dlstewart01

Air flow and fuel mileage testing by Oak Ridge labs for the government.

This is not what people want to hear but it is what it is.

There is a great deal of info in the link...it is a long read but interesting...

http://www.fueleconomy.gov/feg/pdfs/...02_26_2009.pdf

A summery and conclusion of the tests...

Results show that clogging the air filter has no significant effect on the fuel economy of the newer vehicles (all fuel injected with closed-loop control and one equipped with MDS). The engine control systems were able to maintain the desired AFR regardless of intake restrictions, and therefore fuel consumption was not increased. The carbureted engine did show a decrease in fuel economy with increasing restriction. However, the level of restriction required to cause a substantial (10–15%) decrease in fuel economy (such as that cited in the literature3,4) was so severe that the vehicle was almost undrivable. Acceleration performance on all vehicles was improved with a clean air filter.
Once it was determined how severe the restriction had to be to affect the carbureted vehicle fuel economy, the 2007 Buick Lucerne was retested in a similar manner. We were not able to achieve the level of restriction that was achieved with the 1972 Pontiac with the Lucerne. The Lucerne’s air filter box would not hold the filter in place under such severe conditions. (It is believed that this testing exceeded the design limits of the air box.) Tests were conducted at a lower restriction level (although still considerably more severe than the initial clogged filter testing), allowing the air filter to stay seated in the air box, and no significant change was observed in the Lucerne’s fuel economy or the AFR over the HFET cycle.
Closed-loop control in modern fuel injected vehicle applications is sophisticated enough to keep a clogged air filter from affecting the vehicle fuel economy. However for older, open-loop, carbureted vehicles, a clogged air filter can affect the fuel economy. For the vehicle tested, the fuel economy with a new air filter improved as much as 14% over that with a severely clogged filter (in which the filter was so clogged that drivability was impacted). Under a more typical state of clog, the improvement with a new filter ranged from 2 to 6%.
4.2 FUTURE WORK
Power in the modern SI engine is controlled by manipulating the manifold pressure through throttling of the intake air. The increased restriction of a clogged filter affects ultimate power but not fuel economy of modern SI engines. Any additional pumping loss due to the state of the air filter is offset by the throttle. Conventional diesel engines operate without throttles—although throttles are in use in some diesels today for active control of exhaust temperature and species, to enhance warm-up, or control exhaust gas recirculation, these throttles are full open most of the time. Because the diesel engine is unthrottled, and airflow is high even at light load, the added restriction from a clogged filter may have a measureable effect on fuel economy. Future work will investigate the effect of intake air filter state on a number of diesel vehicles.

Bow-Tie-Beast

I agree, I average 13, but I think he should be running at least 60psi in those 33x12.5x16s, if not 70psi in the rear.

GoldenOne

The air filter is like new, stock bumpers, ex cab, not sure which gears my truck came with. My truck starts to ride like *** with my pressures up much more than 40psi.

Bow-Tie-Beast

Does 1BadZ95=GoldenOne?
If your truck rides like *** with the pressures at the proper psi, then I would look to replace the shocks on it.
If you want more mpg, you going to have to have more than 40 psi in your tires unless your running 22" rims or bigger.
You can also have your tires balanced too. If there weight is off some, it will throw off your mpg. You will also hear a wobble while driving and brakeing.