85 instead of 87 OK? Expedition, Denver, 5280 ft.

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Robert_Gift

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Denver, Colorado, USA
['99 Expedition, 4.8 V-8, 4WD, Emergency Vehicle.]
Just rushed 108 miles red light and siren Denver UP to Vail.
In Vail I refueled nearly empty tank with 10 gallons of 85 octane @ $2.75/gal. (Much le$$ than 87 octane.)
Owner's Manual requires 87 Octane.
No pinging when back in flat Denver.
But, will 85 be "less efficient" and I will need a little more gas and therefore little money is actually saved?
Thank you,
Robert
 
The 85 Octane will serve you well!

The higher the altitude, the lower octane you want in your vehicle!

Run a few tanks and keep track of your mileage.
 
just go whith the manual...ford expy has many dentonation problems the software update fixed and advised to use 87 octane in high altitude..however;srdriver is right but i would stick with what is recommended.....i use 87 in my 98 expy
 
Quote:

The 85 Octane will serve you well!

The higher the altitude, the lower octane you want in your vehicle!

Run a few tanks and keep track of your mileage.

Click to expand...

Good idea.
But everytime I try to get mileage, it gets ruined by emergency runs. I am not able to drive efficiently as I usually do: gentle accelerations, coasting whenever possible, anticipating signals and trying to arrive after they turn green, etc.

On the 108 mile run to Vail I blew half a tank - going mostly up hill, against a westerly headwind, excessive speed, plus load on alternator from emergency lights.
Normally I baby the vehicle and drive 50 in 55 mph zones.
 
Quote:

just go whith the manual...ford expy has many dentonation problems the software update fixed and advised to use 87 octane in high altitude..however;srdriver is right but i would stick with what is recommended.....i use 87 in my 98 expy

Click to expand...

Oh. Well that ruins my plans!!
How does one get the software update?
Thank you,
Robert
 
CSU Alum here. No problem running 85 octane in two Ford F150 4.6l V8 engines ('97 F150 and '99 F150) all over the front range and into the mountains. My force of habit was to fill up with 87 octane on the way out of town so on my return to the lower elevations of eastern Nebraska I still had mostly 87 octane in the tank. (Gotta love doing 900+ mile drives home on one stop for gas
smile.gif
)
 
I have a classmate who lives in Denver who runs 85 Octane in both his Ford Vehicles there with no problems.

Works well and costs him and his wife less for fuel too.
 
really, the lower the octane you ca get way with at a given spark advance, the better.

You always want to run as low an octane as possible without inducing detonation, knocking, etc... Sometimes the point is moot if your engine will advance timing for more power (advanced timing generally means better efficiency too), but even then you want the lowest octane that will buy you maximum advance or optimized fuel economy.

Good luck!

JMH
 
I've used the 85 when I am in Utah and it serves me well. That is at 4400 feet. I do track my MPG and it went down a little, but I am certain that was because we did more city driving during that time. No detonation problems on a 2002 Tundra or 2006 Honda Odyssey. Didn't try it in my Harleys though - one of them pings more than a table tennis match in China unless there is 91 in it. Wasn't going to chance it...
 
I live here is Highlands Ranch CO. I just ran a tank of 87 Diamond Shamrock gas and got 16 MPG. The last 3 tanks I used 85, 1 fill up a DS, and 2 at Shell, got 15 MPG on those 3 tanks. Maybe the winter blend is being discontinued or 87 is making better fuel mileage, I need to run a couple more tanks.
 
hi wags i live couple miles from you west in the foothills...i use shell because its a top tier gas..would not use shamrock because they use ethenol all year long...shell has no ehtenol in it now season is over...the reason i know is i ask the tanker delivery driver's guy does not add ethenol(season is over)..conoco is a top tier gas but they also use ethenol it their gas all year long (their drivers add it in)...i just use shell..i use 87 as per ford and 91 on occasion..
 
Yeah i have to agree with wags. I own a 97 geo prizm with the 4a-fe 1.6 and it too most of the time likes the 87. I seem to get further on a tank of Safeway (I know) or diamond gas. The conoco's in longmont seem to give me less mpg. My dad also noticed the samething on his 96 ford Aerostar, go figure
 
IIRC the octane plug was last used by Ford on OBD I systems. OBD II started in 96. I certain that there is no octane plug for a 99 Expedition.

The real issue here is that an engine requires less octane at higher elevation. The only thing to be careful of is to not fill up with low octane at high elevation and then start a trip into lower altitude. For example, don't fill up with 85 octane in Cedar City, Utah, and then head for Las Vegas. You could be in trouble on any uphill grades.
 
Big Jim.

You sir are incorrect.

Would you like a photo of the octane plug on my 98 f150?

Its also on my 96 thunderbird which is obd2.

If it has a 4.6, i know what i'm talking about.
 
At higher altitudes the 85 octane will work just fine. Do a search in Yahoo, Google, etc., when you have some free time and you will find reasons why 85 octane should be used at those altitudes.

Sound like you would like a fuel cost savings? Go with the 85 Octane.
 
In my one gas vehicle, 85 octane works just fine. If I recall correctly, you can decrease octane by 1 point for every 1000 foot gain in altitude. If you are running a turbocharged/supercharged vehicle then you need to use the octane reccomended by the manufacturer.

I'm currently burning 47 in two of my vehicles....cetane that is ;-)
 
If the owner's manual calls for 87 octane at sea level then 85 octane ~should~ be correct at altitude.

I still believe in experimenting to determine which fuel runs best for your vehicle. The owner's manual is the best place to start, and then the vehicle specific forums sometimes have some useful info.

Higher octane is not always better in modern engines, but some cars seem to run better with higher [or lower] octane than specified.

I'm happy whenever I can run 85 octane. Buying premium or diesel in Vail is a ripoff... we suffer some of the highest price fixing in Colorado.
 
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