Hi
My ls400 1999 is doing 16 mpg on highway
I changed the oil,air filter and the spark plugs
Not helping

Any ideas ?



 

Is this just recently? May want to check the O2 sensors.

 

May want to check for vacumme leaks. I had one that actually helped my MPG, but you never know. Check that you don't have a sticky brake.

Was that a hand calculation or the computers number?

 

heard changing out the fuel filters help as well. problem is we have two. one in the fuel line and one in the gas tank area.

 

I'm averaging 23 mpg. Mostly highway. Supreme fuel.
Hope you find your mileage thief.

 

guys stay on topic in terms of what the OP could do to better his mileage, we already have a couple dedicated gas mileage threads .

OP-how do you drive? if you are driving at high rate of speed in hot weather with the AC on, consistently, then that's the mileage you're going to get.

 

is the OP even a person, that sn looks awfully vague and computer generated. from the united arab emerates?! but heck i could be wrong.

to answer the ? i get a mixture of 20-22mpg mostly highway on the weekends only. i drive 5 miles to work weekdays on a bone stock car. my rpm hardly ever goes past 2k rpms and the ECT is on NORM. i would check your driving habits.

 

im in the same position as the OP. car's mpg is shietty for a 99 ls400 with vvti. might have a vacuum leak from the brake booster cus the brakes gradually get stiffer when the car is off, does this affect MPG in anyway? lol

 

i believe you only need to do the one on the fuel line, but i also heard we dont needa change it on our cars, lexus cars.

 

is the parking brake released?

 

uh huh it is, and when im driving i can hear my tranmission from inside the cabin! its loud when i start my car from a cold start as well ..of course it gets louder the faster i am... idk whats going on, my fluid looks good. pink

 

Do u have CEL on or something?
Vaccum leaks/Sensors error readings will trigger CEL

 

Its 12 years old, could be that the engine temp sensor is starting to go, making your car run rich as it always thinks the engine is cold.

Do you get white vapor from the tailpipes? Fuel smell?

 

I get fuel smell but not sure about white vapor, it's been cold lately. And my temp gauge works fine, but the car does take a while to warm up. If I let it warm up and drive for a mile. Itll be cold again After 6hrs of not driving and I would need to warm it up again.

 

I don't have any CEL lights on man, but my car seems to stay idle at about 1.5k and won't go down even after like 5 mins of warming up, so do you guys it's the temp sensor or something?