Milking Mpg Through Mods

[decypher]

I am looking to increase fuel efficiency in my ride. Power is not much of an issue as I would just like a little better MPG with some modding. What mods do you guys recommend for this?

To those who have already performed these mods, what kind of MPG do you get now? I average about 19-22 mpg right now and would love to see that number near 30.

[SKperformance]

A good intake , sea foam and an exhaust . I get 39 mpg on highway cruising.

[Randy&Bonnie]

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[Randy&Bonnie]

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[SKperformance]

I have a slightly different view of modifications.

This largest factor is how hard you press the gas pedal.

If you look far down the road and judge where and when to react with changes it saves a ton.

Also most all power adding modifications are to free power from centrifugal or vacuum forces so it can be used to turn the wheels.

So by reducing restrictions in the intake and exhaust , ensuring good combustion for a complete burn and having maximum air pressure in your tires to reduce rolling resistance. All of these things together will help you save tons of fuel.

FYI i have a full cold air intake with a ram pipe forcing air so it runs slightly lean , a full exhaust with X pipe. Lowered more than most , new iridium spark plugs , motul oil ($100) not run of the mill mobil1 , removal of the viscous clutch to an electric fan , Leds for all non braking lighting for reduced voltage , almost perfect alignment and a good coat of wax.

All of these things help bring my car above the standard for V8's never mind LS400's

[Randy&Bonnie]

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[Brendon Bosy]

39 MPG seems rather optimistic and unlikely (even my 4-banger Corolla couldn't get that high). I know some people think that mods to the exhaust and intake increase fuel efficiency, but its often not true. I've seen no change in my MPG. Think about it; if the auto industry knew it could increase fuel efficiency, don't you think they would have installed it? (and no, there is no grand conspiracy between the car makers and the oil companies).

If you really want to increase fuel efficiency, look at it from a more realistic/scientific approach:

1) Aerodynamics - A car lower to the ground reduces wind resistance from building up underneath your car. Also, if your SC doesn't have a spoiler, install a factory one. According to Lexus official specs, a factory spoiler reduced the coefficient of drag from .32 to .31

2) Weight - The EPA estimates that for every 10% of weight you reduce from your car, your fuel efficiency increases by 7%. Start by removing extranious junk, then remove the spare (it weighs 50 lbs). Don't fill your tank to the top (20.6 gallons is about 120 lbs). Try a CF hood (about 35-40 lbs savings) and lightweight seats (stock seats are 140 lbs combined). Try some lightweight rims to reduce rotational inertia. You could even go to the extreme, with CF doors, trunk, remove the sunroof, etc.

3) Tires - Don't go for those 20" uber-rims; it reduces fuel efficiency. If you want a sportier look without cutting fuel efficiency, go for 17" or 18". Next, raise the tire pressure. I normally run at about 40 psi. Most low end tires can go up to 44 psi and my Michillan pilots can go upto 51 psi. I've run the tires on both my Corolla and SC400 at 40 psi for the last 3 years and never suffered any issues with uneven treadwear. The only thing a lower psi gives you is a more confortable ride.

4) Driver - Aggressive driving can cut your MPG significantly. Accelerate slowly, brake as little as possible, and crawl to a red light. Also, don't use your a/c when you don't need it. Don't drive with the windows open on the highway. Use cruise control to stay at a constant speed. Its a natural human tendency to slowly increase your speed.

All that being said, here is the status and results for my car:

1997 SC400

EPA rated MPG: 18/23

Relevant info:

- 106,700 miles

- Custom straight-through exhaust

- Removed spare tire

- Never filled more than 1/2 tank of gas

- Has a spoiler

- Michillan Pilot sport a/s 225/55/16 tires at 40 psi each

MPG Results

Passive City driving: about 22 MPG

Aggressive City driving: about 14 MPG

Highway, cruise control 55 MPH: 32.5 MPG

Highway, cruise control 60 MPH: 31.1 MPG

Highway, cruise control 65 MPH: 30.1 MPG

Highway, cruise control 70 MPH: 28.7 MPG

Highway, cruise control 75 MPH: 26.4 MPG

Conclusion; with good driving and some practical, well proven "mods", its quite possible to beat the EPA. Don't sink your money into the fuel efficiency scams. Go with the proven facts and you'll see the results.

[SKperformance]

I hear it all the time as it is a far stretch from the norm of my cars mpg.

First i have a real time fuel meter giving me current stats. I can achieve that mpg at highway cruising not getting to highway speed or as a tank average mpg . Understanding that is the key that people fail to see. Unless you have a way to calculate your driving habits and usage you cannot determine how any modification works or if you are wasting gas by driving style.

All mods have been done by me. Air temps and humidity play a major role but i also live in a city more dense than most . Unknown to most in the world is that we have 16 lane highways with grid lock stop and go traffic for rush hour daily. Only L.A. and another city come close to congestion.

Also my 4 banger civic delivers the same mileage until it hits the highway which is where the LS sip gas and the civic does not.

I am on air suspension so i can go lower with little change , although i can raise the front end slight to cause a lifting of the front end and it can produce better mileage.

I get my best mileage at 40-50 km and 130 km

[decypher]

What kind of fuel meter would you suggest I get?

[SKperformance]

Mine is built into my 1998 LS400, so the display tells me

current fuel usgae

tank avg

total avg

km til empty

km travelled

time engine is running