xirforever

I wonder if having your valves adjusted back to specs will make a noticable difference on MPG...

96ls400rt

I am a car dealer from New York, an early 90s LS 400 for 9700?? You could get a 98 for that price or maybe even newer.

HKSC430

bad wires connecting the stuff you have replaced?

not OE original equipment or cheap O2 sensors?

try to get an expert to see if your O2 sensors are giving the right readings in your car computer...

akxx

iTrader: (1)

Local/highway driving has a major impact on the 1UZ fuel economy.
Around town, very short trips I get 15mpg. On the highway I'm getting 26mpg.

Suneet

Akxx, you're gettign 26 mpg on your first gen? That is ridiculous. What is your secret? How many miles on your car? I get 20 if I'm lucky.

I was getting even worse than that, but I had a faulty ignition coil. Now I"m back up to about 20 on the highway, 16 in the city.

steveski

Can't imagine why some get such poor mileage. It is probably not one thing but rather a mix. I get 22-25 average per tank (city and highway) and usually go between 450-475 miles between fill ups. This is on my 95 with 184,000 miles. I do use Sea Foam every 5,000 miles and use Shell premium so my setup is clean.

akxx

iTrader: (1)

I dunno what the secret is, other than a properly functioning engine. Keep in mind it only has 85k miles on it, and has been meticulously maintained.

richonenz

I would be pulling the injectors out and having them serviced and bench tested to make sure they have the right spray pattern .
After all they are the coal face , doesn't mater how well everything else is working if the injectors are poviding a poor spray pattern .
Yes your car might have low miles but it is still 14 years old !!
Also fit some new STI leads if you haven't fitted new leads already .

steveski

At minimum I would try a $5 can of Sea Foam as it could only help.

Suneet

Yeah I've run seafoam through the gas tank as well as through the throttle body, and I ran it through the crankcase on the last oil change.

People seem to still debate wether it fouls the spark plugs or not.. and so I'm not going to run it in the crank case for a while. At the last oil change I had all my plugs, wires, distributor caps, rotors, and ignition coils changed..

omarg

I got 29mpg with my ls400 no joke. I did a little experiment. I was super light on the throttle, anticipated stop lights, used cruise control, i increased tire pressure to 34 all way round, no ac and max speed of 60. I use mobil one too. I'm sure that helps a little bit.

I did another run for comparison. Hard on the throttle, ac blasting, 80-90 with cruise, lots of truck passing. Avg 24mpg.

so if i drive normal i can expect 25-26. Pretty good for an old v8.

93 octane Premium gas only. I refuse to even try regular. I just don't believe the savings. I expect max performance from my car. 65$ fillups do suck though.

pCYYC

richonenz

I'll say it [ type it actually !! ] one more time for the slow/mentally impared people !!
GET YOUR INJECTORS DONE !!!!!
That is where it all HAPPENS , all the other stuff helps BUT it's not the MAIN GAME !!
New pre cat oxy sensors and the injectors ARE the main game !!
Do what I did and pick up a secondhand set of injectors , they are relatively cheap to come by , get them reco'ed and bench tested [ as they should when they reco them ] and then do the big swap over...too easy .
See if the injectors aren't right it doesn't matter what else you do , you are not going to get good mileage .

Thermactor

iTrader: (1)

the key to good mileage lies EXCLUSIVELY with the driver and his driving technique. Driving 73mph with the cruise on gives me an average of 22mpg in my '96 LS400. Driving according to the Scangauge and throwing it in neutral on downhill slopes gives me upwards of 31mpg on the highway. And my car has 245,000 miles. Imagine if it was brand new!

PureDrifter

iTrader: (10)

true, driving like i do sometimes (i live in a hilly area and know a few good spots) can net ~13-15mpg

Suneet

I agree that the driver makes a difference, I know first hand, I own a prius! Our family compets to see who can get the best mileage

However, a 10MPG difference? Thats almost a 50% increase.. and I know I don't drive with a lead foot. I don't think I could get an increase like that by driving better. I know, becuase the best mileage I have ever gotten was 410 miles to a tank (20 gallons of gas), when I was driving from San Jose to San Diego.. 70 MPH all the way, relatively flat.

I think next up on my list of maintenance, once I finally finish my audio install, will be to replace the O2 sensors with the Walker aftermaket sensors. After that, I will look into buying new injectors. How much would this cost, and what is the labor on installing new ones? Where can I get my injectors "tested"? I need to learn more about this , as I don't really know anything at all.