Boltzmann

Some people purchase ethanol-free fuel. You definitely get better mpg's from 100% gasoline than with the 90% gas/10% ethanol most stations offer. The few times I tried the ethanol-free, 100% gasoline, I got a mileage bump of about 2-3 mpg.

That said, I still prefer the premium (91-93 octane) at Chevron (which is 90% gas, 10% ethanol, and has "techron" in it). It means I get a little less mileage out of a tank, but my RX seems to run smoother.

Boltzmann

My "sweet spot" is pretty close to 75 mph. Once I hit 75 mph, my mpg's just climb...

my2004rx

I have a 2004 RX330 AWD with 59K miles on it. I get 12 mpg streets and 17 freeway. I never got the mileage claimed on the sticker, but it was better than it is now. I have had the car for 10 years now (original owner, purchased Aug of 2013).
Gas mileage is abysmal. In my street driving I get 12 mpg. Highway 17. Almost 2 years ago I had major servicing done at the dealer and had all filters, etc changed along with other service. Even had timing belt changed since they had to do the labor to get to a leak anyway. I don't recall the mpg being as horrible back then, but I also wasn't on as tight of a budget, so wasn't as acutely aware of the gas cost.
The low gas mileage is not just a matter of what the computer says I'm getting. It's the actual figure based on doing the math. I use middle grade gas never the lowest. My last tank of gas I bought highest octane and have driven about 80% freeway (longer drive to vacation destination), and it looks like I will be getting 240-250 miles on the tank. Significantly higher than my around town numbers (200 miles to a tank), but still not great, especially for highway mileage.
I've been scanning through all the responses here, trying to decipher what might apply to my situation. I think the computer reading is accurate, so I'm not concerned about the computer reading. I am concerned with what is actually causing the poor mileage.

I do drive a lot around town, which gives me 12 mpg (I do drive mostly around town).
Freeway gets about 17.
Good tires inflated properly.

Any help is deeply appreciated!!!

Boltzmann

Have you replaced the various sensors (e.g., air/fuel ratio sensor, oxygen sensors)? I noticed that my mpg's increase after each replacement. For example, I changed my air/fuel ratio sensor just a couple months ago and my mpg's increased from ~ 23 mpg on the highway to 25+ mpg---the speed limit around here is 65 mph, which is lower than my car's "sweet spot" of 75 mph...I'm sure I could get better than 25 mpg if I drove at 75 mph---and my in-town driving improved, too.

All that said, AWD vehicles tend to get lower gas mileage than 2 wheel drive vehicles, though not as low as you're getting.

Good luck

utahrx300

Well after Lexus overhauling engine for sludge, I replaced the front and rear air fuel sensors and I'm averaging 23 mpg. The vehicle is driving perfect. Those sensors were 240$ a piece from lexus but well worth it.

bobschultz

just replaced my AF sensors, amazon at $109 each, and our average millage has gone up to 20 from 17. Its an easy DIY job, just search on the subject as there are great instructions out there.

Bob

Baetke

I replaced my A/F sensors with Denso 234-9009 sensors ($89 each) and improved my in town mileage from 19 to 21 mpg.

shumif1

I have a 2001 with 110,000 miles, i get about 25.2 to 26.3, that's city and highway combined . i drive about 30 miles a day.

kokoeduno

I just bought a used RX 300, 2000 model, odometer reading is 134,700 miles and there is 'CHECK' light on the dashboard. A very bad mileage of 9.5 MPG is shown on the dashboard.
Full tank can cover only 120-130 miles. Please somebody should help.

qwyktruk

I just purchased a really nice 2006 RX 400h with 32,700 miles!

I sell Lexus and took this in on trade for a new RX 450H . I drive 45-50 miles daily and am getting 2567 if I don't reset each day If I do the reset the mileage goes to 28.3

I guess my E430 is gonna sit for a while...lol

utahrx300

Yes, replace the two air fuel sensors on the exhaust manifolds. It was easy in my driveway. I only went with the stealorship (250$) price was in-store credit that lexus gave me.

Do A tune up as soon as possible. Spark plugs and air filter. Oil changes as much as possible.

Brcobrem

Hi,

I grabbed an Air/Fuel sensor from Rock Auto for $95 (now $ 125 I see). It is DENSO Part # 234-9009. It was an exact replacement. That part number is the same for the front (ie. A/F Sensor: Bank 2 Sensor 1) or rear exhaust manifold (ie. A/F Sensor: Bank 1 Sensor 1) . These are considered the "Upstream" sensors. If you get someone like Advance/Autozone to check your codes, they should see a code(s) P1133, P1135, P1150, P1153 or P1155 (although their non-Lexus testers will not have any clue as to what the codes mean).

Just for reference, Denso P/N 234-4206 or 234-4215 (exact OE replacement) is the Oxygen sensor (ie. Bank 1 Sensor 2). There is only one of these on the catalytic converter under the seats (in my 2WD RX300). It has a flange on it (as opposed to just threads)(or comes with a flange that you screw onto the threads). This one has many more holes in it than the air/fuel sensors do. This one will throw a code(s) P0135, P0136 and/or P0141.

Hope that helps someone (and helps me remember this the next time I need to).

Regards . . .

driver1988

Hello all. Back in May 2013 my RX was averaging 18.9mpg. I noticed that it has been dropping ever since. 3 months ago it was at 18.7mpg. last month it dropped to 18.5mpg. Now it's at 18.3mpg.

No CEL. The last time i had a CEL was for first bank O2 sensor in which i replaced back in Feb 2013.

Anybody notice this with their RX too? it's not alot but the decease seems consistent and so i suppose there's an issue. Don't want it to drop to 17 soon.


3.0 V6

125k miles

50/50 city hwy driving

hypervish

The most recent drop may be due to winter blend fuel.

Did you check your tire air pressure? This could definitely easily cause the minor mpg loss you are experiencing.

driver1988

Holy, so 2 days ago this happened.

I suspect a huge leak in my exhaust system. When accelerating, it's very loud under the hood. My gas mileage dropped from 18mpg to 11mpg. No check engine light.

In the past I have had rotted out gaskets but gas mileage never dropped that low and drastic.

Any suggestions?