This is a bit long winded but I feel like babbling while my post doesn't really go anywhere.
I like, and have tweeked my PSI up to the point (over the listed PSI in the door jamb) to where I don't notice any ride difference over expansion joints/pot holes. This is only a few PSI at best for me and my applications. IDK if this actually helps MPG as I have never noticed any improvements by doing so.
I have gotten and continue to get better MPG by using the cruise control often and by driving conservatively.
I would love to get better MPG in all of our vehicles but, not at the expense of day-to-day comfort. I want an increase in fuel economy of more than .05 MPG if I am going to feel more of the road imperfections. I'd like something along the lines of 2-5 MPG and I don't think it's obtainable.
I think that driving more conservatively has more to do with MPG than tire PSI. I have also never noticed any improvements in MPG by using Synthetic Oil either. Again, just babbling!
I have been measuring MPG over the last 35-40 years on every tank of fuel in every vehicle that I have owned. Oh sure, I have missed a measurement here and there! But, what I notice most in getting better MPG is...consistant/warmer outside tempuratures, conservative driving habits, the proper octane fuel, proper tune of the engine(mainly 02 & A/F sensors) and good care of the vehicle itself including the tires.
I have never noticed any better MPG by keeping or not keeping the vehicle waxed or removing the roof rack cross beams on a vehicle so equiped. It is what it is!
I strongly beleive that one needs to do many things in order to increase MPG by a noticable margin such as...Syn lubes everywhere(engine, tranny, diff. etc.), proper or increased PSI in the tires, decreased weight in the vehicle including the trunk/hatchback along with mild driving habits. And this only nets a few MPG at best compared to not doing these things. Doing one thing all by itself doesn't show consistant MPG increases. You might get a "Flyer" now and again...a large MPG increase for no appearant reason.
Warmer outside temps has more to do with better MPG all by itself than any other single/multiple thing(s) that I have ever done in all of my years of measuring fuel economy. Plus, buying and driving better MPG vehicles.
Years ago, my wife an I used to drive on long 2/3 week vacations in our 4 cyl cars along with our frinds in their V6 vehicles(aprox same wgt cars), 4 cyl ACCORD/V6 CLEBRITY or 4 cyl Camry/V6 GrandAm in these examples. We would drive anywhere between NY and Myrtle Beach and FL.
Our friends V6's EPA rating were very close to our 4cyl engines up to a certain point. But when they would get into the throttle and bring up the speed on the highway(as to make up better time travel), their MPG would drop about 8-10 MPG and ours would only drop about 2 MPG if at all, while traveling at the same highway speeds as one another. But as long as they were driving easy in their V6, the MPG was close(although still a bit lower than our 4cyl).
Driving at 55 MPH, the 4cyl(38+MPG) and V6(32+MPG).
Driving at 65 MPH, the 4cyl(36-37MPG)& V6(25-27MPG).
Driving at 75 MPH, the 4cyl(34-35MPG)& V6(22-23MPG).
That's between 14% loss for the 4cyl and 40% loss V6!
This isn't the only example I have...There are more! What we notice is that while driving conservatively, both 4 and V6 are close in MPG but, don't get into the excelerator too much in the V6 vehicle as the MPG really drops like a rock as where the 4 banger does, but not as much.
Just babbling! No sarcasm please!
Yeah right! I can hear the comments already