Octane!

[tbone]

Lately I've been putting 87 octane in my MM because I'm trying to save a few bucks when I can. I never notice any difference whatsoever in the performance, and in particular I hear no pinging from the motor, and believe me, I listen closely (for obvious reasons.)

Any observations from the peanut gallery on this?

[FordNut]

My wife did it for about 60 k miles. Then it developed a little detonation coming of idle. Got it de-carboned at the dealer, I think they used something from BG. Been running premium ever since, 165k and no rattles. Take your chances.

[MM03MOK]

You have an aftermarket tune. What octane is the tune set for? If you're tuned for 87, there shouldn't be an issue.

If your tune is for 93 octane, you're not running efficiently and may be compromising your car. For all you have invested in the car, it's not worth saving 20-30 cents a gallon if it may lead to engine or ignition problems. Just because you don't hear it, doesn't mean it's not happening to a lesser degree. Go a little easier on the gas pedal if you want to save a little money and increase your mpg.

[tbone]

You are saying that lesser octane gas causes carbon buildup?

[tbone]

You have an aftermarket tune. What octane is the tune set for? If you're tuned for 87, there shouldn't be an issue.

If your tune is for 93 octane, you're not running efficiently and may be compromising your car. For all you have invested in the car, it's not worth saving 20-30 cents a gallon if it may lead to engine or ignition problems. Just because you don't hear it, doesn't mean it's not happening to a lesser degree.

Set for 93. I thought if you don't hear it, not an issue.(?)

Money is an issue right now. What can I say?

That's why I'm asking.

[MOTOWN]

i tried 87 octane a few times it was like i never got gas it burned so quick not to mention performance suffered, not worth the trouble imo

[FordNut]

Just relating my experience. I can't corrrelate it to brand, because in both cases we used the cheapest available. Usually Murphy/Wal-mart. Only difference was regular vs premium.

[tbone]

Just relating my experience. I can't corrrelate it to brand, because in both cases we used the cheapest available. Usually Murphy/Wal-mart. Only difference was regular vs premium.

Did your wife go WOT often during the 60K?

[FordNut]

NEVER in either case. I seriously doubt that car has ever seen WOT.

[tbone]

NEVER in either case. I seriously doubt that car has ever seen WOT.

That can cause carbon build up. A nice thrashing once in a while is good to clean out a motor.

[FordNut]

Like I said, same driving habits on the 87 octane and 93 octane. Got carbon buildup in 60k on the 87 octane and it's been over 100k on the 93 octane with no problems. Read into it what you want to, I'll keep running 93.

[tbone]

Like I said, same driving habits on the 87 octane and 93 octane. Got carbon buildup in 60k on the 87 octane and it's been over 100k on the 93 octane with no problems. Read into it what you want to, I'll keep running 93.

But if an occasional WOT during use of lesser fuels alleviates the problem of carbon buildup, your point is not valid. Most men I know drive the Marauder quite aggressively.......

[FordNut]

I am not making any points, just stating the facts as they occurred. You are making assumptions as to how it MIGHT have turned out differently under other conditions.

Your car, do what you want to. I'll stick with premium. I have two Marauders and have put about 285k miles combined on them so I figure that's enough experience to provide an educated answer to your original post.

[FordNut]

Actually, 87 octane is perfect for your car. The tuner who sold you a 93 octane tune was clueless, it doesn't matter what octane you run. Kerosene is ok, too.

[tbone]

I am not making any points, just stating the facts as they occurred. You are making assumptions as to how it MIGHT have turned out differently under other conditions.

Your car, do what you want to. I'll stick with premium. I have two Marauders and have put about 285k miles combined on them so I figure that's enough experience to provide an educated answer to your original post.

Why are you getting testy? You say your wife drove the car for 60k with carbon buildup. I just think that contributed to it.

[tbone]

Actually, 87 octane is perfect for your car. The tuner who sold you a 93 octane tune was clueless, it doesn't matter what octane you run. Kerosene is ok, too.

Nice response.
Have a nice Christmas!

[tbone]

Actually, 87 octane is perfect for your car. The tuner who sold you a 93 octane tune was clueless, it doesn't matter what octane you run. Kerosene is ok, too.

And a Happy New Year!:)

[RR|Suki]

high compression v8 + 87 octane + 93 octane tune = trouble waiting in the wings, knock sensor might be the only thing saving you, and I wouldn't call it fool proof. PS it is not true that just because you personally can't hear any detonation then there's no problem.

[MM03MOK]

Why are you getting testy? You say your wife drove the car for 60k with carbon buildup. I just think that contributed to it.


Like I said, same driving habits on the 87 octane and 93 octane. Got carbon buildup in 60k on the 87 octane and it's been over 100k on the 93 octane with no problems. Read into it what you want to, I'll keep running 93.

Maybe this is easier to understand:



same driving habits on the 87 octane and 93 octane
Got carbon build-up in 60k on the 87 octane
100k on the 93 octane with no problems (no carbon build-up)

The variable is the octane, not the driving habits.

http://www.godsowncounty.co.uk/wp-content/uploads/2009/05/peanuts-in-shells.jpg

[FordNut]

Actually my first post in this thread should have been "what answer do you want to hear, so I can provide that answer for you". Obviously an educated answer wasn't what you wanted to hear, only some confirmation that you're ok doing what you wanted to do.

[tbone]

high compression v8 + 87 octane + 93 octane tune = trouble waiting in the wings, knock sensor might be the only thing saving you, and I wouldn't call it fool proof. PS it is not true that just because you personally can't hear any detonation then there's no problem.

You are probably right. I guess I just wanted to hear someone say it. The knock sensor is a good thing, but not something to rely on. I remember my dad's "77 Olds 98 with a 350 4 barrel. It would knock like crazy until I told him to put premium in it. Boy was he ever happy after that! That car was fast for a '77. It was a blast to drive.

[FordNut]

Maybe this is easier to understand:



same driving habits on the 87 octane and 93 octane
Got carbon build-up in 60k on the 87 octane
100k on the 93 octane with no problems (no carbon build-up)

The variable is the octane, not the driving habits.

http://www.godsowncounty.co.uk/wp-content/uploads/2009/05/peanuts-in-shells.jpg

Thank you Mary.

[tbone]

Maybe this is easier to understand:



same driving habits on the 87 octane and 93 octane
Got carbon build-up in 60k on the 87 octane
100k on the 93 octane with no problems (no carbon build-up)
The variable is the octane, not the driving habits.

http://www.godsowncounty.co.uk/wp-content/uploads/2009/05/peanuts-in-shells.jpg

If an occasional WOT with 87 octane serves the purpose of driving off the carbon vs. wimpy driving with 93 octane and no carbon was my point.

Jeez.

[tbone]

You guys love to be "right" and sarcastic. Congrats.

[FordNut]

If an occasional WOT with 87 octane serves the purpose of driving off the carbon vs. wimpy driving with 93 octane and no carbon was my point.

Jeez.

I propose you perform the experiment and let us know in 60k. If it still runs.

[tbone]

I propose you perform the experiment and let us know in 60k. If it still runs.

Well, your wife's POS still ran, didn't it?:flamer:

[MM03MOK]

You guys love to be "right" and sarcastic. Congrats.
Look....you asked for input...you got input. Brian is one of the most experienced owners here and he's giving you his first-hand knowledge. Don't diss him because you didn't like his answer.

It's your car. You can do whatever you like with it. I hope your work situation turns around.

[FordNut]

Well, your wife's POS still ran, didn't it?:flamer:

Yes, it has a VERY conservative, totally stock tune that is factory rated for 91 octane. You have an aggressive aftermarket tune that is rated for 93 octane. I reported real world results. Please repeat the experiment using your test protocol.

[MrBluGruv]

Frankly, with the cost difference between 87 and 93 (at least around here anyways), I don't see why you'd skimp out.

I used to argue that it's not the difference between octane ratings that's the killer, it's the base cost of gas, and here's how I proved it: Around here at least (which is probably cheaper for all octane ratings, but I imagine the cost spread between ratings is the same), 87 is going for about $2.61 and 93 is going for about $2.89 or $2.90. If you were to fill the entire 21 gallon tank each stop, you'd pay $54.81 for 87 and $60.90 for 93. if you averaged 18mpg, and drove no more than 378 miles a week (this would put you at ZERO gas at the start of every fillup), you'd be saving $24.36 a month roughly.

Now by no means do I mean to insult you or belittle your situation if times are really that tough, but is it really worth $24 a month to use something you can't be reasonably sure about, especially when you could be talking about the reliability and longevity of something as important as an MM?

Of course my math is not as valid if 93 is considerably more expensive than 87, or if you put significant mileage on your MM per week, cause then that number will definitely inflate per month.

[tbone]

But if an occasional WOT during use of lesser fuels alleviates the problem of carbon buildup, your point is not valid. Most men I know drive the Marauder quite aggressively.......


This is where the thread apparently got off track. I did not say this to be disrespectlful. I was trying to say that a woman driving the car in a wimpy fashion can cause the carbon buildup, regardless of the fuel used. I could have worded it better.

But I also think that you guys could let your guard down a little and be a little less aggressive in your points. I know you are very experienced in cars, but you don't have to drive it home with a steel spike.

[tbone]

Frankly, with the cost difference between 87 and 93 (at least around here anyways), I don't see why you'd skimp out.

I used to argue that it's not the difference between octane ratings that's the killer, it's the base cost of gas, and here's how I proved it: Around here at least (which is probably cheaper for all octane ratings, but I imagine the cost spread between ratings is the same), 87 is going for about $2.61 and 93 is going for about $2.89 or $2.90. If you were to fill the entire 21 gallon tank each stop, you'd pay $54.81 for 87 and $60.90 for 93. if you averaged 18mpg, and drove no more than 378 miles a week (this would put you at ZERO gas at the start of every fillup), you'd be saving $24.36 a month roughly.

Now by no means do I mean to insult you or belittle your situation if times are really that tough, but is it really worth $24 a month to use something you can't be reasonably sure about, especially when you could be talking about the reliability and longevity of something as important as an MM?

Of course my math is not as valid if 93 is considerably more expensive than 87, or if you put significant mileage on your MM per week, cause then that number will definitely inflate per month.

You're right.

[FordNut]

This is where the thread apparently got off track. I did not say this to be disrespectlful. I was trying to say that a woman driving the car in a wimpy fashion can cause the carbon buildup, regardless of the fuel used. I could have worded it better.

But I also think that you guys could let your guard down a little and be a little less aggressive in your points. I know you are very experienced in cars, but you don't have to drive it home with a steel spike.

I understand what you're saying, but the same wimpy woman driving the same car the same way with the same brands of gas and the same tune has gone over 100k on 93 octane with no carbon buildup. With 87 octane she had carbon buildup in 60k. The ONLY variable is the octane rating.

The only conclusion I can draw from this 165k experiment is this:
87 octane = carbon deposits buildup in 60k
93 octane = no carbon deposits buidup in 105k

[MM03MOK]

Just because someone doesn't drive WOT doesn't mean they drive the car in a "wimpy fashion," female or male. For clarity's sake read the whole thread again. Brian said there was no build-up when using 93 octane and using your words, "a woman driving the car in a wimpy fashion."

FYI - I also own two Marauders and I'm a woman to boot! :D

-30-

[tbone]

Just because someone doesn't drive WOT doesn't mean they drive the car in a "wimpy fashion," female or male. For clarity's sake read the whole thread again. Brian said there was no build-up when using 93 octane and using your words, "a woman driving the car in a wimpy fashion."

FYI - I also own two Marauders and I'm a woman to boot! :D

-30-

1. Many women never floor a car, or very rarely, which helps remove carbon. Wimpy imho.
2. I never said there was buildup with 93 octane, so not sure where you are going with that.......
3. Never argue with an administrator.:D

[TFB]

Well lessee... Since higher octane fuel burns slower than lower octane, in theory a "babied" engine should have more carbon build up on the premium but since the higher octane does usually eliminate pinging, carbon buildup may not be noticed...

[tbone]

Yes, it has a VERY conservative, totally stock tune that is factory rated for 91 octane. You have an aggressive aftermarket tune that is rated for 93 octane. I reported real world results. Please repeat the experiment using your test protocol.

I have a test protocol for you as well.

PM me for instructions.

[Motorhead350]

If you are trying to save a few bucks eat less and keep the 93 going. Believe me I have done it!

[justbob]

Lets lighten up, i'll start.

Melanie wants me to teach her how to brake torque next spring :) This brought a tear to my eyes.

[Bradley G]

Well documented cases of people ignoring the "Required" label on the inside of the fuel door and has had catastrophic results.
While I was at Lonnie @ Blue Oval Chips shop, I was intrusted with Lonnies' personal vehicle a 1998 Lincoln T/C Cartier to fetch parts for my blower upgrade.
The car requires premium fuel on top of an already aggressive spark advance in his tune .
I went to a station between the Napa and his house and the only carried 87 & 89.
I just put the 87 in not noticing the sticker on the fuel door OOOPS!!!.
He calls me the following week appreciating the jesture but complaining of terrible detonation on his Lincoln.
He follows with, "did you put regular unleaded in my car?", "MMMM?,... Yea" I torted.
"That explains it!" He followed.
It meant enough to him to retune the car or put an additive of octane boost in the tank to curb the pinging.
These motors are/can be weak when we push them to thier limits.
I have used 87 a couple times but I tried to keep that in mind when driving.
Like has been said, on a full tank , on all 19 gallons the difference between 87 & 93 is a few bucks .

[J-MAN]

Peace on earth. Good will towards men. Women too!

[FordNut]

This thread reminds me of the people on here who ask about driveshaft vibration, ignore the advice they get, then start a thread a few weeks later about a cracked tranny housing and fluid sprayed all over the underside of the car. :lol:

[FordNut]

Well lessee... Since higher octane fuel burns slower than lower octane, in theory a "babied" engine should have more carbon build up on the premium but since the higher octane does usually eliminate pinging, carbon buildup may not be noticed...

Actually, when the car developed the pinging I tried switching to 93 octane first. It still had the pinging. After having it "de-carboned" it was ok.

The money saved by running 87 octane was maybe enough to have it de-carboned.

[Bluerauder]

Lately I've been putting 87 octane in my MM because I'm trying to save a few bucks when I can.

The owner's manual says 91 Octane as a minimum. You are now tuned for 93 Octane. You are gambling with your engine. Your call; but others here have recommended against it. Ignore that advice at your own peril. Just not worth the minimal savings in the per gallon price difference between 87 and 93. You will never be able to drive your car far enough on the cheaper gas to offset the cost of replacing the engine. Occasional "romps" at WOT and cheap gas just increase your odds of a catastrophic failure. Good Luck with that.


This thread reminds me of the people on here who ask about driveshaft vibration, ignore the advice they get, then start a thread a few weeks later about a cracked tranny housing and fluid sprayed all over the underside of the car. :lol:

I had the same thought myself. He didn't want an honest opinion .... just confirmation that what he was doing was OK. :rolleyes:

[SC Cheesehead]

Well documented cases of people ignoring the "Required" label on the inside of the fuel door and has had catastrophic results...

^^^^ +1 ^^^^

Just ask fastblackmerc about his experience at MVIV.

I was running right behind him when it went BOOM!

Unless your car's tuned for 87 octane, you're kinda playing Russian Roulette, IMO.

[Bluerauder]

Unless your car's tuned for 87 octane, you're kinda playing Russian Roulette, IMO.

..... with 5 loaded chambers. Very poor odds. :D

[martyo]

And I almost missed this thread!!!

[guspech750]

Lets lighten up, i'll start.

Melanie wants me to teach her how to brake torque next spring :) This brought a tear to my eyes.
Sadly Bob. I will never feel your joy.:alone:

Oh well. JUST MEANS MORE FUN FOR ME!!!!!:burnout::D

[LANDY]

Put 93 octane and that's it.
Picking Gasonline is like picking your women
You always want have the best.

[guspech750]

Put 93 octane and that's it.
Picking Gasonline is like picking your women
You always want have the best.

Hey!! Some here like men too such as CBT. He has feelings you know. :)

[4drcbra]

the amount saved is minimal between octanes. Just stick with the recommended stuff and cut somewhere else

[Motorhead350]

Tbone, just stick to 93. Don't let $3 savings turn into a $3,000 fix down the line.

[Dragcity]

To answer your original question....


The carbon buildup is due to the computer adding more fuel to richen the mix to AVOID pinging. That extra fuel does not all burn all the time , as more fuel is added and timing is retarded, to avoid the pinging your knock sensors are detecting, makes more unburned fuel.

As such, unburned fuel in the combustion chamber, over time, equates to carbon build-up. Which in turn holds heat, compounding your problem..... More heat = pre-ignition (pinging) = retard timing + add fuel.... A viscious cycle.

Properly running engines are more effecient, in many ways. I believe you will indeed increase your fuel economy over time if you run the correct fuel for your tune.

I think you are putting more miles on your engine than you realize by running under 93 octane on a 93 octane tune.

Just my thought on the matter, which I hope helps you....

[rayjay]

I agree with what DragCity said. It makes sense. Gas in NYS is not cheap right now. $3.40 something for 93 which we have to use in our Lincoln LS because no one carries 91 octane here. The way my wife drives I told her to stay with the 93 vs 89. (speed racer) I can not afford to replace that little 3.9 Lt Jag engine. In the Marauder a load of bad 87 plus a WOT run could very well send enough detonation down the crank to toast the oil pump. Before you realize whats going down you're out a engine. Just my $.02

[SC Cheesehead]

I agree with what DragCity said. It makes sense. Gas in NYS is not cheap right now. $3.40 something for 93 which we have to use in our Lincoln LS because no one carries 91 octane here. The way my wife drives I told her to stay with the 93 vs 89. (speed racer) I can not afford to replace that little 3.9 Lt Jag engine. In the Marauder a load of bad 87 plus a WOT run could very well send enough detonation down the crank to toast the oil pump. Before you realize whats going down you're out a engine. Just my $.02

That's what happened to FBM, and he wasn't even running WOT.

[dakslim]

I have 110,000 miles on my Marauder and I've always used 93 octane as well as change the oil (Mobile 1) every three thousand miles. Some have said that you don't need to change the oil that often but I don't care! It makes me feel better, end of story.

[SC Cheesehead]

I have 110,000 miles on my Marauder and I've always used 93 octane as well as change the oil (Mobile 1) every three thousand miles. Some have said that you don't need to change the oil that often but I don't care! It makes me feel better, end of story.

If I had your money, I'd change it more often than that... ;)