What octane are you using?

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Mar 11, 2019 | 01:38 PM

#16

don123

Laughing Gas

Joined: May 2006

Posts: 1,047

Likes: 6

From: Massachusetts

I’ve tried 93 and 89 octane and there’s not benefit. So it’s 87 every fill up.

Mar 11, 2019 | 10:56 PM

#17

acadianbob

Cargo Master

Joined: Jan 2004

Posts: 2,424

Likes: 697

From: Minnesota

Quote:

Originally Posted by rvpuller

I was in that mind set until last fall when heading east pulling our rig, my mileage was not what it's been I'm the past and when I filled at a Flying J it dropped even more, I started using top tier gas after that and it when back up over what I was even getting before and I could feel a little more power so for a few cents more a gallon I'm staying with top tier if available.

Denny

And Top Tier has better additive packages to keep your engine cleaner on the inside. I buy Top Tier whenever possible too.

Mar 12, 2019 | 06:43 PM

#18

govols60

Freshman User

Joined: Jul 2018

Posts: 37

Likes: 0

87 octane always top tier from a high volume store to ensure
fresh clean fuel

Mar 18, 2019 | 10:57 AM

#19

crewzer

Logistics Pro

Joined: Apr 2000

Posts: 4,334

Likes: 306

From: Mills River

Quote:

Originally Posted by Chuck's First Ford

top tier is best.

but over 7,000 feet.... air is much thinner.. try running for 5 minutes..
the higher octane... does nothing.. as air is thinner.... and Needs LESS fuel to maintain 14.7 to 1...
fuel injection can not make more air... unless a supercharger or turbo is helping..''

your truck, your money, your trip.

My understanding is that there’s more to this story. Specifically, high elevation air pressure is lower, resulting in a lower pressure air-fuel mixture that burns slower. A partial “cure” is to advance the ignition timing to compensate for the slower burn, but this can lead to pre-ignition / ping / knock if using lower AKI fuel. This is why Ford says to not use less than 87 AKI fuel, even at higher elevation.

You can probably use 85 AKI at higher elevation, but the ECU will likely not dial in the optimal ignition timing advance.

Back in the “old days”, I used to manually advance my cars’ distrubutors when driving over the Rockies. The rule of thumb was an extra one degree of advance for every 1,000 feet of elevation. Our 1986 Suburban had different ignition timing settings for sea level and “High Elevation”, which was 5,000 feet and higher.

HTH,
Jim / crewzer

Mar 20, 2019 | 10:25 AM

#20

ssls6

More Turbo

Joined: Dec 2003

Posts: 534

Likes: 168

From: Park County, CO

It has to do with cylinder pressure....Your down on power at high elevation because the cylinder pressures are lower (fixed compression ratio against thinner air). The lower the absolute compression, the lower the octane needed. Turbo's negate this effect so you should really stick to 87 if called for.

Mar 22, 2019 | 08:33 AM

#21

saratoga2011

Laughing Gas

Joined: Nov 2010

Posts: 794

Likes: 255

I try to use 89 or ethanol free fuel whenever possible (most of the time I don't tow anything). There is a noticeable difference, especially in the heat.

When outdoor temps are high (talking mid-high 90's) and I use 87, you can literally feel the truck pull timing when you take off from a stop. I go to accelerate, the sound of the engine changes, it lugs and makes a blaaaaaaaaah sound until it shifts to 3rd. I also notice the idle kicks up to 750 or so when stopped in these temps.

Using 87, no-ethanol 89, or 93, it does not retard timing to where it's noticeable.

Mar 27, 2019 | 04:35 PM

#22

govols60

Freshman User

Joined: Jul 2018

Posts: 37

Likes: 0

I see no difference in 87 vs 93 octane as far as mileage
I have tried two full tanks of 90 octane ethanol free and noticed a 2mpg gain. But cost vs increase in mileage🤔
not worth the cost for the 2 mpg gain