89 Octane runs terrible in truck

[mechtech2]

Something is WAY backwards.
Let's start with engine knock with a HIGHER octane fuel!
Absolutely the opposite of what should happen.
Maybe it's that particular gas station.


You will NOT get "incomplete combustion" from using a higher octane fuel than necessary. You will only increase your costs.

 

[Highline9]

you got a bad tank of fuel, not the octane. when it runs out change that fuel filter.

 

[CROWNVIC4LIFE]

Originally Posted By: Whimsey
Here in NJ we're stuck with 10% ethanol in all grades. Recently 89 octane is now over 20 cents a gallon more than 87 octane.Whimsey


Same thing here in Miami.

 

[Eddie]

All grades here in Cape Coral Fl has up-to-10% ethanol. On rare occasions I see 89 cheaper than 87 and it happens when 89 is not selling and they have more 89 being tanked in, so the price drops under 87 for a few days only. The origonator of this topic has me confused or is he confused or is the gas contaninated at the station or?

 

[volk06]

The 89 Octane in Iowa has E10, thats why its cheap than 87 octane. 87 is usually 10cents more expensive but contains no E10. 89 is the only fuel great with E10 unless you get a blender station with E15, E30, E85. 87 and 91 is usually free of E10 but it is dependent on the gas station.

 

[addyguy]

Up here, there is a chain of stations that sells regulat 87 at the exact same price as 89 made w/10% ethanol.

I usually get the 89, and it seems to make no difference to my vehicle what I run.

 

[Boss302fan]

Something else is going on because 87/89 should not make any difference... I would check out your fuel system/filter and plugs. Have you changed the plugs?

You are talking about the 04 F150 with 106K miles, right?

 

[StarInspector]

I use the Nuetra and it helps with the ethanol, No issues here anymore no matter where or what I use on fuel

 

[MNgopher]

Iowa does indeed have slightly different gas pricing than just about anywhere else (though I have seen the same thing in parts of Nebraska in the past). Gotta watch what you are pumping!

Are you running into this issue with 89 from multiple stations? Or just from one? If its from one station, I'd try buying 89 somewhere else. For a long time, I owned one car that pinged on Amoco gasoline (which was sourced from a different refinery at the time). None of my other cars had a problem with it, just the one. Changed gas stations and no more problems.

 

[Phil_G]

Originally Posted By: Highline9
you got a bad tank of fuel, not the octane. when it runs out change that fuel filter.


I agree. It sounds like the OP only filled it once.

 

[lexus114]

Originally Posted By: dparm
You should run the octane the manufacturer specifies.

Octane is a measurement of resistance to detonation. 93 octane is harder to detonate than 89 octane; some motors need this higher resistance because they are higher compression and early ignition would rob them of power.

Your truck, on the other hand, can't fully detonate anything above 87. That's why it runs rough and the gas mileage drops: incomplete combustion.

Or recommends,such as my owners manual. "For improved vehicle performance, the use of 91 octane or higher is recommended." Honestly, it should really read..."Premium unleaded fuel only". Because when I use 87, or 89 octane it runs terrible.

 

[cutter]

The "harder to detonate" high octane gas means it resists compression better, so it won't prematurely detonate when squeezed. Once a spark is introduced, it will burn the same as any grade.

 

[Brigadier]

I do not understand how anyone can think that an engined 'spec'd for 87 octane gas' will run worse on 89 or 91/92/93 octane. Can someone explain this to me?

I was taught when I worked in a service bay at a dealership that the computers are ALWAYs advancing the timing until detonation starts to occur, hence the inclusion of knock sensors. The knock sensor tells the computer to back off the timing. It is a constant tug of war between the two. So, if you put in 89 or 92 octane gas, then the onset of the knock sensor will be delayed, and the computer will be able to advance the timing further before that happens. Has this changed recently?

And if you read the posts carefully, Iowa only has ethanol in the 89 grade, so his 87 and 92 are pure gas[strange for the corn state]. This is why it is knocking on the 89.

 

[Brigadier]

http://wiki.answers.com/Q/What_does_a_knock_sensor_do

So logic dictates that a higher octane fuel will allow the ECM to advance the timing further before the knock sensor tells it to back off. The more advance the timing, the more power and fuel economy.

 

[Spazdog]

I experimented with a couple of tanks of 93 in the Mazda. Overall fuel economy went down and my highly calibrated and scientific butt-dyno did not notice any real difference.

Using anything less than 93 in the PT Cruiser will result in knocking and pinging under boost. 89 did not work. I didn't even try 87

 

[Gene K]

Originally Posted By: Brigadier
http://wiki.answers.com/Q/What_does_a_knock_sensor_do

So logic dictates that a higher octane fuel will allow the ECM to advance the timing further before the knock sensor tells it to back off. The more advance the timing, the more power and fuel economy.



The spark map in the factory ECM has a maximum. In most engines the maximum is tuned for recommended fuel.This is why you can often pick up 5-15 bhp tuning the spark tables in the factory ECM mapping. They dont want an engine constantly entering detonation trying to advance timing.

While in fact Ive yet to see a production engine tuned for 87 make less power on 93 than 87 the gain is often only 1-3 bhp. I have seen an engine lose power on 100 octane.

The reason is flame travel speed. The cheap high octane fuel generally has slower flame travel speed than the lower octane fuel. Do not fall in the trap of thinking all high octane fuel has slow flame travel speeds though. This is not always the case as fuel such as that used in Formula One Motorcycles have very fast flame travel speeds despite high octane. It was around $60 a gallon a decade ago. I have no idea what it cost today.

 

[Gene K]

To OP:

Your engine is running to lean on the 89 octane E10 due to the ethanol.

 

[SteveSRT8]

^^^^ sorry Gene but if his truck is running correctly the feedback loop from the O2 sensor will adjust the mixture appropriately. Can't run lean.

And the bit about high octane giving poor quality combustion is correct, despite what others have said.

If you do not have the compression and spark advance for higher octane you ARE experiencing incomplete combustion and loss of power in most cases.

 

[Spazdog]

Originally Posted By: Gene K

While in fact Ive yet to see a production engine tuned for 87 make less power on 93 than 87 the gain is often only 1-3 bhp. I have seen an engine lose power on 100 octane.


I can attest to that.

When I was younger, I filled up at a "Superfuel" station. I forget the exact octane but it was over 100. (it was blue and evaporated quickly)

This was at a time when the Mustang GT 5.0 had a 9.0:1 C/R. My bike had an 11:1 compression ratio and had a Factory Pro Ignition advance kit. Surely if these Mustang guys are running this 100+ octane fuel, my Kawasaki will really respond to it.

Nope.

It would start and idle but would stumble and barely run at full throttle. GS500s were dogging me.

 

[mechtech2]

spaz -
That was one instance with who knows what fuel.
Really.