Hi guys,

I was wondering if my truck would be alright running on 91 Octane it's a 4.0L 207HP, I have noticed a difference in my take off power when useing the higher octane and top end power as well. Basically what are my avantages when useing higher octane? I herd that I will get better gas milage when useing 91...


Please need some help here.

Thanks.

 

You have some misinformaiton there, I'm afraid. Your owner's manual tells you to use 87 octane for very good reasons, and that is what you should use unless you install a Superchip.

The fuel curves must be carefully recalibrated for the level of octane beign used, as it takes significanly longer to get higher octane gas to ignite in the combustion chamber, so it ends up taking longer to complete the burn. Running premium gas on the factory program will not allow for a complete burn of the A/F mixture, best power, driveabilty or mileage, among other things, and should not be done.

To answer your question directly, no, you won't *damage* anything by using premum gas on the factory program, so that isn't a problem you would need to worry about.

You can't get more than about 3-4 more horsepower by doing that, and even that would only be in a best case scenario, you can get about 1.5%-2% more power, and that really isn't enough to actually feel in a heavy SUV like the Explorer. In a 2-ton vehicle with as huge an aero profile as an Explorer, you need at least a 12-15 horsepower gain to actually be able to feel it in the seat of the pants, it's not possible to detect a 3, 4 or 5 HP gain by the seat of the pants, the vehicle is just too heavy. Most people see an actual power drop by doing that (meaning running premium gas on the factory program), again, because the fuel curves are not set up for higher octane fuels, they are calibrated for the quicker burn of 87 octane gasoline.

Basically, it's a waste of money to use premium gas on the factory program in any vehicle that does not *require* the use of premium gas from the factory, *unless* you're running the Superchip, which specifically retunes the engine to take proper advantage of premium gasoline.

All that having been said, it is possible, for example (and this may explain what you seem to be feeling), to have been using what was a lower energy 87 octane gas, then switch to a premium gas with better quality and a higher energy content might seem to feel a little better in that particular engine on the factory program; what you have there is the high-winding SOHC 4.0 V-6, which is a sweet sewing machine of an engine. It winds significantly higher than any other V-6 or V-8 Ford offers in their trucks & SUV's, and has a nice 5-speed automatic transmission as well. However, once again, the maximum power gain you can get is about 2%, and even that happens only sometimes, more often you get just the opposite. Running premium gas on the factory program in these vehicles has been known to cause check engine lights, in addition to less power & worse mileage, which is why the owner's manuals say to use 87 octane.

Simply put, these ECU's do not have the abilty to use higher octane fuels to good or proper advantage unless specfically retuned for the use of premium gas, like happens when you install the Superchip. That being the case, it's basically a waste of money to use premium gas on the factory program, just use the best quality 87 octane available.

You also won't see an automatic increase in fuel mileage from using premium gas on the factory program, usually you get just the opposite, as there isn't enough time to complete the burn of all the A/F mixture. It *is* possible to see a miealge gain in that situation, but that would simply be the result of using a premium gasoline that just happened to also have a higher energy content than the 87 octane gas that was previously being used.

I hope I've managed to make that a little bit clearer than mud.........