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Towing with new 6.4L

raven_dt said:
Don't use 85 octane in your modern vehicle. Here is the actual science behind it:
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That really only applies to forced induction engines (like the eco boost in the F150 he’s talking about) as a forced induction engine is going to have the same absolutely pressure at altitude as it does at sea level (until you exceed the compression ability of the compressor of course). For a naturally aspirated engine the higher you go in altitude the lower the air pressure is, and thus the lower the absolute pressure before combustion is, reducing the octane rating required to prevent pre-ignition.
 
jsalbre said:
That really only applies to forced induction engines (like the eco boost in the F150 he’s talking about) as a forced induction engine is going to have the same absolutely pressure at altitude as it does at sea level (until you exceed the compression ability of the compressor of course). For a naturally aspirated engine the higher you go in altitude the lower the air pressure is, and thus the lower the absolute pressure before combustion is, reducing the octane rating required to prevent pre-ignition.
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That's not what I took away from it.
 
jsalbre said:
... reducing the octane rating required to prevent pre-ignition.
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Incorrect, higher octane is required to prevent pre-ignition. It's just you don't have to use higher octane at altitudes it would be a waste of money. Same as it's a waste of money to use 91 (in most cases) if engine is designed to run on 87
 
MEGA HO 3500 said:
Incorrect, higher octane is required to prevent pre-ignition. It's just you don't have to use higher octane at altitudes it would be a waste of money. Same as it's a waste of money to use 91 (in most cases) if engine is designed to run on 87
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I think that’s exactly what I said?
 
The relevant portion of the video (for those that don't want to sit thru 10 mins of the math behind why you *shouldn't* use 85 octane in a modern EFI ICE) just skip to 11:05 for the statement from the DOE saying essentially the same thing: don't use 85 octane in modern engines.
 
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jsalbre said:
Higher altitude = less pressure = lower octane rating required.
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No such thing as lower octane rating required.
"Minimum octane rating required" however is a thing, meaning you could use any octane higher than minimum.
Hell they still sell 76 MON (about 80 RON) fuel in ex Soviet countries as they still drive cars with 7:1 CR. You could run them on regular or premium fuels too it's just gonna be a waste of money as such engines won't take advantage of more expensive fuels due to their low CR, same as running a modern NA car at altitude - could use lower octane but it's NOT REQUIRED.
 
Dave01 said:
He meant turn off the dash calculator. Which I don't believe you can do, I think he meant simply go to another screen so the low mpg numbers aren't staring him in the face.
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I know, I know... I just needed to insert my as$hole comment for the day. Plus, that guy needs it from time to time. :)
 
gimmie11s said:
I know, I know... I just needed to insert my as$hole comment for the day. Plus, that guy needs it from time to time. :)
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No, I don't think you understand. What he really meant was drop the gear selector to 4th to redline the engine, then push the stop button to turn off the engine. :D

It took me 3 weeks of owning mine before I realized I could shut off the lane warnings, so I'm a bit slow on the uptake!
 
MEGA HO 3500 said:
No such thing as lower octane rating required.
"Minimum octane rating required" however is a thing, meaning you could use any octane higher than minimum.
Hell they still sell 76 MON (about 80 RON) fuel in ex Soviet countries as they still drive cars with 7:1 CR. You could run them on regular or premium fuels too it's just gonna be a waste of money as such engines won't take advantage of more expensive fuels due to their low CR, same as running a modern NA car at altitude - could use lower octane but it's NOT REQUIRED.
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Maybe not per the manufacturers, but it definitely checks out. I’ve run plenty of logging on my previous NA engines (two Jeep 3.6s, a Subaru 2.5, and a Ram 6.4) on 85 when I was living at 9k feet and no knock or timing pull at all when at altitude, including towing in the heat.

You do of course need to be careful not to step down octane if you’re going to transition from high altitude to low altitude..
 
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Redfour5 said:
"That’s because it’s a click-bait YouTube video designed to make money from ads."

These are NOT mutually exclusive concepts.
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Exactly. If a video or article uses a title like “Never blah blah blah!” And has a giant “Don’t!” In the preview image, it’s clickbait. Non-clickbait uses actually descriptive titles, like “85 octane may be bad for your engine”, but that’s not nearly as exciting, or “scary”, so less people click on it.
 
jsalbre said:
Maybe not per the manufacturers, but it definitely checks out. I’ve run plenty of logging on my previous NA engines (two Jeep 3.6s, a Subaru 2.4, and a Ram 6.4) on 85 when I was living at 9k feet and no knock or timing pull at all when at altitude, including towing in the heat.

You do of course need to be careful not to step down octane if you’re going to transition from high altitude to low altitude..
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Yep, did many a trip from Kansas City to Denver/mountains above. Going west, at Limon 85 coming back 87 and never forget... It's interesting, but in MT, where I live now, no 85 so no question in my 2500 Hemi but I don't put 85 in even if I have the opportunity... I remember going west with my parents pulling a pop up as a kid year after year... Dad had a 64 Dodge station wagon with a 440 wedge engine and hydraulic clutch. It was an odd one they were having a hard time selling so he got a deal... It was a beast of a car but, he would have his mechanic do a high altitude tune on it every year when we headed west... Since he was a Jr. High School principal, we would take off the day after he closed his school and stay out for as long as 60 days, usually 30 to 45 days...

I was never sure what that high altitude tune meant or did. But, dad did tell me about the octane difference and how the altitude made an 85 act effectively like an 87 at low altitude, but back in those days, it was ALL carburetors all the time, non of that fancy smancy fuel injection stuff...
 
jsalbre said:
Exactly. If a video or article uses a title like “Never blah blah blah!” And has a giant “Don’t!” In the preview image, it’s clickbait. Non-clickbait uses actually descriptive titles, like “85 octane may be bad for your engine”, but that’s not nearly as exciting, or “scary”, so less people click on it.
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Ahhh, marketing an age old concept in the digital age... "BUT WAIT!" My wife and I when watching the tube can watch certain commercials, look at each other and say "BUT WAIT!... and then it comes usually with something "free" or a second one free and all you gotta do is pay for the shipping...

Ahhh, marketing pukes will end up ruling the world... Remember before all the truck manufacturers taking up the SAE J2807 standards for towing? My goodness, the marketing pukes said my 2500 would have been able to tow a loaded semi across the country up 20% grades and hardly break a sweat.... The marketing pukes were NOT happy about the engineers winning that one...finally...
 
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