Gas type?

[ShadowsPapa]

Anything >E15 is dangerous to all aluminum engine components. Alcohol extremely corrosive to aluminum especially under heat. You can run ethanol but it’s long term effects will damage your engine.

We're talking normal ethanol - not E85 here - but then LS aluminum engines run E85 and have for years.

up to 15% safe. They've conducted some pretty intense studies on it, over years time.
What about the flex fuel LS engines - all aluminum? That's all I ran in mine except for when I filled with E85 - and it's like new.

I've been a mechanic since the time it was introduced and never saw any damage - to this day. Why didn't it damage my Kawasaki lawn tractor engine? All aluminum.
We're talking plain 10 and 15% here - not running E85 in 'em.

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[Sal]

And you got that from where - an anti-ethanol site?
Why does ISU say otherwise - up to 15% safe. They've conducted some pretty intense studies on it, over years time.
What about the flex fuel LS engines - all aluminum? That's all I ran in mine and it's like new.
I've been a mechanic since the time it was introduced and never saw any damage - to this day. Why didn't it damage my Kawasaki lawn tractor engine? All aluminum.
Can you explain why it didn't trash my Javelin's aluminum intake and carb parts? If it was so damaging - since I've run it always in everything for decades, why have I never seen damage?

1) I said Ethanol > E15

2) I’m a Certified Fuel Laboratory Technician.

3) Flex Fuel is design to run on up to E85. That’s why is called Flex Fuel. If a vehicle is not design to run on E-20 or greater than you should run it period.

Not sure what level of ethanol your talking about?

just to be clear I’m referring that to running on anything that’s >E15

 

[ShadowsPapa]

1) I said Ethanol > E15

2) I’m a Certified Fuel Laboratory Technician.

3) Flex Fuel is design to run on up to E85. That’s why is called Flex Fuel. If a vehicle is not design to run on E-20 or greater than you should run it period.

Not sure what level of ethanol your talking about?

just to be clear I’m referring that to running on anything that’s >E15

Good clarification - I saw that later.
Why would anyone run on anything other than 15 or less? Where would they even buy it? Not around here for sure.
I'd never run "E85" on anything that doesn't have a yellow cap and specifically states that it's safe. For one thing, the engine isn't designed for that unless there are specific mods made. When we run high performance engines on ethanol (and I mean not gas) there are certain things that must be done. Among them is boost compression up to about 11:1 Carburetors must be totally redone (most are actually a combination of zinc and other alloys - not aluminum, in automotive use) they must be rejetted among other things.
I guess I didn't think anything greater than 15 was even part of the discussion since none of these are flex fuel vehicles.

 

[jurfie]

I guess I didn't think anything greater than 15 was even part of the discussion since none of these are flex fuel vehicles.

That was my understanding of the discussion as well; many gas stations sell gas that "May Contain Ethanol". These blended fuels are usually 10%, but no more than 15% ethanol. E85 is 85% ethanol, and only certain vehicles can use it.

The point is that the JT owner's manual says up to E15 (15% ethanol) is perfectly fine and will not damage your vehicle. Your mpgs will drop with blended fuel, but it will not harm it.

From https://www.fueleconomy.gov/feg/ethanol.shtml:

Ethanol contains about one-third less energy than gasoline. So, vehicles will typically go 3% to 4% fewer miles per gallon on E10 and 4% to 5% fewer on E15 than on 100% gasoline.

 

[ShadowsPapa]

Ethanol is higher octane but contains fewer BTUs per gallon - thus the lower MPG, yes on older engines you can advance the timing a bit and sometimes compensate. My 70 LOVED WalMart's 93 octane ethanol blend. Well, it did before I sold it......... More zip, less ping instances.

 

[Klutch]

I know of only one place to get 100% gasoline in my town and it's at the opposite end of town from where I live. Every other pump has at least 10% ethanol. Funny thing is I run it in my 1970 Mustang Mach 1 without any issues other than a little trouble with hot starts. I also run it in my 1986 Comanche, also carbureted, with no trouble.

A friend of mine has a 1970 Boss 429 Mustang. He says it runs a little better and idles a little higher with 100% gasoline, but otherwise, it doesn't cause any problems.

As for octane, for anyone not aware, higher octane does not mean higher energy or more power. Compared an 87 octane, a 91 octane gasoline simply has additives making is less volatile. That is, it's harder to ignite so it won't detonate under heat and pressure before the spark plug fires. Higher octane is necessary for higher compression engines. This includes turbocharged and supercharged engines which also create higher compression. I have to run premium gas in my Mach 1 because it has 10.5:1 compression (Australian heads). Thus, contrary to popular belief, in a typical engine which does not have high compression, higher octane gas does nothing for you other than emptying your wallet a little faster.

 

[ShadowsPapa]

Octane is the resistance to self-ignition. Longer chains. Same energy content, same BTUs, but it can make more power because the timing can be advanced further. You can run higher compression ratios and advanced timing and get more HP in that way - but it's only because of the resistance to self-ignition.
So if your engine is of the type like the older 4.0 where there was a knock sensor and the timing was backed off by computer if there was knock or ping detected, higher octane fuel would mean it could keep the timing advanced for more power and MPG.
But on modern engines - yeah, no need. It won't do anything for you.
On a car such as my 73 or the 70 I had - if I didn't change the timing for the higher octane fuel, I'd gain nothing at all. If I run the timing for max power then I have to run higher octane fuel. I run for a total of about 36 degrees or so on my 73. As I recall there's where it stopped picking up power on the dyno.
My 70 had higher static compression so I had to keep it cool and run high octane fuel. When I rebuilt it I switched to larger chamber heads to drop the static compression then shot myself in the foot by running a cam that bumped up the dynamic compression. I was right back where I started - having to run 91 at least. My Eagle with 4.0 will run most anything but I find it does like the higher octane a bit better - and cooler weather, too! It really perks with temps in the 40s to 50.
Gas does not lose octane with time - when kept in sealed containers it will have the same octane rating in 12 months as it did when put in said containers.
Higher octane doesn't have more BTUs - it resists self-ignition.
(chambers with good quench or building for swirl can also help prevent detonation)

 

[Sal]

Octane is the resistance to self-ignition. Longer chains. Same energy content, same BTUs, but it can make more power because the timing can be advanced further. You can run higher compression ratios and advanced timing and get more HP in that way - but it's only because of the resistance to self-ignition.
So if your engine is of the type like the older 4.0 where there was a knock sensor and the timing was backed off by computer if there was knock or ping detected, higher octane fuel would mean it could keep the timing advanced for more power and MPG.
But on modern engines - yeah, no need. It won't do anything for you.
On a car such as my 73 or the 70 I had - if I didn't change the timing for the higher octane fuel, I'd gain nothing at all. If I run the timing for max power then I have to run higher octane fuel. I run for a total of about 36 degrees or so on my 73. As I recall there's where it stopped picking up power on the dyno.
My 70 had higher static compression so I had to keep it cool and run high octane fuel. When I rebuilt it I switched to larger chamber heads to drop the static compression then shot myself in the foot by running a cam that bumped up the dynamic compression. I was right back where I started - having to run 91 at least. My Eagle with 4.0 will run most anything but I find it does like the higher octane a bit better - and cooler weather, too! It really perks with temps in the 40s to 50.
Gas does not lose octane with time - when kept in sealed containers it will have the same octane rating in 12 months as it did when put in said containers.
Higher octane doesn't have more BTUs - it resists self-ignition.
(chambers with good quench or building for swirl can also help prevent detonation)

This is a perfect explanation. I was about to write a whole thesis on the difference between 87 and 93

 

[WXman]

And to throw another monkey wrench in the works... there are a LOT of Pentastar owners who've noticed what sounds like pre-ignition while under load. That classic "pinging" that sounds like a coffee can full of marbles. I myself have noticed it on my JLU and JT both. It typically is noticeable at around 35 MPH while pulling up and down hills on rural roads. Faster than that and the wind noise gets too intense to hear it. But, it's been a commonly discussed topic with these Jeeps.

The question has been.. is the compression too high for the 87 octane fuel? Is FCA being really conservative with their fuel recommendation?

 

[ShadowsPapa]

And to throw another monkey wrench in the works... there are a LOT of Pentastar owners who've noticed what sounds like pre-ignition while under load. That classic "pinging" that sounds like a coffee can full of marbles. I myself have noticed it on my JLU and JT both. It typically is noticeable at around 35 MPH while pulling up and down hills on rural roads. Faster than that and the wind noise gets too intense to hear it. But, it's been a commonly discussed topic with these Jeeps.

The question has been.. is the compression too high for the 87 octane fuel? Is FCA being really conservative with their fuel recommendation?

Well first I want to say that although I've done tons of study and written articles on fuel, detonation and its causes, pre-ignition and so on - I've never known a fuel tech before - certified no less and am glad there's one around...................

OK, here's one that I hope doesn't offend anyone - pre-ignition and detonation are two different things and totally different causes!
Pre-ignition happens when something lights the charge BEFORE the spark plug fires - thus the PRE part. Before ignition. There is something hot in there, carbon build-up, a spark plug that's too high a heat range, engine running hot causing sharp edges on the chamber to be hot, the valves maybe are worn or have sharp edges and are glowing, that sort of thing - think "glowing ember" in a sense. PRE-ignition means the charge is already burning when the spark plug fires.

Detonation is when the pressure of compression is high and then the the charge lit by the spark plug causes the pressures to rise even higher and faster and the flame front of the burning charge advances like a brick wall against the unburned charge sitting in a corner so to speak and the unburned charge is compressed to the point that it self-ignites AFTER the charge is already lit by the spark plug. Now you have the normal flame front advancing and the flame front from the gases that ignited from the heat and pressures of compression and combustion heading toward each other and the collide - BANG, you literally have a sonic boom in the chamber - that sonic boom resonates in the engine causing the "ping" sound. (I wonder if there was a ping sound billions of years ago - doesn't matter, no one heard it if there was)

These days pre-ignition should be rare - especially on engine with low miles, very low oil consumption (meaning low carbon build-up) and hopefully lack of sharp edges. A spark plug of the wrong heat range with an engine running hot- maybe.
Detonation - I could see that if the computer isn't backing the timing down and the engine is running HOT or under heavy load. If the chamber design doesn't work to avoid unburned gases being cornered and sitting STATIC, meaning not moving......
Quench means the piston coming up gets really close to the head and shoves unburned gases outward causing them to mix and swirl, preventing some from sitting around. Swirl is where the design keeps things moving in there - the incoming air doesn't just come in and sit- it's forced to move around in a sort of circular motion - swirl around, keeping things mixed up.

So if the engine is running hot, under very heavy load, as if it's in too high a gear (LUGGING), or there have been modifications made...... maybe, but in an engine that's not been modified, with good spark plugs of the correct heat range and the engine is not being lugged or isn't running hot - the computer should be backing timing off and compensating.
It takes TIME to burn a charge - faster RPM means you have to light it sooner so that peak combustion pressures take place about 16 degrees or so ATDC. To keep that happening you light it sooner at higher RPM - but if you advance it too far you actually achieve too much pressure as the piston is still rising, or you cause detonation by making that peak pressure too early forcing the unburned portion to self-ignite.
In other words - this could be driver error (lugging, overloading, ignoring a hot engine or mods they thought were cool but are really destructive) or a computer that's not backing things down - and that could be a sensor issue among other things - assuming these things still run sensors in the block or head to detect such things.

 

[mazeppa]

I have access several local station with ethanol free fuel for my vehicles that I use most of the time, but I if only had normal ethanol available I would use it with no worries. On my STIHL and Husqvarna 2-cycle engines I will only use ethanol free premium (93) for my oil/fuel mixture.

 

[ShadowsPapa]

I have access several local station with ethanol free fuel for my vehicles that I use most of the time, but I if only had normal ethanol available I would use it with no worries. On my STIHL and Husqvarna 2-cycle engines I will only use ethanol free premium (93) for my oil/fuel mixture.

Those teeny fuel lines, filters and carburetors, such as they are on those little engines, those are picky as heck. I've seen some of the warranties that are very specific - no ethanol.

 

[TrailHiker]

Well. AvGas (aircraft fuel) is ethanol free, I use this in all my small engines, and in my larger Lawn Tractor engine in the winter, where it sits more than being used.
Cheers

 

[BLK HOLE]

Anything more than 87 is a waste of money on a stock 3.6.

 

[Lou3.6]

We've got 87, 89, 93 around here.

I swear they're putting ethanol in our gasoline now, because my MPGs are lower for no other reason, and when I start the truck on a cold morning I can smell it.

Well, if your smelling it . . . take a closer whiff . . . make sure it's not some of that Fine Kentucky Bourbon they've not used as an Additive instead of that crap ethanol !

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