Foxbody Miles per tank?

Mindseye007 · Sep 11, 2025

Noobz347 said:
None, if the engine only requires 87 octane.

There is no BTU difference in the two fuels. The 5b93 contains an additive package that helps prevent compression detonation. Sometimes, a portion of that package includes 10% ethanol. The ethanol will have much larger effect on fuel mileage than the octane rating.

Two pump fuels, one 91 octane no ethanol and one 93 octane no ethanol will be virtually identical in an engine that runs well on the 87.

In your case yours is tuned for 87 correct ?
What is your base timing set at? Mine is tuned for 94 with a sct chip on dyno i got 278 torque and 228 to the wheels. but kinda pointless I guess since I have the stock e7 heads. With an explorer intake, my base timing set at 10degrees. She purrs like a kitten though lots of torque with my 4.10 gears and z-spec 5speed.

Noobz347 · Sep 11, 2025

Mindseye007 said:
In your case yours is tuned for 87 correct ?
What is your base timing set at? Mine is tuned for 94 with a sct chip on dyno i got 278 torque and 228 to the wheels. but kinda pointless I guess since I have the stock e7 heads. With an explorer intake, my base timing set at 10degrees. She purrs like a kitten though lots of torque with my 4.10 gears and z-spec 5speed.

Mine is digitally tuned.
Base timing is 10*
I run a Kenne Bell and roughly 9.8:1 compression and am tuned for 91.

I cannot run 87/89 with the KB at all (at least, I would never do that).

FastDriver · Sep 11, 2025

Mindseye007 said:
How much hp lost with 87 octane over running 93 octane?

I'll never know, but you're really asking how much power is 6* of timing worth. Probably 5-10 rwhp.

FastDriver · Sep 11, 2025

Well, maybe you've convinced me to take it to the track for an 87 octane 1/4 mile, but my ty memory if the Richard Holdener 5.0 books makes me think I'm not that far off. Been wrong before.

Noobz347 · Sep 11, 2025

I wanna play!

[If] you get the full 6*, my guess would also be 10 WHP.

If this is an HCI car with high compression and high lift through free-flowing heads, then half of that before diminishing returns.

85GTStangGuy · Sep 12, 2025

FastDriver said:
Well, maybe you've convinced me to take it to the track for an 87 octane 1/4 mile....

Foxtoberfest would be a great time to get in some 87 octane runs.

Foxbody Miles per tank?

Mindseye007

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Foxbody Miles per tank?

Mindseye007

10 years still blowing strong

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