Check engine light and Chevron gasoline in 96 Avalon

i wanted to get this on the record to help others possibly save money,
and hear if anyone else has experienced this same non-intuitive
behavior.

My 1996 Avalon, 170K miles, had its check engine light appear (first
time ever) two weeks ago. Diagnostic showed an oxygen sensor problem.
A couple days later the light went out. (Happy day.)

This check engine light went on again five days ago, maybe 25 miles
after a fillup of California Chevron regular fuel. Then I realized I
had filled up with Chevron (different station) the first time, and it
went out after the next fillup. I rarely buy Chevron, though they have
a fine reputation.......

Both times the light went off after the next fillup, with Arco, my
normal gas.

Any theories about the relationship of Chevron's blend to problems???
Anyone else experience this???

I dont think it is gas. Considering you have 170K miles on it and never
had a CEL its just normal wear and tear. Oxygen sensor is what mostly
causes the problem and I think just replacing it would solve your
problem.

However I do have doubts over quality of gas. My mechenic recommends I
use higher quality gas like 91 even though my camry can take 87. I dont
kow how much it really affects the peoformance of the car and life of
engine. May be someone can shed some light on it. Thanks....

John from Oakland wrote:[color=blue]
> This check engine light went on again five days ago, maybe 25 miles
> after a fillup of California Chevron regular fuel.[/color]

I've read that immediately after a big tanker fills the
gas station's underground tanks that sediment is stirred up
and can result in a problem similar to what you described.
I wonder if that is true, and if it is, how big an effect it is.

[email]learnfpga@gmail.com[/email] wrote:[color=blue]
> I dont think it is gas. Considering you have 170K miles on it and never
> had a CEL its just normal wear and tear. Oxygen sensor is what mostly
> causes the problem and I think just replacing it would solve your
> problem.[/color]
[color=blue]
> However I do have doubts over quality of gas. My mechenic recommends I
> use higher quality gas like 91 even though my camry can take 87. I dont
> kow how much it really affects the peoformance of the car and life of
> engine. May be someone can shed some light on it. Thanks....[/color]

If the owners manual calls for 87 and its not pinging run 87. 91 will get
you nothing but a higher bill at the pump.

[url]http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm[/url]

In article <1144938466.694318.68220@i39g2000cwa.googlegroups.com>,
[email]learnfpga@gmail.com[/email] wrote:
[color=blue]
> However I do have doubts over quality of gas. My mechenic recommends I
> use higher quality gas like 91 even though my camry can take 87. I dont
> kow how much it really affects the peoformance of the car and life of
> engine. May be someone can shed some light on it. Thanks....[/color]

The octane rating of gasoline has nothing to do with "quality." It is
simply a measure the gasoline's ability to resist detonation (where the
fuel/air mixture burns explosively due to heat and pressure in the
combustion chamber, rather than the normal combustion initiated by the
spark plug). Engines are designed to run a certain combustion chamber
temperatures and pressures and that is what determines the octane rating
needed. Buying a higher octane gasoline than the owner's manual calls for
provides no benefits and is simply a waste of money.

Merritt

"John from Oakland" <cautiousoptimist@gmail.com> wrote in message
news:1144911225.472270.44750@t31g2000cwb.googlegroups.com...[color=blue]
>i wanted to get this on the record to help others possibly save money,
> and hear if anyone else has experienced this same non-intuitive
> behavior.
>
> My 1996 Avalon, 170K miles, had its check engine light appear (first
> time ever) two weeks ago. Diagnostic showed an oxygen sensor problem.
> A couple days later the light went out. (Happy day.)
>
> This check engine light went on again five days ago, maybe 25 miles
> after a fillup of California Chevron regular fuel. Then I realized I
> had filled up with Chevron (different station) the first time, and it
> went out after the next fillup. I rarely buy Chevron, though they have
> a fine reputation.......
>
> Both times the light went off after the next fillup, with Arco, my
> normal gas.
>
> Any theories about the relationship of Chevron's blend to problems???
> Anyone else experience this???
>[/color]

It is probably a coincidence. Rather than take action based on uninformed
speculation, you should pull the codes stored in the computer, report them
here, and then perhaps someone can make a more informed guess as to what the
cause may be.
--

Ray O
(correct punctuation to reply)

<learnfpga@gmail.com> wrote in message
news:1144938466.694318.68220@i39g2000cwa.googlegroups.com...[color=blue]
>I dont think it is gas. Considering you have 170K miles on it and never
> had a CEL its just normal wear and tear. Oxygen sensor is what mostly
> causes the problem and I think just replacing it would solve your
> problem.
>
> However I do have doubts over quality of gas. My mechenic recommends I
> use higher quality gas like 91 even though my camry can take 87. I dont
> kow how much it really affects the peoformance of the car and life of
> engine. May be someone can shed some light on it. Thanks....
>[/color]

As several people have posted, if the engine is not pinging on hard
acceleration, higher octane gas than recommended by the factory is a waste
of money. If the vehicle's ignition will advance enough to take advantage
of the higher octane or is a higher compression engine, then the higher
octane fuel will have a benefit.

Rather than take your car to a mechanic, I recommend that you take it to an
ASE certified technician at least, or if you want to take it to someone who
is most familiar with your Toyota, take it to a Toyota Master Diagnostic
Technician.
--

Ray O
(correct punctuation to reply)

"ll" <lkslittle@REMOVEcomcastTHIS.net> wrote in message
news:443E77E4.D328C511@REMOVEcomcastTHIS.net...[color=blue]
> John from Oakland wrote:[color=green]
>> This check engine light went on again five days ago, maybe 25 miles
>> after a fillup of California Chevron regular fuel.[/color]
>
> I've read that immediately after a big tanker fills the
> gas station's underground tanks that sediment is stirred up
> and can result in a problem similar to what you described.
> I wonder if that is true, and if it is, how big an effect it is.[/color]

While it is possible that sediment in a gas station's storage tank may be
stirred up immediately after being filled, the vehicle's fuel filter should
trap it before it gets to the engine. Some gas stations have filters on
their pumps.

You should purchase fuel from a gas station that sells a large quantity so
that the sediment and water do not have a chance to accumulate. It is not
uncommon for some gas stations to get daily deliveries of 8,000 to 10,000
gallons.
--

Ray O
(correct punctuation to reply)

Merritt Mullen <mmullen8014@mchsi.com> wrote:
[color=blue]
>In article <1144938466.694318.68220@i39g2000cwa.googlegroups.com>,
> [email]learnfpga@gmail.com[/email] wrote:
>[color=green]
>> However I do have doubts over quality of gas. My mechenic recommends I
>> use higher quality gas like 91 even though my camry can take 87. I dont
>> kow how much it really affects the peoformance of the car and life of
>> engine. May be someone can shed some light on it. Thanks....[/color]
>
>The octane rating of gasoline has nothing to do with "quality." It is
>simply a measure the gasoline's ability to resist detonation (where the
>fuel/air mixture burns explosively due to heat and pressure in the
>combustion chamber, rather than the normal combustion initiated by the
>spark plug). Engines are designed to run a certain combustion chamber
>temperatures and pressures and that is what determines the octane rating
>needed. Buying a higher octane gasoline than the owner's manual calls for
>provides no benefits and is simply a waste of money.
>
>Merritt[/color]

Exactly and precisely...while I have very little experience with
the technical aspects of automobile engines I have a great deal
of technial training and experience with large aircraft piston
engines and can vouch for Merritt's statements...I inadvertently
ruined a $150,000 aircraft engine in about 5 seconds once because
I missed noticing that the 'derichment valve' hadn't returned to
normal after takeoff when the 'water injection' was shut off and
the engine beat itself to death with heavy detonation.

I was interested and looked up the overhaul strip report on that
engine...almost all of the 18 pistons were holed, some of the
valves were 'headless' and some of the cylinder heads themselves
were split open...gives one a good idea just how destructive
heavy detonation can be...

I understand that modern automobile engines are protected with
'fancy pants' systems like 'knock sensors' etc now and these
engines in normal circumstances aren't stressed like aircraft and
race car engines anyway so detonation isn't nearly the concern
now but it certainly isn't something to toss off lightly either.
--

-Gord.
(use gordon in email)

"John from Oakland" <cautiousoptimist@gmail.com> wrote in message
news:1144911225.472270.44750@t31g2000cwb.googlegroups.com...[color=blue]
>i wanted to get this on the record to help others possibly save money,
> and hear if anyone else has experienced this same non-intuitive
> behavior.
>
> My 1996 Avalon, 170K miles, had its check engine light appear (first
> time ever) two weeks ago. Diagnostic showed an oxygen sensor problem.
> A couple days later the light went out. (Happy day.)
>
> This check engine light went on again five days ago, maybe 25 miles
> after a fillup of California Chevron regular fuel. Then I realized I
> had filled up with Chevron (different station) the first time, and it
> went out after the next fillup. I rarely buy Chevron, though they have
> a fine reputation.......
>
> Both times the light went off after the next fillup, with Arco, my
> normal gas.
>
> Any theories about the relationship of Chevron's blend to problems???
> Anyone else experience this???
>[/color]

My theory is that there is no relationship at all. I further theorize you
need a new O2 sensor. Just my theory though, your theory may vary.

<learnfpga@gmail.com> wrote in message
news:1144938466.694318.68220@i39g2000cwa.googlegroups.com...[color=blue]
>I dont think it is gas. Considering you have 170K miles on it and never
> had a CEL its just normal wear and tear. Oxygen sensor is what mostly
> causes the problem and I think just replacing it would solve your
> problem.
>
> However I do have doubts over quality of gas. My mechenic recommends I
> use higher quality gas like 91 even though my camry can take 87. I dont
> kow how much it really affects the peoformance of the car and life of
> engine. May be someone can shed some light on it. Thanks....
>[/color]

You are throwing money away if you are in the habit of buying a higher grade
fuel than is needed. The ONLY function of high octane is to prevent
pre-ignition that comes from heat, compression, and/or advanced timing (or
combinations of these maladies), or the normal function of a high
performance motor. If your car can run on regular without pinging (pre
ignition) typicaly heard under load and climbing hills at speed, then you do
not need high octane fuel. Since most Toyota motors are not high compression
engines, they do not need high octane gas. Your mechanic is telling you to
use fuel that you do not need to use.

Having said that, IF you need to use high octane gas, then you are having
problems that the premium fuel is masking, or you have a Toyota model with a
high performance engine.

"Jeff Strickland" <crwlr@yahoo.com> wrote:

snip
[color=blue]
>
>You are throwing money away if you are in the habit of buying a higher grade
>fuel than is needed. The ONLY function of high octane is to prevent
>pre-ignition that comes from heat, compression, and/or advanced timing (or
>combinations of these maladies), or the normal function of a high
>performance motor. If your car can run on regular without pinging (pre
>ignition) typicaly heard under load and climbing hills at speed, then you do
>not need high octane fuel. Since most Toyota motors are not high compression
>engines, they do not need high octane gas. Your mechanic is telling you to
>use fuel that you do not need to use.
>
>Having said that, IF you need to use high octane gas, then you are having
>problems that the premium fuel is masking, or you have a Toyota model with a
>high performance engine.
>
>[/color]
Exactly right in all respects 'except' you're labeling 'ping' as
'preignition' and it isn't...ping is detonation (it occurs
'after' the normal ignition event...

'Preignition' is where the fuel/air charge is ignited 'before'
the normal ignition point and is much deadlier...

Just remember that 'preignition' and 'detonation' are two
separate, distinct and different occurrences...
--

-Gord.
(use gordon in email)

ll <lkslittle@REMOVEcomcastTHIS.net> wrote:
[color=blue]
>I've read that immediately after a big tanker fills the
>gas station's underground tanks that sediment is stirred up
>and can result in a problem similar to what you described.
>I wonder if that is true, and if it is, how big an effect it is.[/color]

My son (a Shell Oil Co engineer) told me a really interesting
problem that this local gas station had a few years ago...they'd
dip their tanks (with those long wooden dipsticks of course) and
find that they'd need XXX gallons of fuel...the tanker'd come and
pump 'that' many gallons and stop.

The driver'd dip the tank and find that the dip showed the fuel
level about 300 gallons short, yet the tank was full. He'd
scratch his head, tell the station owner about it. Station owner
would check the dip the next day and would come up with the
correct amount

This went on for awhile...nobody could figure what was going on.
Shell Oil told my son to 'fix it', took him awhile but eventually
he got it.

What was happening was that there was about 300 gallons of water
in the bottom of the tank which would be liquid under normal
circumstances but when it was being refilled with super cold fuel
from the tanker would freeze and hold the dipstick up ~300
gallons from the bottom. (I don't use Shell any more)
--

-Gord.
(use gordon in email)

And I don't believe the story ;)

mike hunt

"Gord Beaman" <gord@islandtelecom.com> wrote in message
news:qdj2425fu2c9133va3rs1u8jbskdd5kp87@4ax.com...[color=blue]
> ll <lkslittle@REMOVEcomcastTHIS.net> wrote:
>[color=green]
>>I've read that immediately after a big tanker fills the
>>gas station's underground tanks that sediment is stirred up
>>and can result in a problem similar to what you described.
>>I wonder if that is true, and if it is, how big an effect it is.[/color]
>
> My son (a Shell Oil Co engineer) told me a really interesting
> problem that this local gas station had a few years ago...they'd
> dip their tanks (with those long wooden dipsticks of course) and
> find that they'd need XXX gallons of fuel...the tanker'd come and
> pump 'that' many gallons and stop.
>
> The driver'd dip the tank and find that the dip showed the fuel
> level about 300 gallons short, yet the tank was full. He'd
> scratch his head, tell the station owner about it. Station owner
> would check the dip the next day and would come up with the
> correct amount
>
> This went on for awhile...nobody could figure what was going on.
> Shell Oil told my son to 'fix it', took him awhile but eventually
> he got it.
>
> What was happening was that there was about 300 gallons of water
> in the bottom of the tank which would be liquid under normal
> circumstances but when it was being refilled with super cold fuel
> from the tanker would freeze and hold the dipstick up ~300
> gallons from the bottom. (I don't use Shell any more)
> --
>
> -Gord.
> (use gordon in email)[/color]