haha... you are not starting in.6th gear by setting to 6. The transmission auto down.shifts once you come to stop. Its not a true manual. In full auto, were you not feeling it went to 6th?

 

I think my car gets usual mpg compared to other ls430 on here. 05 100k miles. 18-19 city and solid 25-26 highway. I dont know if I should be doing this but I mix half mid and half premium to get 91 octane. I am planning to change plugs this week and clean throttle body along with the maf. Probably throw in a bottle of techron concentrate. I will see if there is any change. Hopefully mpg goes up not down LOL

 

I don't believe we purchased this kind of automobile to get terrific mileage.
We looked at small cars that get good mileage and they were cheaply made and didn't ride very well.
Then we decided since we don't drive many miles per year, we are retired, we would look at luxury autos with all the "bells and whistles". The Lexus filled the bill and we love it.

 

In fairness, you don't pay over $10 a gallon

 

Interesting, and embarrassing I didn't know that.

I think it shifted to lower gears a bit too often. It'll be interesting to see if this method makes a difference on the motorway, as that's where the poor mpg really bites, especially long journeys across Europe.

 

My best recorded average was 27MPG and that was straight 4 hour road trip highway driving. As soon as I got back in the city, it gradually drop down to a steady 23MPG until I recently reset it like two days ago and was reading 20MPG but now went up to 21MPG.

Reguardless, it did a hell of alot better than my GS300 i had previously which was probably 18. If on a good day.

 

A somewhat dirty Throttle Body will not lower your gas mileage. It will cause a little rough idle if it's real bad. At idle the TB is closed about 98%. The small opening at idle will not allow the air to enter as designed when it's real dirty.

A dirty MAF will cause poor mileage along with a O2 sensor that is erratic. An erratic sensor will not kick the MIL on in most cases. A defective one will though.

If one of your calipers is sticking you would notice a pretty noticeable pull to one side, so I would say that's out of the picture.

What type of plugs did your mechanic install and what was the condition of the old plugs? Plugs can give you a very good indication of how your engine is running.

FYI. Toyota uses ND plugs 100 % of the time now. I remember back in the 80's and 90's they would use NGK on one bank and ND on the other. We could never get a reason behind this from our factory rep at Toyota.

 

i have poor gas mileage here in ireland with all cars i had, im doing 12.5 US mpg in city drive on my ls 430, before i had toyota celica jdm with vvtli engine, i got just 14 US mpg in city!! I noticed that on the same car in other country you get much better mpg, even my friend on srt8 noticed the same thing, he had better mpg in france on his jeep than in ireland, so i think here in ireland petrol quality is *****e.

I was going crazy when i had celica, i did anykind of diagnostics tests and everything. Car was 100% perfect condition with no faults, but stilwas 14mpg on 1.8 liter motor

 

You guys from other countries must get a different blend of gas or something. Or...You have much different calculators.

 

Strange isn't it, especially as it's supposed to be 95% octane here. However, the roads in Ireland are really poor, and the type of driving i'm doing is short runs, stop and start, which is about the worst you can do for economy.

The plugs I changed for were NGK Laser Iridums. The previous plugs according to my mechanic were fine, and in his opinion, didn't need changing (but I did anyway)

 

i ordered denso tt plugs, see wats going to happen with mpg after i change them

 

I bought the car new off the showroom in Los Angeles. I have consistently logged the gas mileage of my 2004 LS400. I have city driving at 16 mpg and straight highway LA to Las Vegas consistently getting 26 mpg with premium gasoline. I never filled her up with regular gas.
Lately however, I have developed false electrical problem with the Tire sensor and a problem with my Air conditioning system. Other than that, with regular "expensive" dealer visits the car is just fine.

 

The LS430 gets wonderful gas mileage considering its weight, size and the luxury of having that big V8 on tap at all times.

But in city driving with short trips and lots of stop and go, the mileage is gonna be poor because of the simple physics of having to stop and start a very heavy car over and over.

On the open road at 70mph is where the LS really shines in terms of MPG given that it is a smooth riding giant boat.

 

I have an '04 LS430 with 120k. Engine is smooth as glass in park or neutral. a month ago I had the 120k service done with changing of the plugs...no real marked improvement in MPG, but I did get a bit better acceleration. I changed the tires and had it aligned this weekend and did see an improvement in the MPG, from 18.1 to 19.2.

 

If you're getting 13mpg (assuming you're calculating it properly) with normal driving, that tells me something is wrong.

I would say 90% of my miles are "city" miles and I average around 19-20 miles per gallon according to the in car calculator. If I do a lot of highway driving, it can go over 26 mpg.

I would maybe look at replacing your upstream oxygen sensors, over time, they can get "lazy" even though to the ECM they appear to be working properly. At the same time, I'm not one to advocate "shotgunning" parts at a problem, but many people would advocate changing the O2 sensors as part of a "tune up", even if there's no codes being thrown. Especially if they've never been changed and you're near 100k miles.