Octane at altitude and MPG on 6.4L

[agpilot]

Planning a long road trip to CO and Moab from FL this summer.

2 questions:

I know gas stations at elevation in CO sell 85 octane as "regular" and 87 as mid grade. I know 89 is preferred for my '16 but it runs fine on 87. For you CO owners what octane do you run above 5000'

Second question for those who have done long trips - does the bump in MPG make 89 octane worth it over 2000mi?

[OffroadTreks]

Planning a long road trip to CO and Moab from FL this summer.

2 questions:

I know gas stations at elevation in CO sell 85 octane as "regular" and 87 as mid grade. I know 89 is preferred for my '16 but it runs fine on 87. For you CO owners what octane do you run above 5000'

Second question for those who have done long trips - does the bump in MPG make 89 octane worth it over 2000mi?

I've actually done this. And YES you will see an improvement running 89. Better performance and MPG. I pretty much run it exclusively sine we left Florida for the West. You might actually find in CO and parts of Utah them selling 90 and 91. It gets weird. Just don't run 85.

The trucks are OK on 87, but the ECM detunes when you run that. FYI. Although it's most noticeable when you're loaded up or towing. I never really noticed in daily driving around Tampa/Clearwater.

[agpilot]

Thanks Mike,

Just to be clear, are you saying that once I get to CO/UT I should be running 89 or 91 even if that is their "premium" fuel? I agree about the performance at sea level. Here in FL I stopped bothering with mid-grade because I couldn't notice the performance difference.

[Reloaderguy]

Octane level depends on altitude. The higher the altitude, the less octane you need to prevent detonation.

[agpilot]

Octane level depends on altitude. The higher the altitude, the less octane you need to prevent detonation.

This was my understanding as well. That's why the gas stations in CO can get away with selling 85. I think I'll probably run 89 for as much of the trip as I can and if it's reasonably priced in the mountains. If it's expensive for 89 or 90 at altitude I'll just put in 87. Thanks for the info!

[OffroadTreks]

No sorry, that was confusing. I just meant I've seen a lot of weird octane levels in those states, I've seen 85,88,89,90,91,92 and 93 it's weird. I know we stopped at a Loves where they had 4 freaking choices on the pump.

If you're running 87, then 85 at altitude would be the same, so if you're 89 like I tend to do, I think that would be 88 in some places or 87.

Sorry if that was confusing. What reloader guy said is spot though.

[Bill2014]

Here's a lot more discussion on the topic in this thread:

http://forum.powerwagonregistry.org/vie ... ane#p75486

[agpilot]

Thanks, Bill!

[Hammerballs]

A little off topic but does running 91 have any negative effect or is it just waisting money? Does running a higher octane then recommended lead to incomplete detonation like too low of octane leads to pre-detonation? I've never really thought about or researched it much. I know too low is bad and I know I wouldn't run race gas but is there any negative to premium 91/92?

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[OffroadTreks]

A little off topic but does running 91 have any negative effect or is it just waisting money? Does running a higher octane then recommended lead to incomplete detonation like too low of octane leads to pre-detonation? I've never really thought about or researched it much. I know too low is bad and I know I wouldn't run race gas but is there any negative to premium 91/92?

Probably just wasting money.

[verdesardog]

The higher the octane, the less likely to pre detonate but also less energy/volume ratio. Lower octane gas actually has more energy per gallon than high octane so if your engine will run on regular use it!

[Mule]

The higher the octane, the less likely to pre detonate but also less energy/volume ratio. Lower octane gas actually has more energy per gallon than high octane so if your engine will run on regular use it!

This.

Running race gas in an engine that isn't tuned for it doesn't turn it into a race motor.

The best octane to run is the lowest that doesn't det.

There's a lot more to fuel science than most people realize, and octane rating isn't a measure of the fuel's quality.

[Will]

Mine sounds like a coffee can full of BB's if I run 87 because it's tuned to 93 and runs sluggish as shit on 89. Best mpg on 93 with it tuned for 93 out of any other. Even on factory tune, it did not like anything less than 89. I'm in North Florida.

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[DamageWagon]

I get better mileage and noticeably better power with higher octane like 91. To the extent that 91 pays for itself if the cost discrepancy is $.20 between 91 and 87. If I'm in a state like Colorado where the difference is $.50, it makes more sense to run 87 octane.

[Pit Slave]

Here in salt lake area and in Moab, I run ethanol free 88 octane. The best power and fuel economy combined. 05 hemi at around 14+ MPG's. If I run something with ethanol blend, I tend to get 11 MPG's.

Yeah, I smoked 'em, sometimes you just gotta #sendit

[Z's2016PW]

I live in Colorado and the difference between 87 and 91 is about 20 cents. Personally I have never run 85 in the Wagon. Always been 91 octane with a few occasions of 87 being put in. To me it feels like the 91 has more grunt for the Wagon than the 87 does at altitude. Plus I tow so that makes a difference for me.

[ramv]

85 octane here. Have tried higher octane a few times, no noticeable difference.

[OffroadTreks]

Did a little experiment. I filled up the tank 22.764 gallons of 87 ethanol free. Drove up to Cascade today, 176 mile round trip. 16.3 average mpg

[Bill2014]

Did a little experiment. I filled up the tank 22.764 gallons of 87 ethanol free. Drove up to Cascade today, 176 mile round trip. 16.3 average mpg

The "Ethanol Free" is the key!

[Hammerballs]

So is it better to get ethanol free pure gas from some tiny service station that probably isn't turning there fuel over quickly or E-10 from the bigger mainstream station next door that is likely cycling through fuel much quicker? I always heard the "freshness" of the fuel more important then brand (Chevron, Shell, etc). Not sure how that relates to pure gas that you usually can only find at very small stations. I'm going on a 10-day road trip through AZ and CO and I'm looking up all the pure gas stations along our route on pure-gas.org. I've never looked into finding pure gasoline before.

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[OffroadTreks]

So is it better to get ethanol free pure gas from some tiny service station that probably isn't turning there fuel over quickly or E-10 from the bigger mainstream station next door that is likely cycling through fuel much quicker? I always heard the "freshness" of the fuel more important then brand (Chevron, Shell, etc). Not sure how that relates to pure gas that you usually can only find at very small stations. I'm going on a 10-day road trip through AZ and CO and I'm looking up all the pure gas stations along our route on pure-gas.org. I've never looked into finding pure gasoline before.

Ethonal is what effects that "freshness" but gas has a stable shelf life to a point. Actually better than diesel which can get fun microbes that ruin it.

I wouldn't worry about it.