What octane do you use

[BmacIL]

Well I cant tell you I dont know much about all the details, but a few things I wanted to mention:

To the person who said manuals have to say 87 octane for marketability is wrong. I own 3 vettes, my 2001 AND my 2012 clearly state in the manual 93 octane, it states that 87 can be used but will take a performance hit, and the possibility of knocking, and is not recommended. Vettes are also high performance cars, yet it does not state you can use 87 octane.

Also ethanol additive doesnt increase fuel efficiency, but reduces it (Its "enviromental friendly" to reduce emissions), also unless things have changed in the last 10 years (Which I seriously doubt) 87 is as they say dirtier then 89 (which is only slightly better) or 93 (which has the least impurities). There is more impurities in 87 which cause deposits in the engine itself which after time causes build-up which also reduces horsepower, efficiency, and reduces the life of the engine.

My mechanic told me years ago to stay away from 87, he also said if you have a normal beater use 89 if you dont want to use 93. if you have ever looked at 87 octane gas it has a slight yellow tinge to it opposed to 93. And considering how cheap gas is right now, why is anyone willing to take the chance and nickel and dime on fuel when you just spend 1/4th-1/2 of your yearly salary buying a mustang?

Remember also we have emissions here in the US, and we have requirements to have recirculating unburned fuel those canisters, fuel filters, etc also are effected by the lower octane and deposit build-up.

Its real simple: 87 octane burns like oil, 93 octane burns like natural gas, which would you rather?

I can't even....... What? The only correct things you said are that higher ethanol content reduces fuel efficiency and that gas is relatively cheap right now. Literally everything else you said about gasoline is wrong, particularly your last statement. The lower the octane rating, the higher the volatility and the easier it burns (takes lower temperature and pressure to ignite).

:tsk:

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[GuardGT]

my car (tune and exhaust auto) was pulling timing in the back half on CA 91. pulled a few degrees and picked up 2 mph. these cars like octane when pushed, no mystery. id run 93 if we had it.

 

[15 Stang]

Well
My mechanic told me years ago to stay away from 87, he also said if you have a normal beater use 89 if you dont want to use 93.

Your mechanic is blowing smoke up your keester.
The only time that you will need fuel with a higher octane rating is:

• you have an after market tune installed
• you are towing a trailer (re: higher manifold pressures)

Ask yourself this question, how far are you pushing the engine past 4,000 rpm's in your driving? That's where you will need the higher octane fuel.

Driving around town in traffic doesn't require the additional resistance to knocking, or the reason to run a higher octane fuel. Driving on the interstate at 75-80 mph doesn't require fuel with an octane rating higher than 87.

The straw color of the fuel doesn't have any bearing on the quality of the fuel. What does have a bearing is the ethanol content. Avoid fuel it the ethanol content is higher than 10%. Have you tested your ethanol content of the fuel in your tank?

Dave Z.

 

[jasonstang]

I agree with FordTechOne that the engine doesn't adjust to lower octane fuel after burning it, but I don't agree with any of his other statements. Ford recommends 87 octane fuel in the 5.0, so of course the engine was designed for 87 octane fuel!

It's designed to run safely on 87 but designed to run optimally on premium.
Can I drive the Mustang on safely on Prius tires? Absolutely. Are these tires optimum for putting down 435hp? Not really.
If you drive your car never getting on her hard hitting 6000rpm and pedal to the floor, you can probably get away with 87.
The way I drive, I don't want to worry about computer pulling timing and stuff because of knocks when I WOT hitting redline.

 

[BmacIL]

Your mechanic is blowing smoke up your keester.
The only time that you will need fuel with a higher octane rating is:

• you have an after market tune installed
• you are towing a trailer (re: higher manifold pressures)

Ask yourself this question, how far are you pushing the engine past 4,000 rpm's in your driving? That's where you will need the higher octane fuel.

Driving around town in traffic doesn't require the additional resistance to knocking, or the reason to run a higher octane fuel. Driving on the interstate at 75-80 mph doesn't require fuel with an octane rating higher than 87.

The straw color of the fuel doesn't have any bearing on the quality of the fuel. What does have a bearing is the ethanol content. Avoid fuel it the ethanol content is higher than 10%. Have you tested your ethanol content of the fuel in your tank?

Dave Z.

That's not entirely true. While knocking most definitely can occur at high RPM, you're much more likely to experience it at high load/throttle and low engine speed. This is a condition where cylinder pressure is high but piston speed is lower, increasing the allowable time for pre-ignition.

 

[tcman54]

Everybody keeps saying the Mustang was designed to run on 87 octane, I just don't think that's true.

Why then would ford list the maximum amount of hp one could get by saying it was done with 93 octane.

The car was designed to run on 93 octane but will run on 87 octane with a slight decrease in performance.

To most people there is very little difference for those last 5 or 10hp so it comes down to money, around here 93 octane is about 50 cents a gallon more expensive than 87 octane.

I am trying to get every last drop of performance out of my ecoboost that I can, so I switched from 87 (the first 10 tanks) to 93, I drive like a maniac and do get the sense of a little more oomph, is that worth an extra $7 or $8 at the pump every fill up, pretty not, but to each his own.

It will be interesting to see how many people switch from 93 down to 87 if the price of gas goes up to $4 a gallon.

Terry

 

[mustang1]

Anyone with an Ngauge who can data log the stock tune on 87 octane? Theoretically we would see evidence of knock that would pull timing.

 

[mmdpg]

"Back in the Day" cars would knock most under hard acceleration at the lower end of the RPM range and when you lugged the engine, too high a gear for the load on the engine.

 

[jasonstang]

"Back in the Day" cars would knock most under hard acceleration at the lower end of the RPM range and when you lugged the engine, too high a gear for the load on the engine.

Well back in the day with fixed ignition and valve timing, there will be too much advance at lower rpm because how the timing is tuned for higher rpm.

 

[daytripper]

Well back in the day with fixed ignition and valve timing, there will be too much advance at lower rpm because how the timing is tuned for higher rpm.

The valve timing was fixed but not the ignition timing. Either vacuum or centrifugal or a combination of the two was used for longer than most people have been alive.

 

[1BadAss16CS]

Two different articles quoting FORD on the 302 engine. The Ecoboost may be different.

Car Pro USA -

"The 5.0-liter V8 (I still prefer 302) calls for 91-octane gas to maximize power, but Ford admits that with 87-octane, you only lose 1% of the horsepower."

Car and Driver -

" If you fill up using 87 octane, you’ll be down on horsepower—by about one percent according to Ford. So it’s highly unlikely you’ll notice."

 

[jasonstang]

The valve timing was fixed but not the ignition timing. Either vacuum or centrifugal or a combination of the two was used for longer than most people have been alive.

Depends on what engine I guess. I had a 97 Wrangler 4 cylinder. That thing was fixed everything.

 

[awmustang]

Everybody keeps saying the Mustang was designed to run on 87 octane, I just don't think that's true.

Why then would ford list the maximum amount of hp one could get by saying it was done with 93 octane.

The car was designed to run on 93 octane but will run on 87 octane with a slight decrease in performance.

To most people there is very little difference for those last 5 or 10hp so it comes down to money, around here 93 octane is about 50 cents a gallon more expensive than 87 octane.

I am trying to get every last drop of performance out of my ecoboost that I can, so I switched from 87 (the first 10 tanks) to 93, I drive like a maniac and do get the sense of a little more oomph, is that worth an extra $7 or $8 at the pump every fill up, pretty not, but to each his own.

It will be interesting to see how many people switch from 93 down to 87 if the price of gas goes up to $4 a gallon.

Terry

Check your owner's manual and you'll see why I think the car was designed to run on 87, but to take advantage for higher octanes. You'll note the V6 does not appear to be designed to take advantage of higher octanes.

2.3L EcoBoost and 5.0L V8 Engines
We recommend regular unleaded gasoline
with a pump (R+M)/2 octane rating of 87.
Some stations offer fuels posted as regular
with an octane rating below 87, particularly
in high altitude areas. We do not
recommend fuels with an octane rating
below 87.
To provide improved performance, we
recommend premium fuel for severe duty
usage, such as trailer tow.
3.7L V6 Engines
We recommend regular unleaded gasoline
with a pump (R+M)/2 octane rating of 87.
Some stations offer fuels posted as regular
with an octane rating below 87, particularly
in high altitude areas. We do not
recommend fuels with an octane rating
below 87.

 

[15 Stang]

That's not entirely true. While knocking most definitely can occur at high RPM, you're much more likely to experience it at high load/throttle and low engine speed. This is a condition where cylinder pressure is high but piston speed is lower, increasing the allowable time for pre-ignition.

How are you going to get high loads and low engine speeds without abusing the engine?

Its exactly true because the only way that you can achieve your conditions is by:

1. towing a trailer
2. running an aftermarket tune

The engine module electronically controls and adjusts the parameters to prevent engine damage.

 

[AZ_Ryan]

Well I cant tell you I dont know much about all the details, but a few things I wanted to mention:

To the person who said manuals have to say 87 octane for marketability is wrong. I own 3 vettes, my 2001 AND my 2012 clearly state in the manual 93 octane, it states that 87 can be used but will take a performance hit, and the possibility of knocking, and is not recommended. Vettes are also high performance cars, yet it does not state you can use 87 octane.

Also ethanol additive doesnt increase fuel efficiency, but reduces it (Its "enviromental friendly" to reduce emissions), also unless things have changed in the last 10 years (Which I seriously doubt) 87 is as they say dirtier then 89 (which is only slightly better) or 93 (which has the least impurities). There is more impurities in 87 which cause deposits in the engine itself which after time causes build-up which also reduces horsepower, efficiency, and reduces the life of the engine.

My mechanic told me years ago to stay away from 87, he also said if you have a normal beater use 89 if you dont want to use 93. if you have ever looked at 87 octane gas it has a slight yellow tinge to it opposed to 93. And considering how cheap gas is right now, why is anyone willing to take the chance and nickel and dime on fuel when you just spend 1/4th-1/2 of your yearly salary buying a mustang?

Remember also we have emissions here in the US, and we have requirements to have recirculating unburned fuel those canisters, fuel filters, etc also are effected by the lower octane and deposit build-up.

Its real simple: 87 octane burns like oil, 93 octane burns like natural gas, which would you rather?

Oh my dear sweet lord. This is why Internet car forums get a bad name. :frusty:

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