03 w/no mods that I know of very low economy

[RWinzen]

I'm new to this, so forgive me if I'm not using the correct stucture. We currently have two '03 6 speeds and one '04 auto. One of the '03s is getting extremely poor economy. The only changes are a K&N and Silverline exhaust, nothing to the engine that I know of. I have modified my '04 and from that point, I did I noticed how far off the overhead's mpg came be. So I'm not basing anything on that mpg reading, all is calculated at the pump. There is one consistant factor from the overhead, and that is ODO & DTE. When I fill up one of the '03s and the '04 and clear all the setting on the overhead my DTE will read anywhere from 500-550. The other '03 (191k, LWB) only reads 340-375. The bad part is, that is all the miles I can squeeze out of it. It consistantly gets 12-12. 5 mpg and that's it. Before I modified the '04(116K, LWB), my overhead was close, now it reads about 4mpg higher than actual. The '03 in question reads about 4-5 higher that actual. The 2nd '03(SWB, 152k) has not been modified that I know of and the overhead is within 1. 5mpg. Something makes me think the LWB '03 has been modified by the previous owner. I checked the gears against the VIN and it 'came' with 3. 73s, but I know the gears could have been changed. I'm at a loss and before I sink too much in to it, I'd like to know some other opinions. I unfortunately have to get out to customers, so I will login and check this later.



Thanks,



Ron

 

[betterthanstock]

First, at 191K, have you lashed the valves?

An open valve will dump out compression.



The other test is, with engine idling, both hot, and cold, open the oil fill cap and feel the blowby gases. That tells you the condition of the pistons/rings.

 

[04 Diesel Power]

First, at 191K, have you lashed the valves?

An open valve will dump out compression.



The other test is, with engine idling, both hot, and cold, open the oil fill cap and feel the blowby gases. That tells you the condition of the pistons/rings.

What do you look for?

 

[RWinzen]

I plan on doing the valve Saturday. I'll check the blowby also. Thanks.

 

[RWinzen]

My '04 gets 16-17 without towing, 12-13 towing. The other '03 is in the 16s. Haven't used it to tow yet.

 

[AMcCormick]

Wow my overhead varies alot but will settle down and read 24-26mpg at 65mph depending on how patient I am at the pump DTE over 600 miles. I've found since I dont have any fuel vent mods that if I fuel slowly I can get lots more fuel in the tank as opposed to letting the pump just shut of on overfill. I havent hand calculated anything so just take it has it is. Driving down the Keys earlier today looked up and it read 38mpg. How killer would that be if it was real. Hit reset and came back to 27 at 50mph.