Man you gotta have something wrong that car to get 10-11mpg. Or you treat the accelerator like an on/off switch, and think every red light is like the starting grid at Monaco, LeMans, or Silverstone.

Seriously, I drive my six cylinder/5speed SC300 like I stole it. Lots of wide open throttle, an on-ramp is a good place to stretch its legs. 80-85mph on the interstate all the time, and I average about 17-18mpg.

 

I was in same situation when I thought about selling my rare 1997 SC300 factory 5speed which I installed a big turbo. In the end, I sold it to my brother in law. Guess its still in my family, extended that is. Man I loved that sleeper, no one knew how fast it was until it was on boost.

 

The SC300 is quite a bit different than an LS400 IMO. You have a 3.0 V6(which if it is the same as the engine in my dad's 99 Sienna, is fairly efficient too ). Then you have a 5-speed manual and a somewhat lighter vehicle.

My LS has a 4.0 v8, almost 4000 lbs, and a 20 year old automatic transmission. Basically, all of the elements of a fuel efficient car are not there. I was the idiot for not seeing that before buying.

My interstate MPG is not bad though. Driving to Basalt, CO last summer, I averaged 27 mpg doing 80-85 mph.

 

you must really SIT in a lot of traffic, just burning gas going nowhere.
my 2000 GS400 in heavy stop and go atlanta traffic still got about 16.

 

I don't do all that much sitting. But a lot of my driving is nearby, short trips several times throughout the day. I would kill to be able to consolidate my errands and trips into fewer outings, but with my schedule, it is impossible. I'm constantly bouncing between school-workplace-school-home. It's unavoidable.

I don't know if my O2 sensors need changing. Nothing came up when I used my uncle's OBD scanner.

 

Here is the fuelly page for my LS400
http://www.fuelly.com/driver/bjacks12/ls400

I refilled today and aired my tires up to 41 psi. The shop had aired them to 29-30, and this morning one was at 8 psi. I'm going to watch that tire and see if it holds air. I didn't buy the road hazard warranty, oops.

I'm going to lightfoot it like I've never done before and see where the MPGs go from there.