Fuel milage slipping

[gmoney]

Have *2005 LR3 *70,000.
My fuel milage *has been slipping usually get 18 on the road and 14 in town.
Now getting 16 on the road an 13 in town. I am told plugs should not be replace until around 90.0 miles*
Any recommendations

 

[ncburch22]

I have 86k on my '05. Mine has been around 12-13.7 city and about 14.8 highway. Check your air filter and tire pressure. I run my tires at about 40psi which helps a lot being that the weight of the truck is so heavy. I am the second owner of mine so I'm not sure when the last time my plugs have been changed or even if they have been, but I plan on changing them at 90k. Despite what others say, I have found that using 93 octane helps boost the mileage. Maybe not much, but some. One thing you can check is if the exhaust pipe is tightly secured with the catalytic converter. You can do this by turning the steering wheel all the way to the right and look between the frame on the driver side door to see if there is a gap between the pipe. It was a tight fit having to secure the bolts back down all the way, but if you don't want to do it I'm sure you can find a muffler shop that can do it pretty cheap. The backpressure created by the pipes not being secure can cause bad fuel economy.

 

[jimbiram]

I would be sure you get the transmission and diffs serviced with fresh fluids. After having the transmission fluid changed, my transmission was much smoother and I noticed less slipping. Warning, transmission service is expensive regardless of whether at dealer or independent. The transmission filter is built into the pan, and they have to replace the whole pan to change the filter. Mine cost about $900 to get done.

 

[BendRover123]

I had gotten a warning catalyst depleted followed by an increase in fuel consumption from 18MPG standard highway to 13-14MPG. City is 8-9MPG, tire pressure 36psi, running a snorkle, TUFAnT steel rims 18", all services done, engine runs like a chimp, spark plugs new, exhaust is quiet and idels smoothly, cleaned throttle body and MAF.

So long story short at 14MPG your catalytic converter is most likely ineffecicient. Maybe not enough to throw a code yet but getting close.

I bought a maganaflow drop in replacement V8 left right bank and will let you know if it restores fuel economy. Things i tried unsuccessfully:

1. using liquid mechanic to clean catalytic converter, only seemed to work as long as you pour it into your fuel tank,
2. installed downstream oxygen sensor spacer nope didnt work but removed the code,
3. installed spacer with, integrated catalytic converter found on ebay, nope now code is back,
4. cleaned oxygen sensors by soaking them in gasoline, and MAF cleaner, nope didnt work,
5. replaced downstream oxygen sensors, nope didnt help,
6. installed electronic chipped MAF and a chip tuning OBD2 plug thats supposed to provide more power and up to 3MPG better fuel economy, nope didnt work,