Is 14.3 MPG bad for a 2007 IS350? - Lexus IS Forum
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post #1 of 28 (permalink) Old 11-08-2010, 09:20 PM Thread Starter
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Is 14.3 MPG bad for a 2007 IS350?

I just got a used 2007 Lexus IS350 last month as my first car. After driving it to school for about a few weeks, I realized I only get 14.3 MPG and had to refill 3 times already. Is it normal for the IS350? I drive about 25 miles a day, 10 being on the highway. Is there anything I can do to increase gas mileage? Thanks!
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post #2 of 28 (permalink) Old 11-08-2010, 09:26 PM
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Originally Posted by chi123 View Post
Is there anything I can do to increase gas mileage? Thanks!
Yes, relax on the gas pedal speedracer.

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post #3 of 28 (permalink) Old 11-08-2010, 09:43 PM
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Yes, relax on the gas pedal speedracer.
This. I get around that in my IS300 in SF (Hills, hills, hills).
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post #4 of 28 (permalink) Old 11-08-2010, 11:45 PM
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That sucks for an IS 350. Now I don't feel so bad for getting 21 mpg on my IS 300.

Are you keeping up with the scheduled maintenance?
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post #5 of 28 (permalink) Old 11-08-2010, 11:45 PM
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I got 28 mpg on my trip to the smokies including lots of mountain driving.

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post #6 of 28 (permalink) Old 11-09-2010, 06:39 AM
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I got 28 mpg on my trip to the smokies including lots of mountain driving.
Yeah... me too... (same trip even, to the smokies!).

I routinely get 27-29 mpg on highway trips and 21-23 in city driving.


14.3 is awful

Like, there's something wrong with the car awful. (assuming you're not constantly flooring the gas/slamming the brake 100% of the time)


First cheapest/easiest things to check are the air filter and tire inflation. If it was never changed and is badly clogged then changing it would greatly improve mileage... also check your tires are properly inflated (though your mileage problem is bigger than I'd expect just underinflated tires to cause)

Checking/cleaning your MAF would be another thing, this is slightly less easy than the two above, but is mostly free (couple bucks for cleaner).

Beyond that- how many miles on the car? Spark plugs are called to be changed at 60k miles, and bad plugs will certainly kill mileage too... Do the other things first though as they're cheap and easy, changing your plugs are considerably less so. Ditto the front O2 sensors, a bad one will hurt mileage a lot, but it's not cheap to replace (though you're probably still under warranty there, and a bad one OUGHT to throw a CEL)
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post #7 of 28 (permalink) Old 11-09-2010, 07:43 AM
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Originally Posted by Knightshade View Post
Yeah... me too... (same trip even, to the smokies!).

I routinely get 27-29 mpg on highway trips and 21-23 in city driving.


14.3 is awful

Like, there's something wrong with the car awful. (assuming you're not constantly flooring the gas/slamming the brake 100% of the time)


First cheapest/easiest things to check are the air filter and tire inflation. If it was never changed and is badly clogged then changing it would greatly improve mileage... also check your tires are properly inflated (though your mileage problem is bigger than I'd expect just underinflated tires to cause)

Checking/cleaning your MAF would be another thing, this is slightly less easy than the two above, but is mostly free (couple bucks for cleaner).

Beyond that- how many miles on the car? Spark plugs are called to be changed at 60k miles, and bad plugs will certainly kill mileage too... Do the other things first though as they're cheap and easy, changing your plugs are considerably less so. Ditto the front O2 sensors, a bad one will hurt mileage a lot, but it's not cheap to replace (though you're probably still under warranty there, and a bad one OUGHT to throw a CEL)
Any chance it could be a defective ECU?

When mine went on my car, I noticed that mileage went down the tank (although that car had so many issues, tough to use it as an example).

I average right around 22mpg. Most of my driving is city. If I do drive for extended periods on the highway I can get 28.

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post #8 of 28 (permalink) Old 11-09-2010, 11:01 AM
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Any chance it could be a defective ECU?

When mine went on my car, I noticed that mileage went down the tank (although that car had so many issues, tough to use it as an example).

I average right around 22mpg. Most of my driving is city. If I do drive for extended periods on the highway I can get 28.
It's possible, but as you note there'd likely be more issues than just poor mileage from that (and it's a bit tougher for someone without a spare, known good, ECU to diagnose than a lot of the other more likely possibilities I mention)
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post #9 of 28 (permalink) Old 11-09-2010, 10:15 PM Thread Starter
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Originally Posted by Knightshade View Post
Yeah... me too... (same trip even, to the smokies!).

I routinely get 27-29 mpg on highway trips and 21-23 in city driving.


14.3 is awful

Like, there's something wrong with the car awful. (assuming you're not constantly flooring the gas/slamming the brake 100% of the time)


First cheapest/easiest things to check are the air filter and tire inflation. If it was never changed and is badly clogged then changing it would greatly improve mileage... also check your tires are properly inflated (though your mileage problem is bigger than I'd expect just underinflated tires to cause)

Checking/cleaning your MAF would be another thing, this is slightly less easy than the two above, but is mostly free (couple bucks for cleaner).

Beyond that- how many miles on the car? Spark plugs are called to be changed at 60k miles, and bad plugs will certainly kill mileage too... Do the other things first though as they're cheap and easy, changing your plugs are considerably less so. Ditto the front O2 sensors, a bad one will hurt mileage a lot, but it's not cheap to replace (though you're probably still under warranty there, and a bad one OUGHT to throw a CEL)
I brought the car with 49,310 miles on it for $20,300. In the month I had it, put like 500 miles on it. When I went to replace the air filter, I found a clean air filter inside, same thing with the engine oil, fresh oil was inside. I just replaced the differential fluid and had the dealer flush out the brake fluid and coolant so it's updated with maintenance. I'll probably get the spark plugs replaced before winter comes in. About the tire pressure, it's at 33 psi on the front and 34 psi on the rear, that's a normal drop I guess since it's like 40 degrees outside now in the mornings.

Also, I don't accelerate hard or brake, only at like 3000 rpm at most. You think if I brought it to the dealers, they can diagnose what's up with the bad gas mileage?
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post #10 of 28 (permalink) Old 11-10-2010, 06:30 AM
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Originally Posted by chi123 View Post
I brought the car with 49,310 miles on it for $20,300. In the month I had it, put like 500 miles on it. When I went to replace the air filter, I found a clean air filter inside, same thing with the engine oil, fresh oil was inside. I just replaced the differential fluid and had the dealer flush out the brake fluid and coolant so it's updated with maintenance. I'll probably get the spark plugs replaced before winter comes in. About the tire pressure, it's at 33 psi on the front and 34 psi on the rear, that's a normal drop I guess since it's like 40 degrees outside now in the mornings.

Also, I don't accelerate hard or brake, only at like 3000 rpm at most. You think if I brought it to the dealers, they can diagnose what's up with the bad gas mileage?
They SHOULD, but it depends on the dealer really... some will just shrug and say "No warning lights, no noises, so it's fine" and some will actually try and help you.

Worth a shot though if they're willing... do it quick though as unless you bought an extended one you're just about out of warranty (50k miles) on anything besides powertrain.

I'd probably put a bit more air in those tires, but that's not nearly enough of an issue to cause that kinda mileage hit.
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post #11 of 28 (permalink) Old 11-11-2010, 12:58 AM
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These cars are six cylinders expect to pay more for gas .

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post #12 of 28 (permalink) Old 11-11-2010, 07:30 AM
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These cars are six cylinders expect to pay more for gas .
Huh????

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post #13 of 28 (permalink) Old 11-11-2010, 08:18 AM
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These cars are six cylinders expect to pay more for gas .
I don't see the point here. If most people are getting in the mid to high twenties mpg, and this guy is getting 14 mpg from a similar car, then he's definitely got a problem.

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post #14 of 28 (permalink) Old 11-12-2010, 05:58 PM Thread Starter
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Well, I went to the dealer today. They had one of their best troubleshooting mechanics check it out but an hour and half later, he said the car is in perfect condition and there were no problems at all! Then the service advisor simply said to use better gas from Shell or BP that burns more slowly than others like Citgo or Marathon, which was what I was using. He also recommended next time I come back to have the fuel injectors cleaned and the fuel filter replaced.
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post #15 of 28 (permalink) Old 11-13-2010, 01:28 AM
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thats pretty bad for highway and city. maybe lots of uphill driving and or lead foot? i get no less the 16 all city and on occation i have urges to rev pass 4000 rpm. i think you should look into possible mantenience such as air filter, gas tank treatment and seafoam.

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