I'm helping a friend rebuild a 4.6L Windsor in a 97 F150 and am looking for feedback on what fuel grade is best to use. Ford apparently recommends regular and I'm wondering what the reasoning is behind that. I'm a fan of premium fuels myself. Are these engines 'tuned' such that the don't run well on premium? Any info would be appreciated.
Cheers.

 

Unless you tune for it, premium is a waste of money. Use the recommended 87. If you WANT to use premium, don't do it without getting it tuned for it.

 

The stock engine is designed to run on 87 octane per owners manuel.
Technically there are a lot of parameters involved.
Some of which is combustion chamber shape,
Compression ratio,
Camshaft timing,
Vehichle weight and other parameters.
The use of higher octane fuels slows combustion flame speed such that the ignition would be a bit to late for best use of those fuels.
This becomes a waist of money for little to no advantage.The computer will shift to some degree over time as the crank rotation time difference is detected, but still not enough to make much difference.
Your thinking is of old times back in the carb days that doesen't relate much to modern fuel injection.
Thanks for asking the question. I'm sure others had the same guestion.
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It's much like the old position of using heavey oils thinking it will help the motor live longer. This thinking does not apply to modern Ford ohc motors and improved oils, and will cause wear over time that should not occur until much later in the engine's life.
Good luck.

 

However, *IF* you tune for high octane, then there will be performance and economy advantages. With today's fuels, I don't think high octane runs any cleaner as long as you use a "top tier" gas.

 

Good info - makes sense. Thanks guys.