Ok so after reading all 5 pages I have an idea of what it could be but im gonna ask anyhow.

I 0have a 01 1500 5.2 magnum. Before I gave it a tune up (oil, wires, plugs, and filter) and added new back tires 265/75/16 (supposed to have 245/75/16 wanted a taller tire to fill fender wells out back)I was getting 310 to a tank. I noticed today that I am at 245 with less than a 1/4 left. I figure 265-285 now will know in 2 days. I was at 198 when I hit a half a tank. 75.00 to fill it full at 3.18 a gallon. I had an evap issue last month and spent $75.00 on a frakin filter/diagnostic to fix that issue.

I don't drive like an old lady and I don't dog it like a kid would either.

Now the question is why is it getting worse and doing it after the tune up?


CTPAFW163 How hard was it to adapt the air cleaner to your rig? Any changes in performance?

 

A 2001 has a deathflash , when I removed it it was a totally diffrent truck . It's like someone took a 5k ancor off the end of my truck

 

You have bigger tires.

Any bigger tires will demolish your everything with the puny 3.55 gears

 

A 265 tire isn't significantly larger than a 245. And measuring mleage by 1/2 tank or any gauge is not even close to accurate (lucky to be within 15%-20%). Measuring actual miles and gallons is the only way to be even close.

And death flash would possibly impact it, but should not be any different form before changing tires.

 

Just like everybody else on here I want better mileage, even 1 mpg is better than nothing. I'm hoping to achieve this by doing my plenum with hughes, changing my spark plugs (haven't been done in awhile, wires, rotor and cap have been done within the past few years) cleaning the IAC, slapping on a new MAP and changing the front O2. Does that sound ridiculous? When I got my truck 8 years ago, it was getting so close to 15mpg, now its down to 11-12.5ish...maybe it's just getting tired with 144xxx... So for me, thats bad considering what it was getting.

 

Skip the MAP sensor, go for the pre-cat O2 sensor. Also deal with the cat....

 

Just did a 500 mile round trip run this past weekend and got 15.18 mpg on the highway.. No a/c and cruise set at 74...not too bad i suppose..i average 11.5-13 in the city since i replaced the motor back in march...

 

You kinda mis understood me I am measuring by a full tank so full it spit up. I mentioned the half tank to let you know that it drops faster than running on a fuller tank, why I do not know it just does. Right now I am at 262.5 and have a 1/8th of a tank left.

An what is a death flash? An how do I remove it?

 

8 years ago we didn't have 10% performance robbing ethanol in the fuel. Around town I get 8.5 winter/9.5 summer, Hwy about 14.5 winter/ 15.5 summer.

 

Death flash was dodges answer to an engine that didn't have a knock sensor, and exhibited lots of spark knock.... so, they reprogrammed the PCM to pull timing. (thus, eliminating spark knock, but, also robbing power.)

To get rid of it, get a tuner from Hemifever Tuning. (he is a member here too...) 265 for three canned tunes, 365 for custom. Canned tunes will be fine for a stock truck, with just bolt on mods.