Octane has basically NOTHING to do with gas mileage unless you have a programmer to take advantage of the higher octane, even then it creates more power by advancing the timing, but doesn't help mileage all that much. Something you will find though, is that normal 10% ethanol mix with reduce mpg's significantly over 100% gasoline. I get about 1.5 mpg better fuel mileage by running 100% gasoline as opposed to the 10% ethanol mix you find at most gas stations.

It's possible that the higher octane gasoline was a pure gasoline instead of an ethanol mix. Also, as mentioned before, did you account for the wind/temperature conditions, load on the truck, etc? Lot's of variables. I can see getting an extra 50 miles or so on a tank of pure gasoline over the 10% ethanol, but 100 is stretching it a bit.

 

3.55's, about 2100rpm in OD at 70-75mph

i need some bigger than stock tires so I can knock that rpm down some heh

 

since the vehicle can increase timing for E85, I dont see a reason why it couldnt for 93 octane as well. More power = less energy needed to run normally.

 

I believe it is because the E 85 has a tune in the PCM for the E85 whereas a regular truck is tuned for 85. You must have a tune loaded that takes advantage of teh 93 octane. That is what the above post was saying.

 

well, you can mix Gasoline and E85, toss it in the tank and the PCM works with it. what I was suggesting, is the PCM uses knock sensors to adjust spark advance based on detonation (which is based on octane)

just my thoughts, nothing factual

 

My truck (with 33"s) turns right at 1950 rpms, at an "actual" 70mph. I say actual... because I have to correct for my odometer, as I never had my truck reflashed, after going to larger, aftermarket tires.

And BTW, their is nothing that will increase your mileage by 100 miles per tank, short of always traveling downhill, with a BIG tail wind.

Driving on total flat ground, with your cruise control set at 40 or 45 mph, as opposed to 70 mph, might get you close. But how many of you cruise on the freeway at 40 or 45 mph ?

At 65 mph.... or, pulling my light boat at 59 mph, cruise control set, I get right at 18.5 to 19 mpg.

Fish

 

I want to know how you did that and what exactly it does!

if it was out of overdrive then his RPM's would be around 2500 at 70. or atleast thats what mine is at usually

 

I just got the comp re flashed today. ($45). I have not been on the e-way yet to see what the rpms are now. Filled up the tank with 89 instead of 87 and put some cleaner in with the gas. Going to see what kind of mileage this tank gets me.

Yes I am in O/D. If I take it off I am up around 3000. She screams down the road lol.

Thought about doing the plugs too (58,000 miles) I figured that might help a little. Dealership wanted $440! My local shop wanted $300 so I'm not sure if I am going to do it or not.

I have a 1800 mile move towing a u-haul so I am trying to get every mpg I can.

Thanks for the replies and the help as always.

 

wow 440 bucks to change the plugs? Um, yeah thats WAY to much

 

well...

FYI on my trip back, Mother Nature got her revenge... Head wind and this tank averaged 16mpg... so the entire trip average is still 17.5 not horrible... but really more realistic...
Didn't want anyone thinking I had the golden egg...

I'm thinking of re-gearing to 4.10s when I go to 33's... hoping to match stock 3.73 performance