A few years ago, I posted about my attempt to get the most highway MPG in an experiment. I did another experiment yesterday with a great result.

I recently had my spark plugs changed as my car passed the 60,000 mile mark and that is required maintenance. On Weds I drove the Pa Turnpike from Pittsburgh to Philly. I thought I reset my car computer before departing. I generally do not futz with it so it has been many miles since being reset. Anyway, when I arrived in Philly, it said I was getting 17.3 MPG. I was shocked and figured that they new plugs were somehow installed wrong or misgapped or something of that nature. But 17 is about my normal city (Pittsburgh, hills, winter, AWD car) MPG. So I started wondering if maybe I didn't reset the computer after all. So I made sure it was reset and on the way home I drove for 1 hour on the Turnpike from Philly to about the Harrisburg area at 60 MPG with no jerky accelerations/.decelerations. ( I would have gone 55 but I was almost creating a traffic jam at 60.).
The weather was perfect...no need for A/C or heat and the windows were closed. As close to perfect conditions as I could get. Bottom line is that over that perfect 100 mile drive, my AWD LS460 got just under 32MPG on 89 octane gas, according to the computer. Yeah, I know, the computer might be optimistic and real world driving (higher speeds, more stops and starts, hills etc) is much tougher on MPG. The last time I did this I got 29.8 MPG. So the bottom line is that the plugs were put in right and the car is a champ. And I can brag that I got 32MPG on my AWD flagship Lexus LS460 w AWD!

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Driving on the Turnpike for 1 hour in perfect weather at 60 mph and no AC should increase mpg. 32 mpg is great and for a vehicle its size the 460 mpg isn't bad during highway driving. I'm approaching the 60K mark and my spark plugs isn't required to be changed according to my maintenance book and my 460 isn't AWD.

 

dlbucks10, what year LS do you have? I wonder what years require a 60K spark plug change and what years do not. I had an independent (who I've used for a long time and fully trust) do the work. The plugs were about $150 and the labor was (only, to my surprise) $150. About $300 for all. Not a big deal really. I'm sure it would have been double (or more) at the dealer. Also, I get your point that my conditions were perfect for MPG but for an AWD flagship that's rated at 23 highway MPG using 91 octane...to get 32 MPG on 89 is more than just "not bad".

 

my 07GS350 RWD only gets 11mpg in the city. WTF?

 

Something wrong with your GS..definitely

 

I routinely get 25 - 27 mpg's every week. And I drive 500-600 miles per week. I'd say 400 of those miles is highway, but I'm stuck in traffic sometimes on that highway.

I've been very impressed with the fuel economy of this car - then again I'm not driving it anywhere near as fun as I should

 

Im still getting just 11-14 mpg in my 2007 RWD GS350. Could this be normal for only driving in stop n go traffic. Always with the AC on. I like to leadfoot it around LA.

 

11 to 14?!?..two things come to mind. Lead foot with bonus cement shoes and possible bad plugs or something

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I get 21-22 mpg mix 40% city / 60% hwy driving.
I got 27 -28 mpg on my recent LA to Las Vegas trip going 75 - 80 mph. Not bad for a large car.
I think it can go over 30 mpg if I just cruise at 70 mph.

 

My 600hL normally gets 22-23 mpg indicated in mixed driving during the summer months. In the coldest part of winter, I'm getting closer to 19-20 mpg indicated due to the reduced battery efficiency. When I went on a summer road trip across Iowa (steady 75 mph), I got 26 mpg. I'm heading out on a 600 mile trip to the Colorado ski resorts this weekend and am interested to see how I do (cruise will be set at 80 for this trip, with a 75 mph speed limit across Nebraska).

Note that the mpg indicated on my 600hL is consistently 1.5 mpg higher than what I actually get when I calculate my fuel economy manually.

 

That is exactly my experience.

My indicated mpg is the opposite. It regularly reads about 1 mpg LOWER than actual.

I wonder what other owners experience.

 

Mine reads 1.25 to 1.5 mpg higher than actual.

 

I looked today after a refill. It showed 18.1. All my driving is city and some general xway around the city. I'm very pleased.