I run 87 with a superchips tune that recommends 91 (tow), I have no knocking. Runs like a champ.

 

I run 87 in my truck, I did have the fun of runing 91 once, as the gas station ran out of 87 and gave me 91 at the same price. My work van says it should use E-85, But we dont have it lol so it get regular 87, Last time I filled it up was the first time, it MIGHT have had 10% Ethanol. My trucks never had any ethanol in it, since we dont have any stations selling it in my Province.

 

ah the good ol' days. Knocking like mad and running like a champ to the nearest bush. Then watch and try not to laugh... made even funner with a flaming poo in a bag.

 

If you run anything lower in octane than what is recommended, modern anti-knock sensors will correct timing (ignition and valve if available) to reduce the knocking (pre-ignition). This will cause a decrease in power and, therefore, poorer mileage.

However, the 85 in e-85 is not the octane rating, it is the maximum percent of ethanol in the fuel. From Wiki - "In a liter-to-liter comparison, E85 has 33% less energy content than "pure" gasoline (and 30% less than the E10 gasohol blend that is sold by almost all retailers in the US). Depending on the vehicle, this can result in a notable reduction in fuel economy and means that while E85 is cheaper than gasoline per gallon, per mile it may be more expensive. Additionally, due the chemical differences between E85 and gasoline, fuel systems and engines not designed or modified to use E85 suffer increased wear and may fail prematurely"

Even though I rarely trust wiki without cross checking, this looks pretty accurate.

 

I track every tank of gas and it's mileage on paper. With the 87 octane and the superchips 87 octane (and tow) tune I get 17 mpg average. With the superchips 93 octane gas and tune I get 18 mpg average. So I figure the extra money you spend on premium gas you get one free gallon of gas so it pays for itself. Sticking with the 93 tune cause it makes the truck run so much faster and the added 1 mpg.

Never tried the economy tune and don't intend to.

 

Wtf? Lost me...

 

I was kinda trying to lol. dont ask haha

 

Ohhhh...nevermind....haha...I almost forgot about that...

 

Nicky Nicky Nine Doors.

 

But you are running a "modified" engine system. A TUNE is a modification. It plays with the engine management paramaters to optimize whatever you are dumping into the engine.