Yamaheart

My 2003 GS 300 is getting worst with gas mileage. Its get about 300 or less to a tank now. I change oil regularly and maintain the car pretty well. I had to replaced one of the O2/Fuel air sensor not too long ago. I think I might have to replace all 4 O2/fuel air sensors. What do you guys think? Please help.

PATDOW1

There are so many variables when it comes to fuel economy. You are already tackling one of the culprits (02 sensors).
I have also included a few more culprits listed below to consider/check (OBDII scanner).

• Tire pressure
• Dirty/Failing Fuel Injectors
• Dirty Air Filter
• Worn Spark Plugs
• Heavier wheel/tire combo
• Audio System
• Timing
• TPS Sensors/MAF Sensor/EGR, etc, etc

Good Luck!

Bullitt180

Damn I wish I got 300 miles on a full tank in my GS430. I usually get 230ish, 250 if I'm lucky when the fuel light comes on, so I'm averaging 14-17mpg with 90% city and 10% highway in Florida.

bruceb58

is that 300 miles with 18 gallons or 300 miles with 16 gallons. Highway or city driving? Kinda hard to help you when you give so little info.

Bullitt180

What are the 16 and 18 referring to? It's basically a 20 gallon tank.

isfdude

iTrader: (11)

Maybe a good tune up and check the wheel alignment.

bruceb58

it's an 18 1/2 gallon tank. We have no idea how much gas he is using is my point.

Bhubb18

It depends if you're getting a full tank. My gauge is a bit iffy (and I park on a steep hill), so when the car says its empty I still have a fair bit of fuel left. I average 12L/100km, so around 20ish MPG, but I give my car a bit of a spanking

Yamaheart

Sorry for the late response, and thank you for this fast supports from all of you guys.

I'm actually getting about 250 miles per tank, I'm average about 18 MPG per my screen. Im driving Highway most of the time. The car seems to have a quick jerk to it when you step on the gas pedal, not smooth as it used to be. I do have Coilovers on my car.
My alignment appears to be fine, the car drives straight.
I have stock tires which is 225/55, pretty much stock.

A while ago, one of my O2/Fuel Air failed, I had that replaced, some how it came back but i was able to clear it out with the OBD 2 and it never came back ever since.

I do believe my Spark plugs are failing and require to be replace.
I'm gonna check my air filter also.


How do I check to see if I have Dirty/Failing fuel injectors?
How do check for the MAF, EGR?

Thanks guys

PATDOW1

The only real way to check injectors is to remove them and have them cleaned and mapped or buy new ones.

For the MAF and EGR head to your local Autozone and have them run a OBDII scan on your car to see if you get any codes. EGR is cheap to replace it's the MAF that will be quite a bit more depending on where you get it from. CRC makes a spray can cleaner that I heard works well

dreamcar88

iTrader: (1)

i usually get around 300 miles per tank gs300 mostly suburbs / some highway

bruceb58

I get anywhere from 18 to 22 depending if it's city or hwy. You really aren't that far off at 18. I assume you are using premium fuel because using regular will knock off 1-2MPG.

Measure the miles you drive and use the amount you fill up your tank. I never trust the mileage indicators from an on board system.

Air filter does not affect mileage on a fuel injected car.

Mcon

iTrader: (1)

My baby gives me 355 miles in the city and the empty light start turning ON. With only 16.5 galon and 93. I thinks is good.

Bullitt180

Again, I don't know where you're getting your information, but the fuel tank capacity is 19.8 gallons which is why I said basically 20gal.

They were rated from the factory at 16mpg city and 23mpg highway, so 18 isn't far off......there is only one problem....if you're getting 18mpg, it's mathematically impossible for you to only get 250 miles. 250 miles at 18mpg would only use up 13.8 gallons, so you would have around 6 gallons left which would put your gauge a little above a quarter tank. I know I get 230-250 miles on a full tank at 14-15mpg. One of the consequences of having a 2GS in Florida, even if I baby mine, the best I can hope for is about 16mpg with a good mix of city/highway.

Mcon

iTrader: (1)

Bullit180,

I agree with you 100% and I'm in Florida as well. Unless you are an aggressive driver and why does the mileage that want or expect ..