TMaxxTim

Hey guys. I get like 13-14mpg on my 92 SC 300! Its horrible! I've tried the fuel system cleaners, fuel injector cleaners, whatever you want to call them.
Nothing seems to work. I consistantly get this milage and if I do long interstate trips the most I've gotten is 17.6mpg, thats cruising about 75mph at 3200rpm.

BTW, My car is a 5spd, which I thought got better milage than automatics!

Anyways my car runs great besides for this, my engine compression is good, I don't know what it could be! Is this the milage you other people get??

I mean I do floor it on occasion, but for 1 tank of gas I made sure I didn't do that and tried to see what I would get and I think I got 14mpg instead. I'll shift around 2700-3200rpm.

Any ideas/suggestions! Every $36 fillup every 220miles is KILLING ME!!! The most I've gotten is 280 miles out of tank and that was on the interstate trip!

newyorksc

have you changed your spark plugs ?

T0ked

iTrader: (2)

Mileage on the car? Last time you did a full tune up (cap, rotor, wires, plugs)? Cleaned MAF sensor, TB? O2 Sensors? It could be a lot of things... Keep in mind, the I6 never really got great mileage. I occasionally get 14mpg. Usual is 16-18mpg around the city and around 22-24mpg on the highway.

TMaxxTim

The car has 145k on it. The spark plugs were changed around 142k right when I got the car. Cap Rotor and Wires were done right before I got the car. Not sure on o2 sensors or MAF sensor (what do you do to clean that??). I thought o2 sensors only went bad when teh check engine went on.

I just wnat a couple extra mpg, maybe 280 out of my tank consistantly in the city! It just kills me to lay down $36 a tank every week, and yes I use 93 gas all the time, never once have I put in lower octane.

BTW Spark Plugs are NKG Iridiums, so top of the line there.

O. L. T.

iTrader: (17)

HUGE thread on this, do a search.

Engine question =moved.

TMaxxTim

I have but I didn't really see any information in that thread other than fuel cleaners and basic tune-up. And it seemed more centered around the V8, not the I6 which I have. Thought there may be different things to try on the 2JZ

blksc300mt

I was wondering the same thing about the mileage. My 5 speed will probably do at best less than 17-18mpg @ 80-85 on the highway. I was expecting much better. Checked one or two of the spark plugs...they looked fine...maybe i should change them anyway? My car has about 148k miles

Kilo

I have a 92 5spd, w/ roughly the same miles, and I experience the same **** poor MPG as you. If you ever figure out how to increase your mpg. please let me know.

blksc300mt

I think that the o2 sensor might be the problem. ive heard that an old o2 sensor makes the car run too rich.

TMaxxTim

The O2 sensors are the only thing that make sense to me by making the car run rich. O2 Sensors are an expensive thing to guess on and might not even help in the end!

Would adjusting the valves have anything to do with it? I have a slight slight tapping whenever I get on the gas.

I just don't understand how the V8's get better milage and especially other V6's!! I would think our engines would be the same as other 6cyl engines.

Do the GS300's and IS 300's get the same milage as us, or does the VVTI and newer engines make a big difference?

ajs14

Fuel filter? Clogged cat? Larger diameter wheels don't help either...

LexAnt

iTrader: (2)

well the thing is with the V8, the highest i ever go is 2k rpm, city driving, if i'm on the freeway, at 75mph, i'm cruising only at 2500rpm. Try shifting at 2k or slightly below? like around 1750-2000rpms? Keep in mind the I6 engine may have to work harder to compensate for the torque the V8 has. Man if ya hate the gas mileage now, don't go turbo

TMaxxTim

Thx for the suggestion but its hard to shift around 2000 or less. The car has no get-up and go. I'm just saying in general it should be better milage overall. My friend has a 400 and gets better milage than me and I KNOW he doesn't keep it around 2000rpms!! I'll look into the filters and intake manifold cleaning.

newyorksc

You would be wasting more gas if you shift at that RPM.
What your doing is fine, in terms of shifting, 2700-3200 rpm.

Buttercup

If your car is running really rich, a person in another car should be able to see some smoke, at least when shifting.

Check air filter, but I doubt that's the culprit for 7 mpg.

Tire air pressure, should be around 30-35 psi.

I've taken off the black intake piping and drenched the throttle body with some air intake cleaner, which is found at auto stores, and then put everything back and start the car after a few tries. It should help clean some gunk from the throttle body down to the intake manifolds and valves. If it doesn't improve gas mileage, at least it'll increase throttle response.

It could be the EGR system or PCV valve.

What's your start up idle, and what's the lowest rpm it settles down to when warmed up? No reason for this question, just to see if there's a discrepancy.