I want to get to the bottom of this ... why is my gas mileage BAD?!
 

Alright, I want to get to the bottom of my poor gas mileage and will do whatever to obtain the advertised 17+ mpg on my car. I know there are many threads on this topic so I am sorry for it's repeat.

Things I have done since buying my RX300 during July of 2011 @ 174,000 miles (now it's at 178,000+ miles)

- Set of four new tires
- Wheel Alignment
- Tire balancing
- Transmission ATF Drain & Fill
- Front & Rear Dif. Fluid
- Brake Fluid Flush
- Power Steering Flush
- New brakes and pads on the front two wheels.
- Did my own oil change with Bosch Oil Filter and Mobil 1 Synthetic 0w-30 oil.
- Transfer Case Fluid
- Changed my Cabin Air Filter and Engine Air Filter
- Replaced front two strut mounts and front two sway bar links (due to it's rattling noise).
- Poured Seafoam through the PCV.
- Cleaned throttle body.
- Cleaned MAF Sensor


Things I should note:

- Carfax states the cars spark plugs were changed at 125k miles along with it's timing belt.
- The rear brakes will need to get changed soon. (Probably good for another year or so).
- Struts were never changed. Ride is pretty bouncy sometimes. Doubt it affects MPG.
- Fuel System Cleaning was done for free from my friend whom works at Merchants.
- Unplugged my battery for 10+ minutes.

I also checked if I had any CEL's ... but nothing showed up.

& yet, I am averaging 14-14.5 MPG. Why is that?

I see everybody else who averages 17+ mpg easily. Even hypervish averages 19.2mpg if I recall correctly.

Only reason I want to get to the bottom of this is because I am going to get a job that will require 35 mile commute each way (opposed to 2 miles at the moment at my current job).

Thank you guys for understanding.

Kind regards.

You forgot to clean the MAF sensor.. It's a load sensor.

My mistake, I forgot to mention that too. I cleaned that as well.

What fuel grade are you using?

You need at least 10miles of commute (with mixed stop & go) to even consider the MPG data to be valid. With 2miles, your engine is running rich most of the time.

I would suggest go on longer drive 50+miles and record new data. Or even do a mock commute.

Salim

This.
A cold engine wastes a lot of gas.

Take a long trip and record mpg.

Maybe that is why. Because I usually just start the car and leave the driveway.

Once I get on the road outside my house (speed limit 35) ... I usually go 40 and the RPM will be around 2500 - 4000 since overdrive doesn't kick in until the engine temp reaches the line? So that kills gas?

I will record a long trip data one day. Usually the highest I've obtained recently in a 35 mile trip was 16.7 gallons.

Another question is what is the true definition of highway mpg? Like 2 hours nonstop driving at a speed of like 60mph orrr?

Just curious because the car is advertised around 22 or 23 highway mpg

I'm also having same problem and I'm getting about 17mpg with 80% highway. Not sure what to do to get better gas millage.

In my opinion this is the cause of transmission problem. Every attempt (other than a safety concern) should be made not to go over 3K rpm till the temp reaches operating temperature.

The specified rating has lot of woodoo in it. Last year US laws tried to standardize it a bit better. With ethanol in gas, the mpg got lot worse.

Salim

So pretty much, are you suggesting me to warm up my car before hitting the streets? Seems like 75% of the forum doesn't.

I should also note I always drive in PWR mode, not sure if that makes a difference.

I warm up my car, at least 4-5 minutes in the winter time. In the summer, I give it about 30 seconds - 1 minute and it's usually good to go, and overdrive will be available.

Driving in PWR mode, holds gears longer, and downshifts quicker.

But, I too wait till the temperature gauge shows it's at the first line. At that point overdrive is enabled. For example, at my house in Michigan, I live off of a road that has a 55 mph, so instead of jumping straight onto that I will turn out of my street, and into another street and drive around the neighborhood till the car is warmed up enough to get into overdrive.

If I can't get up to operating temperate, due to whatever reason, I will keep the rpm's below 3k to avoid any damage.

Please refer to the owner's manual.

Start and drive. Every thing will warm up quicker and not just the engine block. Just dont exceed 3000 rpm till norm operating temp is reached.

The other Fuel hog is the pwr mode. It tends to keep you in gear longer and you get more power to the wheels at expense of fuel economy.

Salim

Okay, that is great to know. I've always thought it was okay to drive at whatever RPM (regardless of engine temperature) as long it doesn't hit the red line. Do you drive on power mode?

I'll try my best to leave the house earlier so I can warm up the engine. I've always thought it was pointless to warm up the engine because technically you're wasting gas @ 0mpg.

I'll try to take off the power mode and leave the driveway without warming up the car and see how that goes. I'll also make sure not to exceed 3000 rpm and see how that turns out.

It is a waste of gas, because only the engine oil is warming up, nothing else is getting warmed up. I still warm it up, because it's a habit. lol But, it's good to warm it up at least 30 seconds, I warm it up more than necessary. I say 30 seconds because that's enough time for the oil to make it's way around the engine. But, yes definitely try and keep the rpm's below 3k.

I do use power mode on occasion. Usually when I feel like driving spirited! :P lol

Do you still have the original Oxygen Sensors? If so, you should consider replacing them. That could be a contributing factor to the bad MPG.