Case Study: 45% above EPA?

[RedDevil]

I'm happy with 45 PSI on my narrow winter tires and found the car handles better on it than with lower pressure. The wider summer tires lost a bit of their rolling quality onder 45 PSI so I may run them slightly lower, but we'll see. The make and quality of the tire is an important factor too; on all my previous cars and bikes FE (and grip, ride quality & tire longevity) went up by changing the OEM tires for top spec.

Although I'm ready to take your word that you can accelerate faster at 45 PSI than at 55 PSI, I wonder what could cause that (other than tire circumference and tire skidding?).
Btw. I think that measuring acceleration is not a very precise way of measuring the effect of tire pressure on FE.
The factor that contributes most to FE while dependant on tire pressure is rolling resistance. The best way to measure that is by coasting down at a set point and speed and measuring the remaining speed at a fixed point further down the road.
Do that repeatedly on the same day with different tire pressure, or do it daily on your commute and build up a big sample to get your data from.
If you can do this at reduced speed then the differing air resistance due to changing weather is less of a factor.

I found getting reliable test data is very hard. I tried to test the effect of lower grill blocking and WAI, but the data is all over the place and it is hard to make a point from them. Do one test and it fits what you want to believe. Do more tests to quantify the gain, and suddenly the opposite happens...
The only strong conclusion from all my testing was that side wind is worse on FE than wind straight ahead. I wasn't looking for that but it kinda forced itself in. From aside.

[101Volts]

Yes, It could take much testing to figure out what works and what doesn't. Perhaps 55 is more efficient for long trips in which there's a lot of coasting and 45 is more efficient for short trips in which there's more accelerating than coasting? *Shrug* Unless I have more data than the few tests and little knowledge I have of the effects of tire pressure on FE, Comparing just a few runs is like walking in the dark.

*Edit, 2013-September-18: Is it like walking in the dark? Edited section ends after asterisk*

I do feel better about running it at 45ish in Moony so perhaps that has something to do with my increased MPG.

The bottom line, I guess, Is to just find what works best for you safely and without putting others in harm's way.

[wobombat]

You're probably right that different pressures are best for different situations/cars. However, I should point out that the difference between 35 PSI and 50 PSI was the world for me. I'd estimate a 5 to 10% increase in FE (1-2MPG) and I refuse to test this because I never want to go back to the lower tire pressure, even just to test. With the old pressure, I would be lucky to get 19 MPG, while with the new MPG I had a tank with maybe 10 hours of almost stopped traffic and I still managed to get 19 MPG.

[101Volts]

That's a good increase. I take it you do a lot of city driving? It may be beneficial to find alternative routes.

Also, If it hasn't been mentioned already make sure to calibrate your ScanGauge quite thoroughly or you may find it's not accurate. Compare the fuel you put in the tank and the miles your car odometer reads to what the ScanGauge says in terms of miles traveled, Gallons used, Etc. The speed it reads may be off at first compared to your speedometer and perhaps the speedometer is off by a bit.

[wobombat]

I'd put my driving at 60% highway 40% city. Somewhere around there.

Thanks for the scanguage input.

[101Volts]

For some reason I didn't mention or forgot to mention that perhaps you could use a GPS to figure out the speed you're going at a given time compared to your Speedometer and ScanGauge.

[UltArc]

Do you have the select shift gear thing? We had a 2006 (I think) LS V8 in, well, 2006, and it had the feature where the auto can move over and select gears. If you have this, it can definitely help.

I test drove a 2013 Buick Regal Turbo Auto and it would only let me go so high in gears- as low as 1k rpms, while my Mustang handle 600rpms and pulls fine- but I choose the gear. FYI, the Regal has 20+ more ft-lbs of torque...

[wobombat]

Good point.
I am now at the 1/2 mark at my fuel guage, and I'm 50 miles over normal. I just might hit 26 on my first tank here.

A few questions from before I still wonder about:

1. How do you DWL if you're already in the bottom of your top gear? You don't downshift to go lower on a hill do you?

2. Is the inability to hold compression in older cars a major factor in preventing good MPG when doing P&G?

3. Do some automatic trannys lock up the torque converter to slow you down in the manual low gears?

thanks to anyone who has insight here.

[wobombat]

Originally Posted by UltArc

Do you have the select shift gear thing? We had a 2006 (I think) LS V8 in, well, 2006, and it had the feature where the auto can move over and select gears. If you have this, it can definitely help.

I test drove a 2013 Buick Regal Turbo Auto and it would only let me go so high in gears- as low as 1k rpms, while my Mustang handle 600rpms and pulls fine- but I choose the gear. FYI, the Regal has 20+ more ft-lbs of torque...

Yes I do have the select shift gear thing (gears 1, 2, 3, and D4). In what way does it help? Do you actually get better MPG from using the manual shift gears?

And I love your taste. I'm rebuilding a 66 mustang right now and I'm a big fan of the mustang marque.

[UltArc]

Originally Posted by wobombat

Yes I do have the select shift gear thing (gears 1, 2, 3, and D4). In what way does it help? Do you actually get better MPG from using the manual shift gears?

And I love your taste. I'm rebuilding a 66 mustang right now and I'm a big fan of the mustang marque.

I respect the love for the Mustang, but to me, it is just my baby. I like certain years, and certain qualities, but I bought my Mustang because it was the best car on the market for me. FR, decent power, 6 speed, fuel efficient. No one makes a better model at the moment, chrysler and hyundai don't understand the sports car market, Datsun is outrageous for what one gets, and the Chevy falls short in several ways, but is still decent. The next Camaro will most likely smash the Mustang. But if it wasn't for good competition, we would be stuck in the monotony of the older models and technology. As in our v6 now having more power than the v8 before, while being even further fuel efficient. The next Camaro engine is looking pretty good, though...

On to the topic at hand, I do not mean moving the gear down to select one, rather while in Drive, pushing it right or left and being able to choose that way.