89 Terrible MPG!!!
Senior User
Joined: Apr 2012
Posts: 425
Likes: 1
From: Fort Worth, Texas
Was this in reference to my post? If so how would lower gears help fuel economy at interstate speeds? Alot of time over 70 miles per hour. Now if I can add these with a negligible change to mileage throughtout my travels I would seriously consider it since it would help with pulling my 5th wheel. I travel some accross the state and the speed limit is usually 70 everywhere but when you get out west towards Balmorhea state park at the foot of the Davis mountains the speed limit jumps to 80.
Fleet Mechanic
Joined: Jun 2011
Posts: 1,324
Likes: 3
From: Conway, South Carolina
Was this in reference to my post? If so how would lower gears help fuel economy at interstate speeds? Alot of time over 70 miles per hour. Now if I can add these with a negligible change to mileage throughtout my travels I would seriously consider it since it would help with pulling my 5th wheel. I travel some accross the state and the speed limit is usually 70 everywhere but when you get out west towards Balmorhea state park at the foot of the Davis mountains the speed limit jumps to 80.
Fleet Owner
Joined: Oct 2005
Posts: 20,786
Likes: 1,751
From: Kentucky
Those cracked manifolds are probably the number 1 contributor to poor mileage. The O2 sensor is downstream of those air leaks. They are measuring the amount of oxygen in the exhaust so now the PCM thinks the engine is running lean so it starts dumping in more fuel to compensate.
Your larger tire/odometer error is also throwing off the calculation if you are using the odometer as the measurement of how far you have traveled. If you resolve both of those issues I bet your mileage will increase significantly.
Postmaster
Joined: May 2003
Posts: 3,310
Likes: 9
From: E.Lincoln County, NC
Was this in reference to my post? If so how would lower gears help fuel economy at interstate speeds? A lot of time over 70 miles per hour. Now if I can add these with a negligible change to mileage throughout my travels I would seriously consider it since it would help with pulling my 5th wheel. I travel some across the state and the speed limit is usually 70 everywhere but when you get out west towards Balmorhea state park at the foot of the Davis mountains the speed limit jumps to 80.
but I get bullied all over the highway & people stare and make crude comments...... 
If you could figure the RPM your particular engine gets the optimum MPG's and the speed at which you'd travel most of the time you could gear it and get the best MPG's possible with your truck.
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zogmon
1987 - 1996 F150 & Larger F-Series Trucks
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May 19, 2013 02:22 AM
