I gotta chime in also. Mine is a 93 SC300 MT ... and I'm getting about 220-260 miles on 15 gallons. At one point, I was filling up twice a week ... costing me close to $250 a month just for gas.

I've changed the plugs, the wires, air filter. Nothing seems to work. Tires are set at 30psi in the front and 32 psi in the rear.

Any other ideas to help improve gas mileage??? This is costing me a fortune.

 

The biggest one I've seen (aside from the stuff you already mentioned) is the fuel filter.

 

A fuel filter causing poor gas mileage? Where have you seen that?

And those of you who say you "get XXX miles per tank" - that isn't saying much to the rest of us, since we all fill up and top off our tanks at different levels. Some states have vapor recovery nozzles, which cuts off at lower levels, and not all of us drive until the low level light comes on.

If you want to share, take a minute and do the math: Miles Driven / Fuel Used = MPG

 

Ive gone through 2 tanks since i bough thte car and that is about the mileage that im getting too. It sucks *****. Are you driving mostly "city" or highway type miles? Im mostly city type/stop-n-go type driving. And about 1/4 the miles are highway.

 

if the SC4's are getting 400miles to the tank on mainly highways, i believe the Sc3's should be getting at least 320 to the tank in the city, which i am 120 miles to the tank short.

so here are a list of possible reasons why: (gathered from the previous posts in this thread)
-happy foot
-types of gas used
-bad o2 sensor
-afm?
-fuel filter?

if anybody know more reasons why, copy and paste then add what you think it could be.

 

I would also like to know because my 93 gs300 gets horrilbe gas mileage..It runs great but doesn't do well in the MPG category...

 

Well, just as an update (1993 SC300 with 90k) I did a straight romp from DC to NYC. I was flying around 85mph and covered the distance on half a tank. Left Arlington, VA with a full tank and filled up at the Lombardi service station just off the NJ Turnpike and filled 10 gallons and some change. I calculated it to just over 20mpg. And I'm about due for my next major servicing. If I slowed down a bit, I could've probably push it up a bit...

 

i saw a huge jump in gas mileage once i changed the o2 sensors... mine failed around 60k miles or so and had them replaced and have not seen degradation in MPG in 40k+ miles since the change.
It could also be weak coil pack... not enough spark to completely ignite the AF mixture

 

How many of your 02 sensors dod you replace???

 

2 main(precat) and 2 sub (post cat)

4 in total.

I've heard you only need to change the 2 main ones as long as your cats are in good working order.

 

Thanks I can add that to the "to do" list .Aside from the MPG increase, did you notice any other improvements?Idle, speed...

 

so to maximize fuel effeciency, should i have overdrive / on or off, and have it in pwr, or ect mode?

 

i replaced mine because they went bad and was throwing the check engine/TRAC light.

I was getting about 17mpG and i've changed

ignition coil(factory)
ignition wires(factory)
all plugs(factory)
fuel filter(factory)
o2 sensors(factory)

now i average 21mpG

Differences have been
lower idle rpm (565rpm in gear at rest) (705rpm in park position) <--S-AFC readouts
smoother acceleration
almost no gasoline smell during warmup.

 

forgot to mention I used to pump 93octane

now i pump 87octane

car seems to not care.

 

rhino, from what i understand, O/D should be on while driving. and i think you should have driving settings on normal.

and thanks vssc400 for your experiences, i will definately remind my mechanic about these things.