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dkoldman · 12-02-2021, 01:41 PM

Quote:

Originally Posted by sportcoupe

I don't believe I brought up internet engineers. I typically wouldn't make that type of statement, being myself an actual engineer

1987 is pretty much the switchover year from carbs to computer controlled fuel injection overall, at least for GM. Of course there are outliers but this is when the old carb was phased out and modern injection was born. Of course fuel injection was before 1987, but it was clunky. And todays fuel injection is even better of course.

87 is the minimum rating required by Ford. It is not an absolute. If I see 85 and 91, guess what? I am pumping 91 because I am not staying, just passing through and my tank is huge. Its all about smiles per mile, not dollars per mile in my RV.

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My Ford Manual for 2018 F53 says the 87 Octane is the minimum rating recommended. It never says to not use, but does say if you do use, engine damage may not be covered.

By contrast the same manual does say to not use Ethanol blends greater than 15%.

With all that said I think using 91 is no question better than 85 or 86. But the same is true that 91 is better than 87. But that is your option; although perhaps not the question.

In my view 85 & 86 is made for a reason, above a few poster stated it's technical function in engines in high altitudes. As long as it is available I will always use, unless my manual says that I can't use. That would be a big statement for Ford to make; and I doubt they ever do. For the record, I have never bought 91 octane in my life, not because of a manual or gas performance, but because of price. I have also never had an engine issue related to gas. I welcome not only 85 or 86 when it is available; but also the break in price that comes with it.

Just so you know, my tank is 80 gallons; 98% of the time I buy gas north of 1/4 tank; so most times I am buying 55 gallons of the cheapest gas available at the pump that is NOT ethanol. I do the latter 100% without a thought. I would say 99% of all my gas is 87 Octane and 1% 85 or 86 Octane in the big picture. No big deal for me.