Which octane for new Ford V-10

On our 99 we did the same. More 91 than 87

Running 87 since new. Towing or not. Runs fine. 7.5mpg not towing, 7.3 towing.

If your vehicle is running correctly (no Check Engine Light) chances are you won't be able to tell the difference between 87 and 91. If you use less than 87 octane, the CEL will usually come on especially when towing or in hilly terrain and you will lose some performance.

EDIT: On the other hand, under some conditions, if you work the engine very hard and it gets hot, using higher octane fuel may help restore lost power if due to pre-ignition/detonation. It generally won't INCREASE power, only restore what should have been there. As your engine ages, carbon builds up on the piston crowns and cylinder heads causing the compression to increase. This can cause pre-ignition/detonation. Usually it gets offset by engine wear. Mostly leakage (compression) past the piston rings. As others have said, electronic spark control usually controls everything behind the scene, but not always.

Chum lee

Some areas in the West, at higher altitudes, sell 85 octane fuel. My vehicle runs fine with it. The electronic control module on most vehicles will adjust for any of the fuels on the market today, as well as outside conditions, including altitude and temperature. That said, the best advice is to follow what the owner's manual says should be used. If it says 87, then I would use it. Spending the extra for 91 may not only cost more, it probably does not provide any noticeable difference to the way your engine runs.

87 is the stock specs for the fuel for V-10, however my 08 Bounder with the V-10 does perform better with the mid-grade 89 octane fuel and gets better MPG, I know some are going to say that's nuts but it really does, maybe because I have the Banks Power Pack system and the Five Star Tuning I am not sure but it just runs better.


Sometimes it has a very lite ping with the 87 but never with the 89..

The engine computer adjusts the timing as necessary to avoid (most) pinging. Because of this, it is conceivable that, at least under some conditions, you may get better performance or mileage from higher octane gas. I do suspect that, in general, any mileage improvements would not be sufficient to bring about a net savings in fuel costs, but that's just a guess.

I use 87. My V10 seems to run just fine with it. I spend enough on gasoline for it without springing for the higher cost options.

My Ford Motorhome Chassis manual says to use 87, and nothing lower. If your options are 85 or something higher go with the higher. In the same section, it states that IF you have an EcoBoost engine and towing, then you may benefit from a higher octane than the 87.

Whatever the owners manual says.

I would run 89. Maybe a tank of 91 or higher if you will be running higher RPM`s in the mountains. My V-10 actually ran better on 93 before I had the 5 star tune. I now have the 5star tune with an 89octane towing tune. runs great and I get .5 mpg better.

I would test out different octanes and see which one does best!

You bought a Ford because you trusted them. Why wouldn’t you trust Ford on fuel?