Which octane for new Ford V-10

Octane requirements increase as a vehicle ages. This is from burnt fuel deposits on top of the piston and combustion chamber(like spark plug deposits). With a smaller physical volume, and the piston pushing the same amount of air, it raises the compression ratio. Engineers call it "Octane creep". The process starts right away, but starts to be noticeable at about 30-40 thousand miles. That's why they almost never ping when their new. So, if you start with a compression ratio of 8.5, after a couple years it's higher than that and 87 octane fuel just doesn't cut it any more, and you need 89 octane. Add the extra load of an RV plus heat and you get problems. If it gets bad enough, you blow the engine with a broken rod or such. Pre-ignition can be a problem before you ever hear it. I have seen it on an oscilloscope, but that's another story. With aircraft we run 100 octane. No pre-ignition can be tolerated, else a cylinder blows off. My new rig is fine right now with 87, but I'll up it when it asks for it and probably be at 91 at some point. When someone blows an engine at 25-40 thousand, they get blamed for not changing the oil or some other neglect, when it's the fuel that's responsible all along.

Chum lee wrote:
chances are you won't be able to tell the difference between 87 and 91.

Your wallet will know the difference.

Dennis12 wrote:
The manufacturer tells you this because they have tested it. I have a V10. I have run 87 octane and i have run 106 octane from a local airport. Same fuel mileage. See no difference in power or anything else.

What Dennis !! You mean you snuck a tank of 106 low lead in your rig? Watch out the feds don't get you :) (only kidding)

Dennis12 wrote:
The manufacturer tells you this because they have tested it. I have a V10. I have run 87 octane and i have run 106 octane from a local airport. Same fuel mileage. See no difference in power or anything else.

Yes many times this is true, but if performance upgrades are made sometimes a little higher octane works better like in my case..

The manufacturer tells you this because they have tested it. I have a V10. I have run 87 octane and i have run 106 octane from a local airport. Same fuel mileage. See no difference in power or anything else.

dodge guy wrote:
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!

Same here, before 5 Star tuning it ran OK with 87 but after 5 Star is seems to run better with 89, I did contact Mike at 5 Star and said it did ping sometimes with 87 after the 5 Star was installed and he said the factory spark plugs need replaced with hotter spark plugs and this will fix the problem, I still have the factory spark plugs but started using 89 octane and the ping never came back and my motorhome ran better and stronger.

Not sure why this has happen but it did.

Note I do have the full Banks Power Pack system with the 5 Star tune and tow 6500 lbs behind motorhome, so maybe my V-10 just likes the higher octane now..

Running more than the manufacturer states you need to is of no value. There isn't more energy in higher octanes (to the contrary) so your defeating your engines design parameters.
BTW, if it (your very modern eng) pings then there's something wrong.

If I hear my engine pinging, I move up in octane till it's happy. I try and avoid any preignition, or detonation, as it can bend a rod or blow a head gasket. Today's fuel is not what it once was. Some of you will remember the white Chevron 99 Octane pump of decades past.

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

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!