Guys! With gas prices so high, I was forced to put 89 octone on my LS V8. It was one of those days when you forget your wallet and all you have in your pocket is $10. Anyway, the car is running like crap, I'm getting a knocking noise somewhat what a diesel engine noise makes. You guys know what I'm talking about. I refuled with 93 octane but its stil there. What do you guys suggest? would octane booster help?
knock..knock...
- Thread starter rrrick
- Start date
Quik LS
Dedicated LVC Member
rrrick said:
there is not much you can do until all the 89 is out. Once you think it's gone - undo the battery for 10mins - resetting the PCM.
02lsv8sport
Active LVC Member
rrrick said:
I have always used 89 octane in my 02 LS V8 without event the hint of a knock and good mileage and performance even with an ambient temperature of close to 100F. I will bet there is something else wrong with your car.
Quik LS
Dedicated LVC Member
we've talk about this 1000 times - do not put lower octane in your LS. Yes - it has knock sensors - but the engineers specifically told us that they did not design enough range within the PCM to adjust for the lower octane in all situations -- - - - - period.
you get less performance, less mileage, and risk damage to a $14k engine.
you get less performance, less mileage, and risk damage to a $14k engine.
itsnotmydaddys
Dedicated LVC Member
this may sound dumb, but whats the differenve in octane, and the diff levels in gas. i always put 93 in my ls but i never know whats the diff vetween them.
The higher the octane the slower gas will burn. The slower it burns the more you can compress it, hence more power. Our cars are high compression and require high octane. Lower octane gas can pre-ignite under compression (knock and ping). This is very bad for the engine over time. Our engines can adjust timing some to compensate (knock sensor) but not to 87 or 89.itsnotmydaddys said:
The reason that you can sometimes get lower octane and it works can depend on temperature, pressure, altitude, humidity etc. Also, some companies will fill both tanks with 93 and charge less for it if it comes out of the 91 tank.
Here is a more in-depth treatment of Octane: How Octane Works
Quik LS
Dedicated LVC Member
the LS uses as 10.55:1 compression and requires 91+ octane.
"The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting - compared to 93-octane.The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more. "
Think of knoking as the gas igniting before the piston is at the top of the engine - so the explosion wants to drive the piston back down - the wrong way. This doesn't actually happen but detonation harms an engine - to prevent this - engineers design the software in the PCM to retard the timing of the spark - waiting for the piston to move further in the cycle before firing.
it is possible that the cylinder pressure, intake charge heat and octane rating of the gas combines to make a mixture that is out of range for the PCM to adist for - meaning you will knock reguardless of the engine management system.
"The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting - compared to 93-octane.The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more. "
it is possible that the cylinder pressure, intake charge heat and octane rating of the gas combines to make a mixture that is out of range for the PCM to adist for - meaning you will knock reguardless of the engine management system.
Quik LS
Dedicated LVC Member
now that's funny - we both used the same article - within the same min - only I type soooooo slow...... 
Krib-Master
LVC Member
rrrick said:
So you got maybe .13 of a gallon more by using the lower octane (saved 30-40 cents), was it worth it? :bash:
Jim Henderson
Dedicated LVC Member
You got to use a lot of booster in most cases to have any effect. Read the fine print, usually says one can per 10 gallons for 1 point of boost. This means for our LS boosting from 87 to 91 would take 8 cans or ... 2 cans per tank for each point, times 4 points boost. Figuring a couple bucks per can at least, you are looking at $16 per tankful. At least for now, the difference between 91 and 87 price is low enough that the booster doesn't make any sense.
We can argue the merits of 87, 89, 91 all day but the cost of boost makes it no argument in favor of using boost for our cars. Buy the grade of gas that makes the LS perform the way you like. To be safe, use 91, it should always work unless you have a mechanical problem. I have successfully used 89 and unsatisfactorilly 87. I am still experimenting.
Good Luck,
Jim Henderson
We can argue the merits of 87, 89, 91 all day but the cost of boost makes it no argument in favor of using boost for our cars. Buy the grade of gas that makes the LS perform the way you like. To be safe, use 91, it should always work unless you have a mechanical problem. I have successfully used 89 and unsatisfactorilly 87. I am still experimenting.
Good Luck,
Jim Henderson
JES_LS
Dedicated LVC Member
As I listed on another thread here, My wife accidentally bought 16 gallons of 89 instead of 93. The car did not knock audibly, but drove like an absolute dog for the next three days (yeah I know thats a lot of driving). I had started to question her about what she had really bought and she told me that she hit the local amoco station and asked the India attendant for the "gold" grade of gas thinking that was the premium (which is silver at Amoco/BP stations). When I knew exactly what it was, I immediately added about 7 gallons of 93 octane to the tank to begin raising the general octane level and planned on adding in some injector cleaner when I got the car home. The LS straightened out on the drive home and has run fine ever since.
Now mind you I'm wondering if I should bother to reset the pcm's memory since we have done so much driving on the car already (I bought it in Dec and it had 11.8 K on it and now it has 25.4K miles). I'm figuring that we will push the car past 35K before 2006, but will have to wait and see with the gas prices and my job situation.
I just hope that the prices start to come back down soon or I'll have to start looking for more rims and tires for my motocycle soon. it is the only vehicle that I have ever owned that got 43mpg. And I have owned some small cars that were supposedly good on gas (yeah right!)
Now mind you I'm wondering if I should bother to reset the pcm's memory since we have done so much driving on the car already (I bought it in Dec and it had 11.8 K on it and now it has 25.4K miles). I'm figuring that we will push the car past 35K before 2006, but will have to wait and see with the gas prices and my job situation.
I just hope that the prices start to come back down soon or I'll have to start looking for more rims and tires for my motocycle soon. it is the only vehicle that I have ever owned that got 43mpg. And I have owned some small cars that were supposedly good on gas (yeah right!)
MsM8tress
Dedicated LVC Member
11 years driving a Mark VIII -
screw the fuel additives
if you cant afford 94octane,
either whore yourself or give your car to someone worthy. lolol
Notice the posts to this thread being low teens, and views being middle 200's! Cause were are all wondering what we will have to sacrafice in the upcoming weeks - be true to your Lincoln men.
MsM8tress
screw the fuel additives
if you cant afford 94octane,
either whore yourself or give your car to someone worthy. lolol
Notice the posts to this thread being low teens, and views being middle 200's! Cause were are all wondering what we will have to sacrafice in the upcoming weeks - be true to your Lincoln men.
MsM8tress
Learned lesson
I've always been faithful to my LS and put the 93 octane. Learned my lesson when I did'nt cause it ran like a wet dog. I thought my rattling knocking engine noise was from the low octane. I still have the problem, can't figure out what it is. It doesn't happen at startup, only when the cars been running a little while and only when I press on the gas from a complete stop. Anyone know what thid could be?
I've always been faithful to my LS and put the 93 octane. Learned my lesson when I did'nt cause it ran like a wet dog. I thought my rattling knocking engine noise was from the low octane. I still have the problem, can't figure out what it is. It doesn't happen at startup, only when the cars been running a little while and only when I press on the gas from a complete stop. Anyone know what thid could be?
hmmmmm... well, call me whatever you wish, but I just bought my '03 LS V8 and filled up a couple of days ago with 87 octane (i didn't bother to check what it needed, as I assumed, since it has similar power to a V6-powered car I just traded-in, it really didn't require high octane). I'd be willing to bet the dealer also filled it up with 87 before letting me drive away. The car has been running perfect and smooth with lots of power. I've been averaging between 23-24 mpg with mixed driving. Sooo... is this all bad? Should I really expect any problems? I guess I could try higher octane and see if my mileage improves.
Is anyone home????
Not to offend anyone but have you not read the information above from trained Lincoln techs regarding octane? Do you think Ford recommends 91+ because they have a vested interest in BP or Exxon? Personally I think someone would have to be nuts to put cheap fuel in an expensive to repair LS.
Not to offend anyone but have you not read the information above from trained Lincoln techs regarding octane? Do you think Ford recommends 91+ because they have a vested interest in BP or Exxon? Personally I think someone would have to be nuts to put cheap fuel in an expensive to repair LS.
KenRosier said:
Of course I've read it ... but how does that explain that my new-to-me LS is running absolutely perfectly fine on 87? What mileage are you guys getting running 93?
I actually mis-typed before ... I'm getting between 22-23 mpg.
Now that I know all this, I'll probably try 93 next fillup, but I'm still stumped how all these claims of doom and gloom amount to absolutely nothing in my real-world experience so far with the car.
keep in mind, it is on just its 2nd tank since I've had it ... but is it possible that the previous owner always ran regular in it, so it is somehow "used" to it? Of course, that doesn't jive with the fact that the car can't reduce its compression ratio ...
Qbrozen said:
2 things are happening. 1 is your engine is running in retarded (both in the auto sense and the human sense) timing mode. if you log pcm there is a spot to check this and I'd bet a shiny dime you are running retarded timing. the car still has power but not what it should. since you never put the right gas in you have nothing to compare it against. and keep in mind when you do go to 91+ it may take a couple hundred miles to adjust.
2.) catch it just right on a nice sunndyday and get heat soaked to the point where the pcm cannot retard the timing enough and you might become VERY sorry about running wrong octane. do you thing requiring premium fuel HELPS a car company sell cars? I'm of the belief if the car could make it on 87, they wouldn't require premium.
2.) guys premium gas is what $.15 center higher than regular? So that's about an extra $2.00 filling up your tank. If you are getting 400 miles between fillups and and drive 15,000 miles per year you are looking @ $75.00 per year extra by using premium vs. regular. That's assuming you don't get better gas mileage, too.
Without coming across ignorant, if $75.00 a year is a problem, you bought the wrong car.
02lsv8sport
Active LVC Member
Qbrozen said:
If your car does not knock and performs up to your expectations with 87 octane why pay 20 cents more per gallon than needed. It is hard to believe you are getting 22 mpg; my 2002 V8 maybe gets 19 mpg mixed using 89 octane.
Ford only recommends 91+ octane not requires it. If I was racing I might use 91+ but your car has knock sensors and a computer to adjust to most any reasonable octane.
For those who thinks that using lower octane will cause the spark to be highly retarded, I have not found that to be true. I have a scanner that records real time data on among other things timing advance. In monitoring my LS with 89 octane fuel I found the advance was what my Shop Manual showed to be normal for my LS. So I did not see a retarded spark using 89 octane.
02lsv8sport said:
of course, everyone's driving habits are different. My mixed conditions commute is approximately 8 miles city and 26 miles highway. Plus, I have been driving VERY light with a keen eye on the mileage computer due to current prices at the pump. I've only smoked the tires once so far.