javanut467

Hi! I own a 1993 GS300 in GREAT condition. Everything is maintained and the oil is changed regularly. It has just hit 100,000 miles last week ( I got to watch it turn!).

Question: On the freeway I can easily get 18-20 miles per gallon depending on my mood. HOWEVER, in the city no matter how carefully I drive, I only get 9-max 10 mpg. Is this normal or is something wrong with the car?

If something is wrong, any hints on what could be the problem? I know the car is old but it has been WELL MAINTAINED. I just don't understand the huge disparity between city/hwy MPG.

Question #2 - Does anyone remember what the CITY/HWY MPG was when it was sold brand new? (Just idle curiosity.)

Cheers!

TheMole

iTrader: (13)

It was rated at 18/23 mpg when it came out.

How are you calculating your mpg between city/hwy?
Transmission fluid ok?

Kaiser

iTrader: (1)

My guess is that the heater element in the O2 is burned out and you aren't getting an accurate read unless the exhaust is at higher rpms and heat.

Is300Tree2

I would love to know how you are calculating the city driving.

deknick

my assumption is that the OP is calculating city MPG based on a common way.

i'm like that as well, i can go months without going on a highway, and in town MPG calcultaion is easy.

fill the tank of to full, reset the trip odomete, drive just like normal, then when you fill up,make sure you fill a full tank, then take the reading of the trip odometer, and how many miles you drove, then calculate that way, VERY easy to get the city readings, and if you drive on the highway t hat time, you just average it out to be highway/city driving. but if you are going to go on a trip on a highway, then fill up before hand. pretty simple IMO

javanut467

I calculate the mpg exactly as listed by DEKNICK. Maybe not the most accurate but it can't be that far off the ballpark.

Quote:" fill the tank to full, reset the trip odometer, drive just like normal, then when you fill up, make sure you fill to a full tank, then take the reading of the trip odometer, and how many miles you drove, then calculate that way..." Unquote I repeat the process for any highway driving. Both are separate. (i.e. I almost never have a reason to mix city and hwy driving.) I either fill up and drive around the city or fill up and take 100 mile+ drives out of town.

Transmission fluid as well as oil is check without fail every 3,000 miles. Remember in 18 years the total mileage on the car is 100K as of this month = 5,555 miles PER YEAR.

I am skeptical of the hwy mpg too. I drove 101.4 miles and used 3.1 gals going and 101.9 miles and used 3.4 gals coming back. There is no way this 3900#, 18 year old car is getting roughly 29 MPG. What I did do to "achieve" this kind of MPG was to drive btwn 55-58 mph (using the cruise control whenever possible) and tried not to vary in speed going up or down any hills. In two weeks I will make the exact same run and see what happens.

Question: IF the heater element were to burn out, wouldn't there be a warning light showing some type of malfunction? Recently replaced all oxygen sensors when they failed and the CHECK ENGINE light came on. If the heater element triggers the CHECK ENGINE light upon failure, then no, the heater element is not burnt out. O2 sensors were replaced last month and the mechanic made no mention of the heater element. If a diagnostic was run to find the first problem (i.e. O2 sensors) wouldn't he have readily found the heater element also?

To: THE MOLE, I imagine what you are most likely going to do is to tell me that I should write down an odometer reading, use the procedure I outlined above and after a period of time, take another odometer reading to get a more accurate MPG. Question: Obviously I can and will do that BUT what are the chances that the MPG is going to significantly change? I am getting 9-10MPG now. If I use the more detailed method over time, am I likely to see 18 MPG for city driving??

Thanks again to everyone for responding. I look forward to seeing what all of you think. CHEERS!

TheMole

iTrader: (13)

Nah my main curiousity was how you separated city from highway driving and you cleared it up. I have a 93 with roughly 140k on it and I average about 15-16 in the city. Not sure if it matters, but I usually fill-up at around 1/4 tank left. I know these cars are heavy and any full stops in the city will hinder the mpg. I think the least I ever got in the city was around 13 mpg with me stepping on it pretty good around town. No way am I expecting the 18 mpg considering the age of the vehicle. Curious to see what the issue is.

javanut467

To THE MOLE.

I am on the other end of the gas tank perspective. I never let my car go below 1/4 tank. I would kill to get those kinds of numbers. Driving a GS300 at a steady 55 mph is PAINFUL. I would love to let her fly (at least a bit more than 55)

It will be interesting to see if I can achieve 25+MPG again in two weeks time from strictly highway driving. Cheers for now.

Kaiser

iTrader: (1)

The heater element is built into the O2 sensor. An O2 sensor has to reach 900 degrees to function properly. The computer will still receive a signal from the O2 that is there, just not an accurate reading. Also, the ECU's built in 1994 are OBDI and completely stupid in comparison to newer computers. The fact that any check engine light comes on is amazing.
However, if they were replaced last month then they probably are good. Move on to the Karmen Sensor or fuel ECU in the trunk. You didn't try to clean the Karmen I hope.

rapollon

iTrader: (4)

http://www.fueleconomy.gov/feg/bymod...s_GS_300.shtml

TheMole

iTrader: (13)

It may not explain the discrepancy between city and highway driving and am just taking a guess, but since you are filling up when only 1/4 of a tank is used can it be due to bad/old gas?

Also, the pic in my sig contains a link to a log of almost all fill-ups since I got the car if you want to check it out.

javanut467

To: Kaiser, thanks, will do.
To: The Mole - you might be right. I have NEVER let the tank go below 3/4 empty and it has been YEARS literally since I have done that. As I don't get a chance to dr ive a lot it will take me awhile to empty her out. However, having said that I have been wanting to "let her fly" anyhoo. So on my next trip out of town, I'll just let her rip and inform the police officer who is writing me a ticket that I was simply trying to blow out the gas in my tank as suggested by THE MOLE. ha ha. Cheers for now.