I get ~45mpg with my Ford Fusion hybrid, based on ~15k miles and accurate fuel records. I could probably get a little better if I drove a little more slowly, but on long trips it gets tedious driving slowly. I usually put the cruise control on 65mph on the interstate and live with what I get. I'm very happy with my hybrid after about 18 months of use.

The EPA on my truck is 15/18. I get about 14.5 MPGs with a 3" lift, and larger, more aggressive AT tires. I can still get about 19 on the highway. I guess I can't complain about the mileage I get. I also use 93 octane (available choices in my area are 87/89/93). I don't feel I'm wasting any money with 93. I do notice a difference in power in the lower RPMs, and it does seem to last slightly longer than 87.

EDIT: I was also under the impression that forced-induction vehicles need 91+ octane fuel.

Had one of those monster 4x4 4-door pickups. Mileage was horrible, and that was when I drove 30K miles per year. I bought a Focus and it obviously got better mileage. For a while I was still driving lots of highway miles. Around here it's 65 MPH limit but many drive 75-80+. After a while I decided to "try" staying solely at 65, which is difficult, you get run off the road by everyone. But I managed and did notice that I got an average of another day of travel out of every tank of gas. So with about 12 gallons and driving 50-60 miles per day it seems I gained about 4-5 mpg just not speeding along at 80. And the car was obviously much happier because the RPM was like 2-2.5 grand versus nearer to 3 grand or higher.

Speed limit on major highways in Texas is 75 m.p.h.

I only go 60 - 65 to be a "better steward of gas."

I do not care if others honk at me as I stay in the right lane.

I lived in Germany and saw the results of excessive speeds.

When cars on the Autobahn got in wrecks, the engines left their cars.

On a trip of 200-300 miles, driving 65 vs 75 means you will arrive a few minutes later, certainly less than half an hour difference, and the difference in gas mileage is significant. By slowing down a little, and running the tire pressure near the maximum recommended by the tire manufacturer, not the car manufacturer, I gain a significant amount of gas mileage. The ride is a little rougher with the higher tire pressure, but not really noticeable. I do get passed by a lot of traffic, but I've long ceased to worry about it.

You are right.

I would not risk my life for a few extra miles. I keep the tire pressure at exactly the right pressure. As for speed, I go 5 above the limit usually, 10 above if I'm in a rush. I only go the limit when cops are around or if it is raining hard. I don't usually go above 80 mph, because things start vibrating too much.

I don't believe I'm risking my life. The tire manufacturer is required to put the max inflation pressure on the tire, and that pressure is conservative. The car manufacturer is concerned mainly with ride quality, and always recommends a pressure significantly lower than the max pressure the tire maker provides. Lower pressure actually causes increased flexing of the tire, which I feel is more dangerous than running a higher pressure. I don't go all the way to the max pressure on the tire, but I do go close. If the tire is printed with 50psi, I run ~45 or so, and the car maker usually will recommend ~32psi, which is, IMO, too low.

I usually add 1 or 2 psi to the recommended value, but I would not run it high just to save gas. It is true that running with underinflated tires is more dangerous in most cases because of the risk of blowout. However, overinflated tires reduce friction and can be a problem when it rains.

For tires, the height of the side wall is important too, for more than just ride comfort. If the side wall is too short, like in some sports tires or "pimped" tires, not only is the ride uncomfortable, but you can experience sudden loss of traction during cornering, especially if your suspension is also hard, and ride height low. The tire wall height is actually part of the suspension, and when the suspension bottoms out, you can lose traction. This has actually happened to me with such a configuration (hard suspension + low ride height + short tire wall), and this has resulted in a crash.

Usually the recommended PSI listed on the vehicle is due to the weight of the vehicle and the size of the tire that comes equipped with that vehicle. Low profile tires will require higher PSI to hold the weight of the vehicle compared to a tire with larger sidewalls/smaller rims (more volume). A heavier vehicle with the same exact tires as a lighter vehicle should also have a higher PSI to due to the extra weight.

If you add/subtract significant weight to/from the vehicle, or change the tire size originally equipped, you will need to adjust your air pressure accordingly.

There is also a difference in PSI between (P)passenger tires and (LT)light truck tires.

I added a bottle of octane booster to tank of regular gas. ($6 to treat 18 gallons)

Mileage went from 19 -> 21 m.p.g.

I filled car with 89 octane gas to see if I maintain the 21 m.p.g.

If so, it would be cheaper than using an octane booster.

You're basing this on one tank? Haven't you said something about being a scientist/chemist? What "boost" did that $6 bottle give those 18 gallons? Meaning "to what octane level" did it bring the gas you treated with it? There are a lot of factors to consider, such as the type of driving you did, the temperature, tire conditions, etc.

Honestly I'm all for fun experimentation, but to find something sustainable I'd rather just drive slower, smoother, and make sure my car was mechanically maintained properly as well as properly tuned up. And, sorry I've said before that if I were not totally happy about getting 20'ish for fuel economy, then I'd buy a different car where I expected to get 30+ or higher out of it.

I use Torque for Android. It displays almost any info OBDII can output. One of the gauges I use is "Instant MPGs". It show's you in the moment your gas mileage as you drive. With that info, I can adjust how much pressure I apply to the gas pedal to get a sweet spot of MPGs and acceleration.

https://www.tacomaworld.com/media/on...l?d=1431459784

That's a GREAT idea! +5 Yes, you can buy an ODBII device and I think what replica9000 is doing is way better than old school guesswork. This way you'd have direct information as to what the engine is doing all the time.

You can also use Fuelly to track your gas mileage.