Oh I know I am gonna have to have one now. We have a few streets around my home town with 45 mph speed limit and the truck struggles to find a gear to keep, shifting back and forth. That kinda drives me nuts to the point of breaking the law and doing 50 just to keep it in one gear.

 

I have a superchips tune currently running on the 87. My confusion is where does the tune run from. Does it run from the original tune that the engine was currently running at and add changes to that or does it have like a whole new baseline that it starts from? Just trying to figure things out. I have been playing with trying to get better milage since I bought my truck last fall and started with plugs, cap, rotor, then on to a magnaflow cat back duals and a cai. Then replaced the cat with a magnaflow one as I had started to have P300 and P3xx code and could not get over 3500 rpm. The cat fixed that with a major increase in power and response but I still not happy with low gas milage.

 

anytime im driving in a area without going past 60, i always heep overdrive off, makes a huge diffrence .

 

it's been my experience with my truck that the best mileage is running 91 tune with 93 gas.. the 93 tune is way too thirsty, and the 87 tune feels like a dog- it's a good compromise..

 

I could be a little off base here, but:
The transmission shifts with fluid line pressuer so the tuner doesnt adjust that. The tc lockup happens by electronics so yes the tuner bumps that up from 45ish to 52ish. I have the SCT tuner and that feature alone is worth the money! The tuner also removes the torque management crap.
I run the 87 tune with 87 gas. Im about to try the 91 tune with 93 for a few tanks to see how it goes.

Im in the same boat as you with being only able to purchase 87 89 93. Im sure I can find some 91 if I look, but my luck, it will be at a station thats 15 cents higher than the rest......
I felt like a dummy when I filled up with 89 and tried to run the 91 tune and got spark knock. Tooke me a minute to realize that 89 I filled up with wasnt 91. The mentality was "middle tune, middle grade"

 

my truck on 87 tune shift normal in every gear od kicks in around 45.. but with 91-93 its past 50.. and my shift point first to second is anywhere from 5100-5400 and my 2nd to 3rd is 5000-5200 dont havent taken it threw 3rd full throttle 2nd gear seems so long when u see it hit redline over 5k!

 

really... doesnt affect fuel millage?

 

there is an argument that has been going on for a while about gears/mileage..

fact: a truck rolling at 60mph in 3rd gear (with no freewheel such as coasting downhill) is going to tach the same as another truck with same overall gearing doing 60, no matter the mods.. it's not debatable, as the engine has to be turning a certain speed for the gears to be turning a certain rate which translates to speed.

the question is engine load..

if you are maintaining 60mph and are dumping enough fuel in your cylinders to maintain that speed but not so much as to be dumping extra fuel you are going to save fuel..

if you are struggling to maintain that speed you are likely putting the engine under load trying to achieve it- and you put it under load by adding gas, which burns more fuel.. and your economy goes down..

the true way to monitor load is either by vacuum or by a/f ratio.. if you can monitor both simultaneously you can peg the speed that gives you the best economy in whatever conditions- being highway speeds of 60+, around town speeds of <50, or even hauling/towing a load speeds..

all that said- if your tune is dumping either too much or too little fuel into your engine on a baseline, or if you are using the wrong gear, your going to struggle staying in that sweet spot where you can maintain motion with as little load on the engine as possible..

using a lower gear and running a higher RPM where you're NOT dumping excess fuel in the engine trying to keep motion (more fuel than the truck can fire, so it goes to waste) i.e.- lessening load.. is actually better than running lower RPM w/ higher gear that is struggling.

 

Update:
Running the 91 tune with 93 gas. (actually about 1/3rd 87, 2/3rds 93)
I got a little over 1mpg better than 87/87 combo.
Probably could sqeeze a little more out of it with a lighter foot and a full tank of 93.