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Discussion Starter · #1 · (Edited)
I'm sure this post will get some attention and a lot of comments but i'm not sure anyone will 'truly' know the answers. A family friend i've known for years recently retired as an engineer at Exxon Mobile in Germany. He is and always has been EXTREMELY adament that higher octane gas is a ploy and it is not needed. I've read very similiar articles including one good one about a year ago that was titled something like "Gas, the biggest scam of our time." --or something to that affect.

I also know from experience once a car is "trained" to run on higher octane, it craves that octane or the performance may be weaker or you may get a pinging type noise from the engine. Armed with that information I have only filled up once since getting my Charger R/T 5.7L Hemi and filled up with 87. The car is running excellent with 87, however, I am stuck between believing gas is just a scam (even though much experience and many articles state it is) and other articles i've read where people claim to get better gas mileage and performance with higher octane.

Now with this being said, if my car runs this smooth on 87 now, why not continue to use 87? I think it's also kind of interesting that different parts of the country have different grades of gas and if it were "SO" important to have that higher octane how come it isn't available in many states? :knockout: For example, i'm from Florida originally and they don't even HAVE 87. The grades are 89, 91, 93. Out in Florida if you are using "89" that's considered the Lowest grade.

However, i'm in California now and the grades are 87, 89, 91 So a grade LOWER then 89, and LOWER then 93. Again, if grades were 'SO' crucial, then you'd think they'd be mandatory everywhere. That simply isn't the case.

All this stuff points to what the Exxon Mobile Engineer has told me for quite a while as well as my very own performance i'm seeing with 87. Honestly, if i'm seeing this kind of performance, why wouldn't I use 87? Can I really expect to get some kind of damage by using 87 a zillion years from now?

If so, no biggie, I have the lifetime powertrain warranty with zero deductible..lol...but seriously, does anyone else see the gas grades as huge scam and use 87 octane in their 5.7 or even 6.1L Hemi's?
 

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I've ran '87 since the DAY I bought my baby. I'm up to 12,000-ish miles (since Memorial Day '07), and when I push the gas, she GOES.
 

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Correct me, if I am wrong, I believe California uses reformulated fuels, which may affect engine operation. If so, depending on the altitude you are operating at, you may or may not be able to "easily" get away with 87. I am at 2800 feet and I run it all winter long, and then run 89 or 91 in the summer heat, depending if I plan to go to the races or not. I have a Dashhawk hooked up and monitor knock retard by the PCM. With 87 on the highway (in rolling hills) I'll sometimes pick up as much as 5 degrees (usually 1.5-2 degrees) of spark retard due to the knock sensor picking up pinging. Around town I never have a problem with spark retard. So, I would recommend you try it, depending on your location and driving habits. If you get spark knock, the PCM will just retard the timing until it stops. At worst, you'll lose a little mileage, at best you'll save a buck or two. By the way, I also usually get a little better mileage in the winter with 87, but I suspect the lower ambient temps. have something to do with it.
 

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I tried 87 and 89. I measured gas mileage and never could detect any difference. Some people will claim that timing is retarded with 87, but I can't notice it. If I was going to the track I'd probably use 89, but in every day life I'm gonna stick with 87. I'll take the free breakfast sandwich with every fill up I get by the savings.
 

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You also have to realize that those are minimum standards that are listed. So you might have 88 Octane coming out of the pump from a 87 listed pump sometimes there is 89 Octane so it is a scam as far as that goes. Unless you are a extreme speed freak 87 octane will work. Actually it even states in your Users Manual..( I know what a geek he read that thing) say that anything higher than 87 or 89 doesnt sit well with the MDS system. Bu to each his own. It would be a difference of a couple dollars a fill up anyway so.. It comes down to personal preference
 

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Discussion Starter · #6 ·
wow, I really expected to get some grief from the type of people who think they are "know it alls" but really know nothing. As I said, I didn't want to start a war but the guy that worked for Exxon Mobile and recently retired is one sharp cookie. He really knows his stuff and i'm not just referring to gas or oil. When he speaks I listen so he's been telling me this for a while and when he visits in the Winter from Germany with his wife I go to dinner with them or even costco to grab a few things. He always uses the lowest octane in his car so he practices what he preaches.

His English is not perfect so when he explains the details of why the higher grades are for the most part a scam I don't understand every word. I just thought it was very interesting and the article I read about a year ago almost mirrored his statements. I wish I could find it but like I said the title said it all..something like Gas Grades, the biggest scam of "OUR TIME." lol...

Anyway, glad to see other people are using 87, b/c quite honestly with the performance I am getting I wasn't going to change anyway...lol...I still would respect any other "factual" statements though which is why I asked.


I guess with this being said, anyone gonna come forward and claim why their 89, 91, 93, 95, 100 octane or whatever it may be is much better then 87?
 

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I used 93 only in first R/T ( had 5,000 miles when I totaled it), and 89 only so far in the Daytona (4,000 miles). The first R/T felt like it drove alot better, and got better gas mileage for sure
 

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You also have to realize that those are minimum standards that are listed. So you might have 88 Octane coming out of the pump from a 87 listed pump sometimes there is 89 Octane so it is a scam as far as that goes. Unless you are a extreme speed freak 87 octane will work. Actually it even states in your Users Manual..( I know what a geek he read that thing) say that anything higher than 87 or 89 doesnt sit well with the MDS system. Bu to each his own. It would be a difference of a couple dollars a fill up anyway so.. It comes down to personal preference

It doesn't say that in my owners manual, it says 89 or higher.
 

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wow, I really expected to get some grief from the type of people who think they are "know it alls" but really know nothing. As I said, I didn't want to start a war but the guy that worked for Exxon Mobile and recently retired is one sharp cookie. He really knows his stuff and i'm not just referring to gas or oil. When he speaks I listen so he's been telling me this for a while and when he visits in the Winter from Germany with his wife I go to dinner with them or even costco to grab a few things. He always uses the lowest octane in his car so he practices what he preaches.

His English is not perfect so when he explains the details of why the higher grades are for the most part a scam I don't understand every word. I just thought it was very interesting and the article I read about a year ago almost mirrored his statements. I wish I could find it but like I said the title said it all..something like Gas Grades, the biggest scam of "OUR TIME." lol...

Anyway, glad to see other people are using 87, b/c quite honestly with the performance I am getting I wasn't going to change anyway...lol...I still would respect any other "factual" statements though which is why I asked.


I guess with this being said, anyone gonna come forward and claim why their 89, 91, 93, 95, 100 octane or whatever it may be is much better then 87?

LOL, dude its 1am and a Friday nite, well now Sat morning no ones on. Give em time, they'll come out
 

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87 should work fine, if your not performance oriented. But you can put 89 or 91 octane in , hook up a star scan and actually watch you fuel and igntion tables adjust for more output When the ecm sees the ability to advance timing without detonition it does it to whatever point its parameters are in . If your not re programming (aka reflash or programmer) or going with cams and stuff run your 87. I actually did a testand posted it on here and got my best gas mileage with 91 over , 87,89 and 89 with 10% ethanol blend. Even mathmatically made more sence to spend the extra 20c a gallon to get that extra gas mileage. Not by much though . Just pennies.
Also i think the myth from old times is primarily due to the people that think that octane is a hp increase. They are the ones i normally hear saying its junk because they dont understand what the octane actually does. Most of us now adays understand octane is nothing but the resistance to detination but you cant explain that to a lot of older people that are set in their ways.
 

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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.

The compression ratio of your engine determines the octane rating of the gas you must use in the car.

Our hemi has a compression ratio of 9.6:1

Use 89.....
 

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89 is recommended according to the manual. 87 will work though. I recently started putting 93 in the car and noticed a difference though. I did the WIKIGOOGLE combo for research and its a mixed bag. Trial and error, higher octane wins. I don't think I'll do the 100 octane though as that just seems pointless without tuning the car.
 

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Well when I get outta work I am gonna go check the manual for my 2007 .... goodnees I will feel like a dweeb if I got that part wrong... Crow where did you get that Compression ratio/Octane info? Now I will have to see if it makes a difference in my mileage...
 

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My understanding, is that you want to go with the lowest octane, that will give you the most power. The more efficiently your engine is burning the fuel, the more power you will get. If you run a lower octane on a higher compression engine, then the fuel will combust prematurely from the pressure. If you run a higher octane, then what your engine is made for, then the fuel may not burn completely, leaving residue (bad). Before I got the predator, my RT ran best on 91. It was defiantly sluggish on 89 (probably from the computer slowing the timing to reduce knocking.) at 93 octane I didn't run as well either. On my bike, stock it ran best on 87 octane, after I got a new ignition module to advance the spark, and run higher compression, I need to run 91.

I think that where the novice makes the mistake, is in seeing someone with a supped up car, putting higher octane in, or running higher octane for racing, and they think that they can do the same with there car. Higher octane doesn't produce the power, but it is required for the cars that are designed for higher HP.

I have heard a rumor that with the minimum octane rating some gas stations will put 89 octane in both there 87 and 89 pumps, and 93 in there 91 pumps, or even have the coming out of the same tank. But while I'm sure that your friend knows a lot about gas and oil, if he said something similar to the above, I would believe him. But as stated, I think that your friend may not know a lot about engines (no offense).

-brian
 

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OK I figured out wher ei went wrong.... It was the oil that was critical to MDS function... geesh I am glad that I haven't been trying to put gas in my dipstick under the hood.... LOL. Yes 89 is recomended.
 

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crow is right... gas isnt a scam at (or at least the octane ratings aren't).. its all about compression and if you fill cars with higher compression with 87 you can hear the fuel detonating, which is very bad. they have different grades at different gas stations and states and stuff, but it is perfectly safe to mix them to get your desired grade.
 

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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.

The compression ratio of your engine determines the octane rating of the gas you must use in the car.

Our hemi has a compression ratio of 9.6:1

Use 89.....
This is pretty much spot on. "Octane" itself is a hydrocarbon, and the octane ratings of the different formulations of gasoline compare how compressible a fuel-air mixture before detonating to that of Octane. A 100 octane fuel would be 100% as compressible before detonation as pure octane fuel.(simplified explanation) Ideally for maximum power, economy, and clean emissions, you would want to compress your fuel-air mixture as much as possible in the correct ratios and ignite it by spark just before detonating.

Running too low an octane rating fuel for an engine causes detonation instead of combustion that is percieved as pinging or knocking. Most modern vehicles can accomodate for this within a range by pulling timing and air/fuel mixture adjustment. Optimal output isn't achieved, but as long as the engine has enough adjustment, it can be used without damage.

Running too high an octane rating fuel for an engine leads to incomplete combustion and higher CO and NOx content of the exhaust. The lifespan of catalytic converters are reduced, and optimal output is not achieved since the ideal combustion reaction is not occuring.

"Grades" of fuel is a deceptive term, since low, mid, or high are no "better" than the other, just differently formulated for optimal performance in different engines. The detergent packages that are included with the fuel are the same accross all octane ratings, and really very similar between all the brands. Beyond all of this, the idea that one brand fuel is better or worse than another is mostly marketing and no real science at all, especially since most of it is transported by pipeline.
 

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Right, and heres the disconnect.

Your German friend corrected one myth with another:)

The one he corrected is that more octane gives better performance in normal cars

That is indeed a myth. As said elswhere here, maybe %90 or better, back in the 80s, early 90s, say %99, of all vehicles will see no gains in any way from increased octane over recommended.

But, sadly, his reasoning was another myth, that there are no differences in gas grades. Thats like saying that becuase %90 of people cant tell a cubic zirconia (fake diamond)from a real diamond, there is no difference.

There is indeed a difference. Just that most vehicles wont change what that do based on it, therefore its a waste.

Wifes truck lives happily on 87. SRT gets nothing less than 93. Old SRT-4 got occasional doses of +100 rcegas, but it had a special setup I could use to retune the engine to advance timing to take advantage of that octane.
 

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I used 87 until i found 89, then ran that grade until I installed the Superchips 91 tune, and have been running 91 since. When i know that i'm going to the track I'll use 94 the week prior and mash the hell out of the gas up until race day.
 

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You know....I do notice a great change in my MPG and response since using 93. I have always used the highest octane in my previous cars that asked for it.

You can really get some stinky 87/89 in the world today. Not saying I always had great 93, but in 95% of the time, it's a higher grade fuel, which will probably give you less 'gunk' in the engine....

So, to sum it up for me.....it's just a cleaner, more refined, selection,,,and anyway, why would a car manufacturer tell you to use 92 or 93 only (Like my 2005 T-Bird stated 92+ only)...? There's something in it that's better!

- Mark
 
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