I have a 2004 3.9l V-6, and I know I should use regular 89 octane gas in my car, that is what Ford suggests, and that is what you guys suggest. However, I heard that I can use all my gas in the tank, then disconnect the battery, and allow my car to sit for awhile. This will allow my computer to reset. Then if I add a higher octane and hook my battery up the computer will automatically adjust my engine for burning the octane which is in it (through something calleda knock sensor). I heard that doing this will increase the power, and the mileage of my car. It sounds too good to be true, and that is why I haven't done it yet. I thought I would ask you guys, and see if any of you have heard of this. In my area the price of higher octane gas is usually about the same as the lower octane gas, sometimes its even cheaper!

 

first off, I have a GT and it says in the handbook that it was made for 87, so I KNOW a v6 doesnt need 89 to run at its best.

secondly, your engine was made a certain way with its cimputer and until you get a programmer(a chip) to reprogram the functions of the engine, a higher octane gas won't do anything. Simply disconnecting the computer and restarting won't enable it to re-calibrate and burn better and that kind of thing.

 

You heard wrong. And whats this about premium fuel being cheaper than regular.

 

yeah, thats nonsense. You might be thinking about diesel. I cant imagine ANYWHERE charging less for a higher octance

 

I'm just going to have to take a picture of the gas station, and post the picture. In my home town the higher octane at the Casey's station is usually 2 or 3 cents cheaper than the regular.

I thought the computer adjusting itself to higher octane sounded too good to be true. I just kept saying to myself; self, why wouldn't they have tuned it for higher octane from the factory if it would preform better that way. I think the reason why my source is confused is because he has a Subaru WRX. He uses higher octane gas in it, however in rural North Dakota he can't always find high enough octane, and often runs on the minimum recommended octane level. The knock sensor automatically adjusts the fuel flow (decreases the amount) to prevent preignition from his high compression. What my friend doesn't understand is that it doesn't work both ways. My car won't simply run richer because it can without causing preignition. Which is where the argument started. Thanks for your opinions on the topic.

Another gas related issue that has been nagging at me is ethanol. What performance (hp and mpg) decrease would be expected from running gas with 10% ethanol compared to straight gas. I know a gas station that has 89 with 10% ethanol for about 5 to 10 cents cheaper than the 87 with no ethanol which I get at my home town. Does it make a difference in anything besides my wallet? I don't mind spending a little more, but is there really a difference?

 

Ok first things first. You said something about your buddy having a wrx and uses premium fuel for more hp...well on his car its true, because 4 cyl engines run a higher compression and on top of that his car is boosted so his car needs premium fuel to run well. And don't mess with anything but gas from the pump for your car.

PS: i cannot beleive that any gas station would charge less for premium fuel. unless they are complete morons..

 

I fully understand that his wrx needs a higher octane for his car to run right. If he uses too low of an octane he will have pre-ignition, because the lower octane will ignite early due to the high compression. It will ignite before his piston is all the way up, and it will basically be pushing through the ignited fuel. This will decrease his performance, fuel economy, and if it happens enough mess up his engine. I also understand that my car doesn't have anywhere near as high of a compression, and therefore doesn't require a higher octane. However, I don't know if running a higher octane hurts my performance. I also don't know what running 10% ethanol in a higher octane does to my performance (although I can't imagine it could help). I can assure you that there are stations in my area that sell gas with a higher octane for a few cents less that regular 87 octane unleaded. If someone out there can help me with the part that I don't already know, I would appreciate it.

PS: I don't know what the gas stations are thinking in my area, but with the amount of money oil companies are making, I would not consider them morons.

 

Ethanol has about 10% LESS energy than an equivalent amount of gasoline.This works out to;10% ethanol=1% less energy overall.Now,about that cheap 93.Here in Wv there are some stations that use natural gasoline or "drip" gas.They buy the drip gas from the natual gas companies,where it's a byproduct,and blend it with oil based gasoline and additives untill it is useable in automobiles.It's usually sold at full service stations at the same or lower price than oil based gas at self serve stations.This could be the reason behind this mystery.One common use for drip gas is in Coleman stoves.It's the stuff you buy in the red cans.