Had about 1/2 tank of 86 octane dino juice, (almost) topped up with 93.
I'm surprised at how much smoother and peppy the old 5.0 is!
What magic happened?
I'd prefer to not spend the extra on Premium, or do a special blend.
Thoughts?

 

I have no proof, but have heard most higher octane fuel at the pump does not have ethanol in it. Some may have, some may not. You will get better fuel mileage with a non-ethanol fuel.

 

I have not heard that about the higher octanes?

What I think it is you may just think it is for the extra money you put into the tank as I cant see adding 1/2 a tank would make that much of a difference but????
OR
The knock sensor is not hearing spark knock and can advance the timing more and that you will feel.

Dino juice, do you also run Dino Syrup and if the motor is hard to start, spray Dino Fart in the carb
That guy is great on YouTube https://www.youtube.com/@TarylFixesAll
ps I was a grass rat yesterday
Dave ----

 

Back when I had my Bronco in the early 2000's I would, on occasion, put half tank of "racing fuel" (same Sunoco fuel NASCAR used) in the tank then top it off with super. That 351W ran like a "raped ape" when I did that. I don't remember if ethanol was a thing back then...

 

Having pumped fuel into a 1986 5.0 EFI for thirty-eight years I would agree with this statement. I chose mid grade 89 octane rating all those years because the extra cost was a wash when fuel mileage was considered. The truck would go the same distance per dollar spent. And, even when new, the engine would ping under a heavy foot on 87 octane fuel. With 87 you'd hear the ping and instantly the power would fall off.

This is more pronounced in my 1997 supercharged Buick Riviera. 21/22 mpg on premium (93 octane) or 18 mpg on 87. Plus it runs like crap on the 87.

Also, when "talking octane", one should consider that "octane" is a hydrocarbon compound while octane "rating" is a completely different thing. Octane rating is a gauge of the fuels ability to resist unwanted detonation under compression.

Octane rating can be raised by a number of compounds including ethanol. Back in the day refiners used tertraethylead. 10% ethanol raises the octane rating of regular unleaded gasoline by about three points. Commonly, premium fuel has its octane rating increased by adding reformed naptha.

 

Dave, here is some research I did on the subject a few years ago. The discussion was primarily how ethanol and octane rating affected carbureted vehicles, so not all of it was applicable for fuel injection:

https://www.ford-trucks.com/forums/1...g-and-you.html

Note how ethanol increases the octane rating of fuel. Most premium fuel has more ethanol, not less.

Post #5 above brings up an interesting point about naphtha being used to increase octane. I’m not sure if this means instead of ethanol, or in conjunction with it.

The other interesting point is to consider miles per dollar, not necessarily miles per gallon. Thank the knock sensor. It is an amazing invention that allows automatic regulation of ignition timing for maximum efficiency and performance.

 

10% ethanol in everything around here. I have to make a trip up to the Snohomish Co-Op and jocky with the horse and cow owners at the pumps for 'less stuff in it, but more expensive' ethanol-free gas for my Italian fiber-tanked bike that expands as it soaks up the ethanol, and for my small engine outdoor machines.

 

Hmmm another message board thread has reports that the knock sensor is no longer available. Now, my backyard mechanic brain (Warning! Warning!) is t-t-thinking about inspection and maybe... cleaning the bugger?

 

From your description, I'd say your knock sensor is performing perfectly. IIRC, it's a sealed unit with some special material inside that resonates when exposed to the same frequency as engine knock. When triggered, it magically generates a voltage as an input to the computer. There's nothing to clean, other than the connector. Not much to inspect, other than looking for wire damage and security of mounting.

Back to the lack of power on low octane fuel. I wonder if you had some mechanical variance, such as non-spec spark plugs. If in a range hotter than stock, they'd be more prone to pre-ignition. Or maybe timing in general was off. The higher octane fuel helped mask the issue, and the knock sensor responded accordingly.

What about the low octane fuel you were previously running? Are you buying a quality name brand, preferably from a high volume source so it's not going stale? Or are you buying from whichever Stop 'n Rob convenience store has the cheapest price that day?

By chance do you live close to, but not in an area that mandates special seasonal fuel blends to reduce pollution? When refiners switch formulas, the distributors typically unload the leftovers in nearby areas with no such mandates. You may have been unknowingly running old fuel not exactly optimized for conditions. The improvement you saw may not have necessarily been from the octane increase.

 

Yeah, I'll leave it alone.
Seasonal fuel formulas do change around here, but I've never experienced this through the years. Timing is per specs, (SPROUT addressed), so still curious about the nice drivability!

 

Reformed naptha. Re-formed naptha is derived from running heavier naptha, unsuited for specialty products, through a Platinum Catalytic Reformer which breaks down this naptha into the compound blended into the gasoline. Turns an otherwise unuseful compound into something useful.

Remember Shell gasoline with platformate? In that case platformate was a proprietary term for the product derived from their Platinum Catalytic Re-forming process.