Other possibilities:
Volant CAI
Engine break in
Edge EVO
Running Chevron/Shell gas only

I tell you what though, the RP made a bigger difference than those 4 mods above though, I guarantee you!

 

Then don't think about gas mileage.....Doing 70 might get yourself run over, so 75 is almost a must, and gas mileage just isn't going to be over 18....

 

My MPG above is 75-85 on Houston freeways. I get 220-230 miles when the gauge reads half tank.

 

I highly doubt it, but think what ever you want.
You can not claim any MPG gains during engine break in and unconsistant driveing patterns.
I've seen the Volant give no MPG increase.
Edge...who knows...some people claim 3MPGs(which I think is full of Bull ___).
Good quality gas is always a good thing.

I've tried synthetic oils after a engine Break in, on the exact same 100 mile trips I was making with synthetic blend, and there was Zero difference in gas mileage.
Doing 60 with liberal A/C use on Synthetic blend, I'd get 20 MPG every trip.
Doing 60 with liberal A/C use on Full Synthetic, I'd get 20 MPG every trip.

I made this same hwy trip so many times, I know what to expect.
Full Synthetic oil made no difference.

Only reason I used synthetic oil is b/c I wanted to see if there was a difference...there was NOT.

 

whatever dude, later.

 

Interesting thread here as Iam around 17-19 mpg, you know if I keep my foot out the pedal but I changed my muffler and like to hear it, anyways with that alone I saw quicker throttle response and tighter transmission shifts (the stock muffler seemed to be choking which was creating a hesitation between shifts) muffler helped in that, mpg gains dont know probably none! I also replaced the stock in-take tube ( that has air coming from the fender) that thing was UGLY and took up alot of engine bay with it's baffles which muffled the air flow storinging it in these chambers and therefore when it (engine) needs air it takes the stored air in those baffles and you got warm stored air flowing in your engine, when in fact a module in-take tube with a straight flow design alows the engine to get the air it needs, cooler air sucking it from the headlight housing. With an Airaid M.I.T and an AEM dry flow panel drop- in air filter (NO OIL) and with that I did see increase in mpg 1-2 gain. I try to always run chevron 87 octane, once or twice I have used Shell...never circle K or QT type places. I have the FFV 5.4 do you HAVE to ever run E85 fuel ever? It's nice I could run that stuff but am I suppose to, like if you have a 4x4 you have to engage and use once in awhile. Most mods are for looks and sound, any mpg gains are a added plus. I do like that Airaid tube man it looks like should had come stock with it, cleans up the engine bay very nicely, actually looks real good under the hood, not overwhelmed with the stock tube all bulky like.

 

sounds like your figures are a bit high.... no matter what... I have have never been able to get close to 20....

 

I noticed that up till 4500 miles, where I started pushing the engine harder, my fuel mileage was poor. After pushing it hard for just a short period of time the mileage has gone from the dismal 13.5 to 15.5 and now (5000 miles) to 16.5. I'm hoping for further improvement, as the engine is now finally breaking in, but only time will tell.

 

The ONLY way to get better MPG is to install a regular size uncooked egg under the gas pedal and drive in such a way as to not break it. Period.

 

The oil weight will make a difference in MPG. I had the oil changed in our explorer a while back at Jiffy Lube. As we drove it we noticed that she was eating much more gas than usual. When I looked at the oil change receipt....They put in 10w30 instead of 5w20! I don't have any hard numbers. But is was very obvious that the 5.0 in that SUV was not happy on 10w30. There was a small difference in power also. I took it back and they made it right. I watched them put in 5w20 this time. Gas mileage and power went back to normal.

Heavier oils do make an engine work a little harder. Remember that the viscosity (Weight) of an oil is determined by how much pressure it takes to force the oil through a certain size orifice. The heaver the oil...the more force it takes to move it through the system. Period.

Getting a solid 17.5 hwy on a bone stock 5.4 in the truck in my sig line. Went to synthetic....no change. She has just barely passed 1k miles now. So the final numbers may change as she breaks in.

Just got a banks cold air intake system. Should be here early next week. If I don't get better mpg...that's OK. The extra power is always welcome.

I'm not a slow poke. I get on it when getting on a hwy. To be safe you need to be at the speed of the traffic or a little better when merging. I get in the fast lane and do the highest speed I can safely and legally. (Less than 8 MPH over the limit keeps the tickets away around here on the hwy.) If you don't do a bit over the limit you'll block up the traffic flow and be a safety hazard. Been driving for over 30 years. I'm sure I'm well over a million miles. Never been in an accident where I was driving. Ever. (Knock on wood!) God has blessed me.

MPG is a far, far third place behind safety. Slow is not safe on a hwy where folks are doing 80mph. Speed doesn't kill....the difference in speed kills!

YMMV! My .02!

 

I was using 76 gas for a long time, mostly due to it being easy access. My mileage was about 16.9. I started using Costco gas due to cheaper price, after 3 tanks my mileage went down to 14.5. I just put Chevron in and I have already noticed a difference even over the 76 gas. It costs more, but with the difference in mileage its worth it to me.

 

Same here........ I don't put the cheap gas in our vehicles. The wife used to. Not any more though. She's a fast learner! Cheap gas builds carbon deposits and ruins power/mileage over time. Other than the additives...or lack thereof.... I couldn't say exactly why.

 

Keep your tires filled up and slow down. You'd be surprised by how little time slowing down adds to most trips, and how much MPG you gain.

Mike

 

I would slow down....But it can be unsafe. The best MPG is just not worth being a traffic plug and creating an unsafe situation. If the traffic is doing 75-80....and your doing 55-60....your just begging to be involved in an "incident". I don't call them "accidents". An accident can't be helped. It's very rare that a collision happens without somebody doing something stoopid. Slow poking on a major high speed highway is just that....stoopid. Period.

When I pass anything....I get past them as quickly as is safely possible to keep my exposure to them to a minimum. Screw the MPG. I'm gonna get there with my truck in one piece!

I hate it when folks pull up and try to stay even with me. They're creating an unsafe situation. I'd rather floor it and get them way behind me before I steady out the speed again. Screw the MPG!

 

I don't know where you live, but where I live you can have people doing 55 and people doing 80 on the same interstate. If you just stay in the right lane when going slow, and use the lanes to the left if going faster. If you are in the left lanes and other people are going faster, you need to go to the right.

It really is that simple for most areas.

Even if traffic is going 75-80 you can still go 65 safely. I do it all the time.

Mike