal of 91 octane. We did and the car now made
275 hp and the detonation problem was gone. On the way back to LA we filled
up at a Chevron station using their 91 octane. We've had no ping or rough
running since that refill. So, does the gas matter.....damn straight it
does. That crap we bough in Blyth was anything but 91 octane. The WRX and
the STi require premium gas...no exceptions. We have to pay $2.60 a gallon
for it out here in the People's Republik of Kalipornia. So, buck up me boy
and buy the good stuff. The alternative is some pretty heavy negative cash
flow after you screw up some pistons and valves.

From my experience if you get gas from outside the state of California,
your engine will run much better. I fill up in Nevada when I am up
there and it makes a big difference in how the engine performs.

 

[Reece Talley]

I think this was black market gas. This was a small station right off the
highway and I suspect they ran it on a very thin margin. I should have known
better than to buy gas there. In Valencia where we live, I buy Shell,
Chevron or Exon and have had no trouble to date. The turbo at 17 lbs boost
is really cramming the air in that dinky little 4 banger. Add some heat and
if the octane isn't really 91 or better you get detonation.