kltw6

Hi, newbie here and I got my LS430 (made in 2004) for 10 months. Everything is good except the gas mileage. My average gas mileage is 11.6 MPG right now.


It is awful and someone told me that it could be carbon build-up? Can anyone give me some advice on how to deal with carbon build-up? Do I need to replace spark plug or anything?


Thanks a lot for your input.

DaveGS4

iTrader: (2)

Start with checking Tire pressures, clean air filter, clean throttle body and maf, spark plugs/tune up, disconnect battery.

Some threads

https://www.clublexus.com/forums/ls-...-1970s-v8.html
https://www.clublexus.com/forums/ls-...s-mileage.html
https://www.clublexus.com/forums/ls-...pointment.html

BMW7_LS430

What is the highway to local ratio?

LS430inDE.

Have you experienced the 11mpg since ownership, or has it recently reduced down to that? If recently reduced, was it gradually or sudden decline?

There's like a million variables (driver dependent) that could cause your poor fuel economy. Well, not a million, but like dozens.

In order to logically provide suggestions, please provide more details of the phenomenon. Odometer reading would be nice, specifics such as the 'type' of driving you're doing (city or highway), how much idling you do, the last time it was serviced including plugs and all the items DaveGS4 mentioned, etc, how heavy of a foot you have , and finally whether or not the LS is being used for taxi/Uber service in St. Louis would be a great start.

mrboca

Have your fuel trims checked through the OBD2 scan port..

Jabberwock

That is very low MPG for a 2004 unless you drive with a lead foot then it is what you should expect as the LS is a heavy car. My average for a mix of city and hwy driving is 21 mpg but I drive the car like an old geezer - very smooth and gently. As others posted check first - tire pressures, clean air filter, clean throttle body and MAF, spark plugs if past replacement mileage, disconnect battery. Also check thermostat, your temp gauge needle should be square in middle of gauge when the car is up to operating temp. If gauge shows low temp when up to operating temp you may need to replace thermostat.

fensterlip

Here's a relatively easy test. Check tire pressure, reset your mileage indicator and then drive like a geezer for a few days. See what difference that makes. If it's still real low then do all the filter checks. Still low? Then check the Mass Air Sensor, the filters and lastly have someone with a tester, or dealer, check the O2 sensors, plugs, etc.

Bocatrip

I too get terrible gas mileage and always have but I drive 95% city and do step on it. It's not unusual for me to get 12-13 mpg. It's fine as the car performs flawlessly, idles smotthly, and is still a comfortable ride after 122,000 miles. I drive around 5,000 miles a year so cost of fuel will not kill me. It's an aircraft carrier what can I expect?

Arcturus

These cars have a massive increase in fuel economy on the highway vs the city. If most of your driving is in the city, this may be the reason. However 12-13 mpg seems low. As others have stated, check the usual suspects (plugs, filter, MAF, etc). Then look at the O2 sensors. Sometimes these go bad without setting an indicator light and they are known to go wrong at higher mileage on this car.

BMW7_LS430

On 4 mile stop and go in 15-20 mins I used to get 11 mpg
On long trips I get 25 mpg.
Mixed I get 18-20 mpg.

OP is missing

Bocatrip

I do have the original plugs at 122,000 miles and one oxygen sensor has been replaced since my 5 years of ownership. After speaking to the service manager and shop foreman at Lexus, replacing the plugs ( if the car is performing fine) will not increase the gas mileage noticeably. I'm keeping my car because of reliability and comfort....not gas mileage. My 2010 Jaguar XK also gets in the very low teens with mostly city driving. V8s drink fuel.. My 2004 G35 (which I sold 2 years ago) got in the low to mid teens with mostly city driving and was a V6. Highway driving is a different story for most cars. A 1980 Lincoln Town Car will get 20-22 MPG with all highway driving and weighs as much as a freighter.

AJT123

If you're 90% stop and go that sounds about right, unfortunately. I lived smack dab middle of Los Angeles for 2 years where it's literally nothing but gridlock and never got above 10-13mpg. Now I'm back in wide open Tennessee and it's back to 19-20 mixed.

TANK47

It could be a number of things; how many miles and when was the car serviced last?