Bdragon007

Thank you all for your thoughtful responses, usermel brought up a lot of good points. I do think of myself as a easy driver (days of turbo charge GS is over), but unfortunately the short trip I go to work everyday is full of red lights. I'll try to go another the longer route but with less lights and see if it help. In the mean time, if anyone had prior experience with improving your economy please chime in. Thanks again!

Bdragon007

I'm also on 20", but I make sure with the tire the whold wheel diameter is the exact same with factory. Hear your 500 miles tank make me want to cry jk

Cape Cod

Lexus dealer tune ups cost 2 times the money, where as your car is not in warranty maybe you can go to Lexus and get it checked out. I paid $90 last week and they did a complete inspection, the same as they would bill themselves $280 to certify a pre owned car. let them know your specific concerns and they will address them. Then if it makes financial sense, get the work done somewhere else.

I believe Lexus is the best and only hires the best service people. Even if you go to Toyota you'll get a good but lesser service.

The things that most make sense to me is the o2 sensor, fuel filter, tire pressure, all have been mentioned. Is the car giving full smooth power?

Good luck,

-Nile

Lexophile

Hi Again!
I bought the SK20R11 Denso long life plugs from Rock Auto, these have a gap of 0.7mm as opposed to the Power performance plugs (gap 0.4mm)which, I reason, will almost surely increase MPG. Another tip is use cruise whenever safe to do so. I can see the current MPG go higher as I switch to cruise. It figures that the computer is more sensitive than my right foot!

Good Luck!

Bdragon007

Nile,
I don't think it the o2 sensor since check engine light is not on, car run smooth but on kinda wierd on the start. It feel like it try to down shift everytime you get on the gas at a complete stop. I search the forum and I guess I'll try to clear the ECU.

Bdragon007

Thanks for the information, I think I'll invest in some plugs first to see if it makes any different.

Cape Cod

The other thing I thought of while driving today is that I just came from INF M35X and your coming from a LEX GS. I think were accustom to 0-30mph a little faster than some ls drivers. Even though you don't think your driving aggressively in comparison to the GS, it may be that were accustom to faster than average speeds "plus I know I drive aggressive". My car is an 05 w/ 13,500 miles and I average 14.5mpg and I know my car is capable of much better.

Just my thought,

-Nile

Bdragon007

So if your car is much newer and has 6sp tranny and does 14.5 mpg then I guess my milage is about right, which mean I'm screw. Now let see what other thing I can cut out to make up for the gas bill.

feldman

Definitely get a tune up and use premium gasoline. Using regular is false economy as the ignition timing is retarded and you waste money.

You might also consider switching to 16" rims, as these will provide slightly better gas mileage because less rubber is on the road.

I can get 12.5 mpg in my car if I sit in my driveway with the air conditioning on ('05 LS430). My kid likes to 'drive' the car while on my lap. It destroys the gas mileage for the tank if you do it a lot (a lot meaning 5-10 hours per week). Otherwise I get 27mpg on pure highway driving, about 15-16mpg in the city, depending on how long we 'drive' while parked. I'm riding on stock 17s, having switched from 18s because the ride was too harsh.

Also if you have anything heavy in the trunk leave it in the garage. It makes a difference.

CarguyinGa

Timing will only retard when under acceleration and the knock sensors detect pre-ignition, under a cruise state it won't happen. Using regular is fine, everyone can spend as they see fit, but the cost per mile is lower with regular.

Restricted air or fuel filters will not reduce mileage. They will reduce peak power output though. Airflow calculations are done by a mass air sensor in the intake duct, injection duration is based upon this signal, if the air filter is partially restricted the peak air flow rate will be lower and injector on time is reduced to match the incoming airflow.....power loss, not efficiency loss. Restricted fuel filter will be evident during hard acceleration, the engine management system is depending on a preset fuel map during acceleration but is able to use oxygen sensor feedback during cruise conditions and compensate for a lower fuel supply, again...no loss of efficiency but a loss of power.

Spark plugs are merely a set of insulated electrodes that allow secondary ignition voltage to jump a gap resulting in a spark to ignite the air/fuel mix. If the engine is not misfiring, there is no magic to be had from changing them.


Low tire pressure is probably the #1 cause of wasted fuel, make sure to keep them at the high side of specs for the car, the tire is most likely rated to handle 44 PSI, the car specs will be lower in most all cases. You can inflate them to the max pressure on the sidewall, the possible side effects will be a harsher ride and maybe increased tire wear in the center of the tread.

Synthetic oils can increase economy some due to lower friction. It's not cost effective though and if you decide to use synthetic oil you should use engine longevity as the basis for that descision.

Another thing to remember is that a car sitting still always gets 0 mpg, it's using fuel while not moving, it'll also be much lower in creeping traffic where you are unable to get in and maintain higher gears. The engine is an air pump basically, fuel is added in proportion to the air and a spark is introduced to ignite the mixture at the right time. If the engine is turning 2000 rpm in 1st or 2nd gear, it's not under quite as much load as it is in 5th gear but the overall consumption rate per mile is higher. The only way to evaluate the actual efficiency of it is to do a strict highway drive on the flattest roads possible. Reset the avg and drive it at least 10 miles at a set speed. That will give a solid reference of what the real mileage is that the car can achieve. Look for that to be in the 23 to 25 mpg zone. If it is, your driving conditions are the culprit for the lower overall figure.

I'm not meaning this in a bad way, but, the mileage should not be a big factor in the descision to but this car, it's a LUXURY car, not an econobox.

feldman

agree with everything that you said above (especially about tire pressure), but our cost per mile on both our RX350 and our LS430 appear to be better with 93 octane than 87. This is COST per mile. You are right that timing is only retarded while under load, but to get a car to move the engine must be under load.

Also if plugs aren't firing or are firing intermittantly I believe you'll blow out unburnt fuel, and get lower mileage.

CarguyinGa

Since fuel prices have risen drastically and the standard 20 cents a gallon upcharge for premium is a lower percentage, it may be closer now.

That was my reference to misfiring, you'll definitely feel it when a misfire occurs and OBDII compliant cars monitor for misfires. When misfires accumulate to a small level even on a single cylinder, the service engine light will illuminate.