Ford E350 V10 Octane Question

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DanKearney

DanKearney

Well-known member
Joined
Mar 28, 2017
Posts
67
Location
Black Hawk, Colorado
Howdy All,

Bottom line up front:  I'd like to know if anyone else is running a rig that uses the Ford Triton V10 (2 valve, not the three valve version) and using 85 octane fuel above 5,000 feet?

I recently picked-up a 2000 Gulf Stream Cavalier 19' Class C that is built on a 1999 Ford E350 Chassis.  The owner's manual states to use 87 octane gas.  It also states that it does not recommend using lower than 87 octane gas at high altitude.  It doesn't define high altitude, but I live at 9,200 feet, so I presume that means me.

I picked up the unit in New York and drove it back to Colorado all on 87 octane.  Anywhere east of Colorado gas is available in 87, 89, and 91 octane.  Here in Colorado, its 85, 87, and 91.  I've always run my vehicles here on 85 when they called for 91, because of the altitude and the lower likeliness of having pre-ignition or detonation.

Anyone else in the same situation have problems running on 85 octane?

Cheers,

Dan K.
Black Hawk, Colorado
 
I can feel the difference in the way my vehicles run on cheap gas and I've seen the damage poor fuel causes to the inside if an engine.

my advice ....    Pay for the best fuel now.......or you'll pay for it later.

Spend the extra .004 per gallon,    and save the couple bucks somewhere else.
 
Your engine is designed to run on 87 octane at sea level. It will run just fine at 4000 ft and above on 85 octane. With lower air pressure comes lower combustion chamber pressure and reduced chance of ping. Don't waste your money on octane you don't need.

Richard
 
Yes Richard, that's always been my understanding.  Never had any trouble running 85 octane in any of my vehicles up here.  Since this is the first Ford V10 I've owned, I was just hoping that other owners of the same vehicle might chime in with their own experience.

TonyDTorch,  I do agree with you on "cheap" (low quality) gas.  I usually stay away from non-major brands.  I have to disagree though that 85 octane is lower quality in comparison to the same manufacturer's 87 octane.  The octane rating isn't related to how well the fuel is blended, stored, or transported.  I think it is more important to stay away from off-brands and one-off Mom & Pop stations.

Cheers,

Dan K.
 
I fully understand the physics that allow an engine that runs on 87 at sea level to run at 85 or lower octane above 5000'. However, I'm sure the Ford engineers are aware of this also, so for them to put a note in the owners manual to tell people not to down grade the octane rating at elevation makes me think they know something about the V10 that I don't. When I drove my rig out west, I kept 87 in the tanks all of the time. My situation however is different, as I live in the Midwest and only drove thru Colorado on a one time trip.
 
I always check the octane rating at the pump and use 87 octane.  If it's 85, I'll jump to the next higher grade, usually 87.
 
I'm inclined to sadixon's point of view, except for one caveat: The Ford engineers have no incentive to recommend anything less than 87 octane cause it is your money they are spending to get the higher octane fuel. They know the engine works fine on 87 at all altitudes, so making a high altitude exception for use of 85 is just an extra risk for them. They don't have to worry whether somebody fills up with 85 octane at 7500 ft and then drives down to the lowlands where the 87 is really needed.

Modern computer engine management controls will automatically compensate for pre-ignition, so you should have no problem using 87 at your altitude.  However, if you run at those altitudes all the time, you should also have no problem with 85 octane.  If you don't observe any performance problems with 85, I would use it.  With a previous coach that had the 8.1l gas V8, I ran the 85-octane regular when at high altitude with no issues at all. No knocking, no loss of power, etc.
 
Good, valid points from both Sadaxion and Gary.

So the concept remains gray for me for now.

I think I might stick to 85 octane for a bit and see if there are any adverse results. 

Cheers,

Dan K.
 
Yes,  the computer will detect pre-detonation pinging from contaminated or low octane fuels and adjust the mixture and/or ignition timing as needed to stop this horrible thing from happening inside the engine..... but your engine performance is also adjusted down.

or,  you could put the best fuel available in it,  the computer will allow it to run at it's full performance,  the valves/pistons (and oil) will stay cleaner,  and it may be a bit more powerful, it may give you a bit better millage,  and it may last a bit longer.....(IMO).

I've worked on a lot of engines,  you can definitely see the difference of good fuels and cheap fuels inside an engine.

(and always try and get the lowest possible Ethanol percentage gasoline available ! )

 
It really is simple..... run 85 at higher elevations. If you get some knock, then jump up to mid grade.  Keep in mind, knock may not always be related to fuel itself.  Carbon buildup on pistons can increase combustion ratio and lead to knock condition.  It would be nice if things were simple.  Usually not.
 
Octane is not a measurement of quality, contrary to urban myths. 

I've been taught to always run the lowest octane that won't cause spark knock, anything more is a waste of money.
 
The OP said that he has read the owners manual and it states to use 87 octane regardless of elevation.  If he chooses to ignore the recommendation, why would the question even be asked?

Many want to believe that the engine controls will adjust so that they can run whatever they want.  The control is to protect the engine from low octane fuel, not to adjust for those that ignore the use of proper fuel.  If octane is too low, the adjustments might well reduce (not eliminate) knocking to a low level, but lower gas mileage and performance will result.
 
Octane is not a measurement of quality, contrary to urban myths.
Click to expand...

[Mini-rant] Lot's of luck convincing many drivers of that.  America has become a "more is better" culture, leading people to desire anything with a bigger number associated with it. Products compete on that basis cause the manufacturers know that any claim of "more" will sell.  They advertise something like  "Buy Fungies - 3x more burple than other leading brands" and many people flock to buy it, even though they have no idea what burple is or does, and probably never heard of it before seeing the ad.  "Wow - 3x more. I gotta have that!".
 
The OP said that he has read the owners manual and it states to use 87 octane regardless of elevation.
Click to expand...

That's not quite what was said. "does not recommend using lower than 87 octane gas at high altitude" is not the same as "don't ever use less than 87".  A higher octane gasoline is always safe to use at any altitude and Ford is no doubt concerned that some people may use an under-87 fuel without actually being at "high altitude".  Plus they have cleverly avoided stating what altitude is "high".
 
I've not yet taken my V10 up into the high country. We have gone mostly East and South, so far.
We have two Lincoln Town cars.  a '96, and a 2002.
When we lived back east, whenever we came up to the Denver area, the 96 TC would always turn on the Check Engine Light somewhere around Limon, and it would remain on until we got into Eastern Colorado (Limon Or Burlington were usually a fuel stop. ) Finally, I was reading through the manual, and found  that line that in higher elevations the 87 Octane should be used.

The Sundancer has yet to display any issues running regular (85 Oct) here.
Though the Chassis manual does state the same caution regarding 87 octane at high elevations.
This Spring, if we go over to the Western Slope, I will likely load up with 87 Octane.

 
Gary RV_Wizard said:
[Mini-rant] Lot's of luck convincing many drivers of that.  America has become a "more is better" culture, leading people to desire anything with a bigger number associated with it. Products compete on that basis cause the manufacturers know that any claim of "more" will sell.  They advertise something like  "Buy Fungies - 3x more burple than other leading brands" and many people flock to buy it, even though they have no idea what burple is or does, and probably never heard of it before seeing the ad.  "Wow - 3x more. I gotta have that!".
Click to expand...

You are so very correct, but that doesn't mean a little help in educating the masses is necessary. It's too bad that myths propagate at a much higher rate than a truth.

In a very basic, and primary way to look at the difference between 85 and 92 (or lower vs higher) octane is that the higher octane burns longer and cooler than lower octane.

Here is some interesting reading.
https://www.carthrottle.com/post/engineering-explained-high-vs-low-octane-petrol/

https://www.consumer.ftc.gov/articles/0210-paying-premium-high-octane-gasoline

https://auto.howstuffworks.com/premium-gas-luxury-vehicles1.htm
 
one reason I use 91 octane is my V10 works very hard to get all 26k pounds going everywhere,.. it works even harder going up in the mountains where the air is thinner.

As I step on the gas pedal the computer is adjusting the mixture and timing up to make the most power it can,  until it hears knocks..... Octane rating is basically the anti-knock rating of gasoline.  You may never hear the knocks, but the sensors can and the computer will keep turning down the power until it stops.

it's a lot to ask from a 413 c/i gasoline engine,  so I would like that motor to always run at it's best.
 
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