Are you using premium fuel? My commute consists of 15 miles of suburban, slightly rural and I get 21-22 on those tanks, high 20s on road trips (flat terrain, 75-80 mpg).

 

I have tried premium, mid-range, and regular, and it seems to make no difference at all in my gas mileage. All three have the same amount of energy per gallon of fuel. It might only make a difference if the engine uses its antiknock sensor to change how it uses the fuel.

 

YES I always use 91 Octane from either Chevron or Mobil.

My tire pressures readings are 34 in the fronts and 36 in the rears.

I haven't really pushed my car hard yet, since is new.

I find it surprising that the advertised MPG is higher than my previous 2008 GS350 with better emission and a 8 speed transmission. So I expect this car getting better MPG, yet to find out is a gas guzzler. Which make me think I should of gotten a LS460 instead.

Today I hit 600 miles since I purchased back in June 13th. Still getting 16.5 mpg average.

 

Pretty much my thoughts (except I didn't want an LS).

I mean, I can afford the fuel bill without an issue. I was just sort of surprised and disappointed with my real world mileage. On top of that, this car has a tiny gas tank!!

 

I have a '15 GS 350 F-Sport RWD and i'm averaging 15.9 according to the dash...But this is with "spirited" driving in mostly S+ mode...ive been getting slightly better mileage in norm mode with less-spirited driving.

I have about 1100 miles on her now and i've noticed the mileage creeping up slowly.

...and I too was shocked at how small the gas tank was. . .

 

Lots of answers without even knowing what type of driving he does. My wife was getting in the 18s in mainly surface streets locally. Her mix now has a lot of traffic lights but with several stretches of cruising at 60mph and she is getting in the 21s.

I drove it for a week commuting into near downtown Houston from the suburbs with a mix of open freeway, some stop and go on the freeway and a handful of traffic lights and averaged 26 for the week. In pure freeway cruising at 75 mph or so it gets 30-31. Btw, those figures are basically identical to the 2010 we had that was my car. Apparently the eight speed doesn't do much for mileage.

BTW, I don't believe in the break in theory either.

 

Sick u can convert ur trunk into an extra gas tank and just run a canal to ur original one. Then u'll have like 100 gallons gas tank.

 

But the LS460 might get even worse mpg with its extra weight and V8...

When my GS350 RWD F-sports (2013 & 2015) were new, they both got horrible mpg (16ish) for the first couple thousand miles. That was with mostly easy driving. Now it's more at 18-20 mpg, but I have lead feet, always drive in Sport S+, and 70% city. It's possible to get in the 20's, but just give it some time and you'll get it up there.

 

Good idea!!! But my trunk is full of strollers and gym clothes

I'm curious to see what my gas mileage will do after my first oil change.

 

Indeed, I've only run premium.

There's no way around the fact that this is a rather heavy car... every time you have to motor up from a stop you're going to be burning a good deal of fuel. The more frequently you hit red lights or stop signs, the worse your mileage will be.

Switching to a heavily car will only produce worse results... even with a 4-banger, you're going to be guzzling to get moving... our existing 6 is very efficient with light loads as seen cruising on the highway; poor city mileage is a function of its weight.

 

I thought most people would be replying there was something wrong if you were avg. 16.3 mpg in a 4th Gen, I did not know the 4th gen got such poor fuel economy with a DI V6 and 8 speed auto and using 0W20 synthetic, it gets roughly what my V8 5 speed GS430 using 5W 30 synthetic gets, I avg 16-17 stop and go and have got 29-30 highway on long trips before. A F sport is on my list of next cars, the fuel economy is not a deal breaker but it is a little disappointing they can't get better fuel economy out of a DI V6 with a 8 speed auto. I thought they tuned the 4th Gen to get better fuel economy over the 3rd Gen because the 3rd Gen GS350 achieved better 0-60 times.

Just a few things to maybe help FE.

-Keep your tires a little overinflated.
-Try coasting when you can, coast more to stoplights to avoid coming to a complete stop when you can.
-Keep windows up on highway, keep AC off when you can.
-Take out extra weight if you can.
-Use cruise control when you can
-Use top quality synthetic oil.
-Make sure air filter is clean.
-Try to make less trips and accomplish more things which helps eliminate short trips, car not running at optimal temp.

 

I just had my oil change and no difference. I was expecting to get 40-50 MPG after but that didn't happen.

 

Damn for real man?? I was hoping for like 60-70 mpg!! lol I have been driving a company vehicle and not putting the miles on my GS, so I'm at like 9,700 miles... Almost there!!!

 

I don't believe for a minute that Lexus could not get better mileage if they wanted to!

The vehicle is just over 200 lbs heavier than my 10 year old Acura TL which gets about 35% better gas mileage (combined)! I could drive the highway 730km with my TL, I can't even get 500km with the Lexus (same size tank).
Alas it's a Luxury car so increasing mileage doesn't seem to be on Lexus's radar. But hey we all bought them knowing they aren't the best when it comes to mileage
But I really do wish they would put a bigger tank in !

 

Mileage not great and not better than my previously owned Genesis 4.6 V8. Loop driving about 21 mpg and on long run as much as 26.7 mpg