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Improving fuel mileage on my FL Classic

My name is Jonathan Gilles, my wife and I just leased out first truck, it's a 2007 freightliner classic xl with a Detroit 60 series under the hood. What can we start looking to install on this truck to bring up or mpg, we've had an imframe done and the mileage is currently 883230. hopefully there's a list or something of the sort you could point us to. The current mpg is about 5.9 in the last 2 Weeks. Please help if you can thanks.

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Here is my plan of attack of stuff that I have used and know works.

First head to a Detroit garage and have the charge air cooler tested, and make sure you don't have any other mechanical problems that hurt fuel mileage. Since you just had an in frame I am guessing your ok if it was done right. Then you can start modifying things.

Slow down. Depending on which gear ratio you have: 3.70 run 57, 3.55 run 62.

Pittsburgh power flow through muffler or Walker Mega flow muffler

Fleet air filters

OPS and switch to synthetic (the synthetic oil helps with fuel mileage)


FASS fuel system

Low rolling resistance tires, also make sure they are centered and balanced. Align the truck also if you are experiencing wear on your current tires

De EGR the engine. Then you can add Pittsburgh powers manifold and turbo and have them program your ECM

Now if you want to start really modifying the truck you can change the exhaust system to take the mufflers off the front of the truck and make either a weed burner if you don't idle or put the mufflers up the back behind the truck. This will reduce wind drag.

You can also take the dual air cleaners off the outside and get an under hood filter. This will reduce wind drag.

I have not tried this yet but I believe they work, there are several people here that have done this.

Micro blue bearings, tranny, and rear ends

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This question comes up on kevins show often. (Sirius 106 12pm est weekends 4pm). Keep tuned in and you'll get up to speed on improving mpg.

His list of "no brainers" , low cost with quick return on investment inclued a Fleet air filter(s) and a pitsburg power muffler. Also have the charge air cooler tested for leaks.

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Just a thought: I would stay away from using synthetic oil in your motor because it has a detergent additive in it that can "char" when under extreme heat temps. I would, however, use it in the Tranny and rearends.

Update (11/08/2015)

I strongly urge you to NOT drive with the cruise control on unless you are on perfectly flat ground as the computer will often overcompensate for small inclines in grade shooting your boost pressure up which in turn uses more fuel than necessary. With that being said, drive using your boost/manifold pressure gauge. When driving correctly, you should see your gauge at 25psi or lower on average unless pulling steep grades. The lower you are able to keep it, the less fuel you are burning which in turn should increase your mpg averages.

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