I bought my 2001 LS430 with 153k. from a private party January of this year. I was pretty amazed with the MPG on the car. I took it to vegas the first week of taking possession and got over 520 miles HWY driving on a full tank. For the next 2 months I would get about 425-450 city driving on a full tank. I was very impressed with the milage I was getting considering its an 01 and a V8.

Well that didnt last long. Recently this past 2 months I been getting only 325-350 city driving a tank. Not sure what change, my driving habits is the same and I use the same gas station and no check engine lights or anything. Anyone experience a sudden loss in MPG that can chime in?

 

You are probably driving it more aggressive as you are used to the car. Slow down and get better mileage.

 

More youthful driving could account for the drop in MPG, but assuming you didn't go from grandpa to NASCAR driving in style change, perhaps check your spark plugs if they haven't been changed. 160k is pretty high if they've never been changed. They might have just konked out a few of them. Check filters, clean mass air flow (MAF) sensor. Did you recently do timing belts, perhaps the timing was not set correctly.


If you really haven't changed driving habits dramatically, then something is amiss and there shouldn't be that big a dropoff in mpg over such a short period of time.

 

Good advise sir! Im gonna look into doing that over the 3 day weekend

 

Check the vacuum lines for any cracks/splits at the connectors. With the LS400, I would suggest the ECT sensor. That has been one of the big issues with a sudden drop in MPG. At 14 years old, this is a possibility. Neither of these two issues trigger a check engine light in the LS 400's.