Horrific Gas Mileage

[HunterXRen]

Hey guys,

I am having a major issue with my 04 IS300. The gas mileage has been horrific in the city compared to what it was getting previously. I have noticed a significant decrease of city mpg and I can visually see it going down tick by tick in maybe a fifteen minute commute from work. I used a up a quarter tank in one day, I think that is a bit excessive. My car is 59k mileage, but I thought spark plugs could have been an issue so I changed those with my timing belt, water pump and many other parts. I thought after changing my spark plugs everything would be fine again but it is not unfortunately. If anyone is having a similar problem or resolved this issue please reply back. Thanks in advance!

[smooth1]

So how bad is the gas mileage your referring to? Did you pull the 02 sensors and check those also? What about your fuel injectors? Do you have any codes or a cel?

[Parking17]

What's the temp outside in Virginia? If it's like freezing cold outside, it might be running rich. I live in So. Cal but believe it or not last year, we had some very cold mornings and I noticed the same thing, temporarily.

[HunterXRen]

Smooth1 I have no codes and I let a mechanic look at it and he has no clue also because no codes are showing up. He told me it's probably due to the cold weather outside, I am really hoping that is the situation.

[izzy300]

What kind of plugs did you use?? Iridiums are required for the 01s - probly the same for yours. Go to the dealer for any parts for your car, in other words...just a possibility if you let a friend do your plugs he might've used platinums which will change how the timing works. This in turn can affect mileage

[izzy300]

Premium gas, right??? Just making sure, sorry