Hi! Wondering if anyone has used Octane 93 gas on their expys? I"m currently using Octane 89 after upgrading from 87 coz if I put 87 in the car, it feels sluggish. 89 does help a little, but not that much.

 

I only use 87 octane in my expy, 1998 4.6. I have an ongoing idle problem and one of the first things I was asked is what octane I'm using. The owners manual suggests only using 87 octane and with the price of gas and the terrible gas mileage with the expys, I'm fine with using the 87. Now I have no mods in my expy, so I'm not sure if having mods means needing the higher octane....

John B.
1998 Expedition 4.6

 

I use 89 and maybe once a month I'll fill up with 93/94. I still can't bring myself to using 87. A few months ago Car and Driver did an article on manuf. recommendations on Octane and then did a little comparison test on a few different vehicles. In a nutshell, in today's "smart" engines octane means nothing from a damaging your car perspective, the ECU/knock sensors will retard timing to prevent engine knock from lower grade fuel, in performance cars though this retarded timing will have a slight but probably noticeable effect on performance...until you fuel up with the good stuff again anyway.

 

I see your point in using such a low grade gas (87). You sometimes wander what part Water is to what part Gas. Ive had no problems running 87 though. I put 94 in once a month, with the occasional Dry Gas to keep it running clean.

 

:-X23 Many consumers fall into this mistaken idea, i guess they think that the higher price equals higher quality but. . . The octane rating system is NOT and has never been a measure of gasoline quality. The octane rating is simply a so called "anti-knock" index (detonation of the fuel/air mixture prior to ignition by spark) The higher octane ratings are typically required by high compression, supercharged, spark advanced, otherwise modified or performance motors. The higher octane means the fuel will actually be harder to burn and can therefor "hurt" you by increasing deposits and cuasing your CAT to burn the fuel your motor doesn't. The measure of quality is the additive package, think Texaco system 3, Chevron Techron, etc. Higher octane run in an engine not designed for it can actually increase

I have been in the petroleum industry for over 18 yrs and performed testing at most major and unbranded outlets for 10 of those years.

Allow me to copy the anti-cigerette ad men in saying that the "truth" is that putting premium unleaded fuel into the tank of a vehical designed to run on 87 octane is a waste of good money. Further, many well intentioned owners who think that they are giving the best to their baby by going to unbranded/cheap gas outlets are doing more harm then good. Though many of these get their gas at the same terminals as the majors, sometimes the additive packages don't make the trip. Once more some have been known to use their own "additive packages".

For instance I caught a oil jobber, now out of business, in North Carolina that was selling a blend of 60% gasoline and 40 % ethenol. With ethenol being about half the cost of gasoline, he would then "pocket" as much as $0.20 per gallon extra "profit". I also caught my share of dealers that must have "mistakenly" had reg unl delivered to the wrong underground tank (always seemed to be the prem unl tank.

Another Item all together is the meter accuracy in the dispensers themselves. These are "checked" by the various state dept. of agriculture officials annually and will be put out of service if they are not within 5 cubic inches per 5 gallons dispensed. They are however far from tamper proof.

Now don't get me wrong, I am not trying to sound alarms of wide spread fraud throughout the industry. There are laws with real teeth in place (hugh fines) as well as independant inspectors, random sampling, etc. to protect the consumer. This I know first hand. I just want you all to know that like every other consumer product, there is always the chance of fraud. When you factor in the incredably tight margins, the fact that the consumer doesn't even SEE the product and the general misunderstanding of the octane rating system, you can see the need for compliance testing.

In summary, If you are still with me after such a long read (sorry) if your engine is designed/set-up to run 87 octane run it and save your extra $4-$5 per tank for real goodies.

Petrol

 

Petrol, what a great write-up. Thanks a lot for clearifying this issue. With your permission I am going to send a copy to my oldest daughter (the one who drives cars with bowties) as she feels she is being good to her car by using premium. She then goes on to complain about not having money to by shoes or go the movies....

The more I think about this, there are about 10-15 people I know who should read this. I think I will just point them all to this site and this board. Keep the good words flowing.

 

So, if the Expy manual says to use 87 octane, will using higher octane cause problems?

John Breeding
1998 Expedition 4.6

 

jbc67, I guess you did not understand much of what petrol wrote?

Short term (a tankful because the regular pump is broken) no problem, just costs more. Long term, early catalytic converter and plug failure, shortened life on valves and pistons. If you do something to your truck to change the way it runs, like reprograming the ECS with a high performance chip, modifying the engine such that it has a higher compression ratio, etc., then higher octane may be indicated. Stock on our trucks equals 87.

Its your truck and your money, you make the choice. I think if the OEM recommends something one should probably do that for the best results.

 

I mean for you to get the idea that running prem unl will do serious damage to your motor, but can lead to minor problems over long term. Most of the damage will be done to your wallet as prem unl typically runs 15-25 cents more per gallon, money that might be better off thrown in box in the closet, pull it out after a year and use it to treat you wife to a special night out or something.

While there are cases where motors that will run better on high octane fuel then the manufactures recommendation of 87 oct reg unl, they are very few and far bettween. Most often this is the case with a high mileage vehical, like the company truck I currently drive that has at this writing over 178,000 hard miles (engine has not been rebuilt & has only routine maintenace with no problems). I recently started to use mid grade (89 octane) fuel in this truck as it was begining to "ping" or "knock" on 87 reg unl. I think the reason for the "ping" is carbon deposits have finally began to sneak into the cylinders. These deposits will "hold" heat and give pre-ignition or "ping" problems. The higher octane, ie harder to burn fuel helps to prevent this early detonation.

Once agian, the main point I want to make is that octane is not a refferance of gasoline qaulity, the detergent aditive package is.

Petrol

 

I agree that 93 octane is usually just a waste of cash, but I have always run 87 in my 97 Expy 5.4, until I used the Hypertech power programmer. now if I dont fill up with 93 the truck pings terribly, not just uphill either. I have tried some of the "octane boosters" and none work as well as just forking out the extra $5 at the pump.
If I set the programming back to stock, the pinging will cease.
I called Hypertech on this, and because of the ignition advance that the programmer provides, they agree that I should run only the highest octane avail. in my area (93)

 

 

I think that most performance chips require the use of premium unl fuel, unless it's a 'flip-chip' that has daul octane settings.

 

Petrol,

Thanks for the info on octane but it did raise one question with me. I have been reading about the performance chips and most seem to require premium octane fuel. Under these circumstances would using premium eventually harm the engine or catylitic converter?

 

Wow, Petrol... Great info. Thanks for going into such detail. I just now read your March post.

Can I ask: You mention Texaco and Chevron's blends, is there a top 2 or 3 choices you can say are your preferences based on your personal experience? Or would that decision be different depending on region?

Thanks again for the great info. Printed one for my archives.

 

[updated:LAST EDITED ON 24-Jun-02 AT 08:00 PM (EST)]> I have been reading about the performance chips
>and most seem to require premium octane fuel. Under these
>circumstances would using premium eventually harm the engine
>or catylitic converter?


No, with most every chip I have seen the requirement is that you use premium unleaded. You would then risk damage by NOT running with premium.

You can also question Ken here at this site as he is a vast source of knowledge, including the subject of performance chips.

My limited knowledge is that most chips modify, among other things, the advance curve of the ingnition timing and therefor are able to unlock some of the performance potenial of these modern motors at what is a real good bang-4-the buck ratio. The trade off is a requirement to run 91 or better octane fuel.

If you have a 'chip' and don't run premium unleaded you will experiance detonation, wether you hear it our not, and it can/will cause damage over the long haul. I wouldn't panic if I was close to empty and 'HAD' to put a couple gallons of lesser grade fuel (meaning octane or brand)in the tank to get by until I could top her off with the good stuff, but I wouldn't make a habit of it either.

Petrol