Comment regarding gasoline and altitude

[pshipsey]

I lived in Colo when I first got my class C, 24' camper.
It's powered by a E350 SuperDuty
v10. She runs well.
Just drove from the UP to Colorado. When I excited the freeway, my camper began hesitating as of not getting gas. Super concerning
I spent the week in town, driving around, no issues.
I left Colorado, and when I got to NE it started up again. Kinda feels like a fuel pump going out. But it isn't.
I googled last night and saw that it might be 85 octane gas and the altitude. Spent the night in NE and put in 1/2 tank mid-grade octane in the morning.
Problem solved.
I'm posting partially to inform others in the group of high altitude effects, and to get conformation re the altitude issue.
 Thanks

 

[Derby6]

I had a '95 F350 that did that a few times. I know mine was altitude. Truck was bought in SLC and it happened in mountains a few times.
I think it was I-80 parley canyon where I was descending (westbound) and truck just would not accelerate for a 1-2 mile section. Was weird.

That being said yours could be something different. Maybe vapor lock if things getting too hot under hood?

 

[Mark_K5LXP]

Vapor lock ended with the advent of in-tank fuel pumps. The flaw in the octane/altitude theory is neither the altitude or octane changed fast enough to make that plausible for brief hesitation then self resolving. Octane doesn't have that marked of an effect on performance. Crappy gas could though. Quite likely this event won't set a code but you can observe the event via OBD. If this becomes a pervasive problem then monitoring engine parameters would be the way to narrow the cause.

Mark B.
Albuquerque, NM

 

[bigbAZ]

Mark, what about the knock sensor retarding the timing, wouldn't you feel that if your foot was in it?

 

[Gary RV_Wizard]

85 octane gas is fine to use at higher altitudes (like Colorado). But you probably didn't have 85 octane gas wen you arrived there from the UP, right? No reason for hesitation upon arrival.

Presumably you filled up with 85 octane gas while in COL, so maybe not so good when descending to lower altitude. Western Nebraska is still 5000 ft, but drops as you head further east. That will cause some performance loss and maybe even a bit of engine knock, but any V10 should auto-adjust to the 85 octane gas. Just add some 87 or higher at your earliest opportunity.

 

[Mark_K5LXP]

Knock happens primarily at mid throttle and cruise RPM. Put your foot in it and between fuel and timing it usually goes away. When EFI became common the myth was sold that knock sensors would eliminate ping. I had a 4.6 high compression ford that didn't get the memo. If I didn't run 90+ octane it sounded like a box of rocks. I know with my more current cars with variable valve timing they seem octane immune even maintaining good economy so I think it's engine specific. But presuming knock is the problem I'm not sure the incremental shift in timing would result in driveability issues. Something else is going on.

Mark B.
Albuquerque, NM

 

[pshipsey]

85 octane gas is fine to use at higher altitudes (like Colorado). But you probably didn't have 85 octane gas wen you arrived there from the UP, right? No reason for hesitation upon arrival.

Presumably you filled up with 85 octane gas while in COL, so maybe not so good when descending to lower altitude. Western Nebraska is still 5000 ft, but drops as you head further east. That will cause some performance loss and maybe even a bit of engine knock, but any V10 should auto-adjust to the 85 octane gas. Just add some 87 or higher at your earliest opportunity.

 

[pshipsey]

Agreed. Before arriving in Colo, I filled the tank in southern WY (possibly 85) and then filled it before leaving Colo (def 85). And yes, the higher octane gas solved the issue.
Good to know

 

[pshipsey]

Vapor lock ended with the advent of in-tank fuel pumps. The flaw in the octane/altitude theory is neither the altitude or octane changed fast enough to make that plausible for brief hesitation then self resolving. Octane doesn't have that marked of an effect on performance. Crappy gas could though. Quite likely this event won't set a code but you can observe the event via OBD. If this becomes a pervasive problem then monitoring engine parameters would be the way to narrow the cause.

Mark B.
Albuquerque, NM

thanks, Mark. and way above my pay grade

 

[Kirk]

Before arriving in Colo, I filled the tank in southern WY (possibly 85) and then filled it before leaving Colo (def 85). And yes, the higher octane gas solved the issue.

While 87 octane is generally recommended for a Ford V10, at higher altitudes, you may be able to use 85 octanes without issue due to the lower air density. In my 18 years living in WY, I can't recall ever seeing 87 octane for sale as regular gasoline. It's always best to consult your owner's manual and listen to your engine's performance. I drove a Ford V10 powered motorhome all over the country and the onboard computer took care of the variations in altitude. My owner's manual for the F53 chassis did state that 87 octane should be used at all altitudes, since it isn't available in most of the Rocky Mountain areas, I didn't always do that and never experienced any problems. You might be wise to at least have your RV checked for any error codes.

 

[Larry N.]

Like Kirk, I don't recall ever seeing 87 octane for regular at high altitudes. Around 3K some places use 86 octane, and by 5K it's usually 85 octane, which never caused us a problem on a car, pickup or our F-53 V-10 RV, even at 11K ft through Eisenhower tunnels.

Granted that a few high performance cars (Maserati, etc.) might need to go to the mid- or high- grade of unleaded, but most should do fine with the 85 octane. That's been true ever since unleaded came around and since they mandated ethanol for "emission control" in our area.

 

[DonTom]

, I don't recall ever seeing 87 octane for regular at high altitudes.

CA has 87 octane at 7K' elevation, no 85 available, IIRC.

There is no reason to not have 87 and above in CA at higher elevations when you can be at sea level in 60 minutes. This RV has an 80-gallon fuel tank. I won't put in a full tank of 85 octane at 7,000' when most of that same gasoline will soon be at sea level.

-Don- Redcrest, CA (166' elevation right here)

 

[Larry N.]

CA has 87 octane at 7K' elevation, no 85 available, IIRC.

Since I've never been to a high altitude gas station in CA, and I have been to high altitude stations in CO, NM, UT, MT, Western KS and Western NE my above statement stands.

 

[DonTom]

Since I've never been to a high altitude gas station in CA, and I have been to high altitude stations in CO, NM, UT, MT, Western KS and Western NE my above statement stands.

Then you have not seen much of CA.

" 16 peaks exceed 4000 meters (13,123 feet) elevation and 46 peaks exceed 3000 meters (9843 feet) elevation."

And of course, CA also has the lowest points.

CA has everything and then some.

Especially taxes .

-Don- Redcrest, CA (Elevation=88' says my GPS).

 

[Isaac-1]

One can talk as much as they want about theory, but sometimes reality has a way of interfering, I have experienced this same thing when driving in Wyoming with the 8.1L Vortec gas engine in my motorhome. In fact I am in Wyoming just outside Cody on my way to Yellowstone right now, and sure enough after starting to get over 4,500 ft or so on the drive up here after filling up with 85 octane in Colorado it started acting up again, this issue went away after topping up about half a tank of 87 octane. In my experience with my coach it is just not happy with 85 octane, is better with 86, particularly when some 87 is mixed in.

 

[DonTom]

One can talk as much as they want about theory, but sometimes reality has a way of interfering, I have experienced this same thing when driving in Wyoming with the 8.1L Vortec gas engine in my motorhome. In fact I am in Wyoming just outside Cody on my way to Yellowstone right now, and sure enough after starting to get over 4,500 ft or so on the drive up here after filling up with 85 octane in Colorado it started acting up again, this issue went away after topping up about half a tank of 87 octane. In my experience with my coach it is just not happy with 85 octane, is better with 86, particularly when some 87 is mixed in.

IMAO, in modern vehicles, we should all disregard elevation and simply use whatever our owner's manual says. I have yet to see a modern engine owner's manual that says to use less than 87 octane anywhere. Let the vehicle's sensors and computer take care of all of it, even when at 20,000' elevation--no exceptions!!!

This RV says use 87. If I am in Denver, I will still use 87 even though that could be considered midgrade in Denver and lowest-grade gasoline in CA.

Page 42 (2021 Ford 7.3L):

"Some fuel stations in high altitude areas offer fuels posted as regular unleaded gasoline with an octane rating below 87. The use of these fuels could result in engine damage that will NOT be covered by the vehicle warranty."

These days, the design is for varying elevations with the same grade of gasoline everywhere. Do not screw with the modern engine design by using less octane at ANY elevation.

-Don- Redcrest, CA

 

[TheBar]

There might have been confusion at the pump. E85 gas sounds like 85 octane. But it is between 51% to 85% ethanol and is commonly called flex fuel. It is available at many gas stations now. If the engine isn't designed for it that can cause big problems.

 

[Isaac-1]

No confusion on my part, Regular Unleaded rated either 85 or 86 octane

 

[DonTom]

There might have been confusion at the pump. E85 gas sounds like 85 octane. But it is between 51% to 85% ethanol and is commonly called flex fuel. It is available at many gas stations now. If the engine isn't designed for it that can cause big problems.

Yeah, they picked a very stupid name for the E85. If it were up to me, I would label it as "FF" and no number at all.

But it makes no difference to me, I would never use 85 anything in any of my vehicles at any elevation.

-Don- Redcrest, CA

 

[John From Detroit]

i do agree with the use higher grade for reasons stated by ithers. Stations sell lower octane for cars that will likely never go "Down the mountain" RVs well That is exactly where they are going. Get the "Mid" grade it is usually 87.