Improving Fuel Mileage

[Sweet95LS400]

I want to first of all thanks everyone in this forum for the invaluable information I have recieved. I absolutely love my LS400, even though it is 10 years old, it really does drive and feel like a new car still.

Does anyone have any tips or tricks to helping improve fuel mileage?

I drive pretty conservatively, usually all shifts occur under 2000RPM in each gear. I have addressed a lot of maintenance issues like changing fluids and filters. Tire pressure is set correctly. I had used SeaFoam in the tank of other cars I have owned to clean up injectors, etc. That has always helped a little. The car runs like a top, but I want to get the best possible mileage I can. I think the very cold temperatures we have been getting lately have really affected the MPG I am getting. The plugs and wires are original, so maybe changing them out will help a little.

Has anyone done anything that has helped them get better mileage?

[KY350]

Sounds like you are doing everything correctly to get the best mileage out of the car.

One thing that I have noticed is that my mileage suffers by at least 10% if I run the air conditioning system continuously. So my suggestion is to only use it when needed to maximise your fuel economy.

Futhermore, try to us the air conditioning system at least a couple of time a week, even if just for 10 minutes at a time. This will ensure that the air cond system remains in good working condition and you will avoid regassing / leaks in the future.

[kcpth]

Definitely a tune up will help if u notice the mileage decreasing. I've yet to do mine... since it has been really cold here. I got my plugs n wiresets all ready... but just need to find the time n date to do it. Also... if ur O2 sensors r old n original like mine is... u may want to get it changed. It probably can go for a bit longer... as mine finally started to show signs of it crapping out. 14 years... n i never (or my father) changed the O2. My check engine light came on... wit a Code 25 i believe... so it's time to get it done. That should definitely help my lack of fuel economy.

Good luck.

[daffy]

Hi Sweet95LS400,

And don't forget to change out the caps and rotors when doing the tune-up. I took my in and this is one area they seem to forget to do. Mine had a miss every once in a while, otherwise it ran fine. Caps and rotors are cheap. Also change pcv valve. Daffy ;)

[maxed_out]

You are on the right track with good advice here..plugs, wires, rotors, caps. Buy the good stuff. Plat plugs etc.

Clean the Throttle body...procedure is well documented via a search.

Consider changing the fuel filter and air filter...make sure nothing blocking air flow into it.

Tranny flush wouldnt hurt if not done later. Diff too...

All for piece of mind.

I did mine recently and she can do 27-28 mpg.

Keep us posted.

[W201 sweden]

With all respect, I beg to differ on a couple of points stated.

A partly blocked fuel filter will not affect your MPG. At all.

A partly blocked air filter will not affect the MPG, unless it's REALLY bad.

However, these parts have a great impact on engine POWER! B)

Since efficiency in a gasoline engine is so low, it really pays off to minimize the power needed to propell the car.

In moderate speeds (below some 50 mph), friction between tires and road surface contributes alot to total energy loss. = MPG....

Selecting the a certain "low roll resistance" tire can give you a real saving - perhaps 5% or so. During the -80's, some european car manufacturers equipped their cars with these tires. The slightly higher price paid off several times, thanks to real life fuel savings.

A narrower tire (205/65 in stead of 225/60) will also save some fuel.

I think an incorrect wheel alignment can give you slightly increased fuel consumtion (2% or so?), due to the drag.

Also check that the brake pistons/pads retract fully! A somewhat dragging brake means real MPG loss.

Good luck!

[cardona6569]

Well an area worth checking is the gas cap rubber gasket. If you have not ever lubricated it have it replaced and lubricate it at least annually with engine oil very light. If it is too flat replaced, if you do not hear the air pressure coming out when you open the gas tank when the tank is not very full, change it anway as it might not be sealing properly. By doing this procedure you avoid losing gas by the avenue of evaporation.

Second always put gas in the car when the outside temp is the lowest, the gas lasts longer this way, when it hot outside it expands and burns quicker because it evaporates quicker. They even have a federal law saying this. They have to account in the price for the high temperatures, because the gas evaporates. You can also avoid this by parking your car in the shade in the daytime, thus keeping the gas cooler.

Clean your Mass Airflow Sensor.

Check all your wheels for free movement, to make sure all brake pads are not bidding.

***This one you research in the net.****

***Put 2 ounces of Pure, and repeat Pure Acetone in the gas tank for every 10 gallons of gas. Acetone makes the gas more volatile making it burn more percentage of it. Sometimes as much as 40% of the gasoline is not burned. In these vehicles I do not believe that percentage is that great on the LS, but much is not burned as the engines need to improve in this area.***

You can research it in the net. I put it to mine with about a 5% percent increase in the MPG this can vary from car to car due to driving habits, hill climbing gas flooring lol. When you try this you will feel the car stronger in the way it accelerates and its power. I would venture to say that with this you do not need to use Premium, but I always put premium in mine regardless, of the acetone.

Take all dead weight off the car, like the olde bowling ball, gulf clubs, etc. !If it is not needed in the trunk or interior of the car it needs to come out!

Hope this all helps.

C. PR