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Discussion Starter #1
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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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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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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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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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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Discussion Starter #9
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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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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Discussion Starter #14
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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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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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.
The fuel filter is integrated into the fuel pump and is not a part that is normally changed or serviced. If he's thinking it's a normal service part you swap in 10 minutes like an old Chevy or something you might want to find a more competent mechanic.

Picture of the "filter" here:
http://www.clublexus.com/forums/attachments/is-second-generation/110958d1189095509-no-fuel-filter-in-a-is-250-isx50-subtank-system.jpg

They're fulla crap on the "use better gas" thing too unless you go to one specific station all the time that has cracked storage tanks with water leaking in or something.

First thing I'd suggest though since you haven't had the car but a month and haven't driven it much-

Run the tank quite low on gas, then fill up with "good" gas just to shut that idea up... now take a long trip. All highway if possible, at least 300-400 miles.

If your mileage is in the high 20s (like 26-28) then the car is probably ok and there's something weird about the way you're driving it or something.

If you're still seeing 15 mpg or similarly poor mileage then I'd contact Lexus corporate and explain you own a Lexus, still under warranty, that is getting about half of the mileage it should, and your local dealer has been unable to find the source of the issue, and see what they say.
 

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The fuel filter is integrated into the fuel pump and is not a part that is normally changed or serviced. If he's thinking it's a normal service part you swap in 10 minutes like an old Chevy or something you might want to find a more competent mechanic.

Picture of the "filter" here:
http://www.clublexus.com/forums/attachments/is-second-generation/110958d1189095509-no-fuel-filter-in-a-is-250-isx50-subtank-system.jpg

They're fulla crap on the "use better gas" thing too unless you go to one specific station all the time that has cracked storage tanks with water leaking in or something.

First thing I'd suggest though since you haven't had the car but a month and haven't driven it much-

Run the tank quite low on gas, then fill up with "good" gas just to shut that idea up... now take a long trip. All highway if possible, at least 300-400 miles.

If your mileage is in the high 20s (like 26-28) then the car is probably ok and there's something weird about the way you're driving it or something.

If you're still seeing 15 mpg or similarly poor mileage then I'd contact Lexus corporate and explain you own a Lexus, still under warranty, that is getting about half of the mileage it should, and your local dealer has been unable to find the source of the issue, and see what they say.
Spot on.

Dude, I'm an automotive dunce and that "good gas" explanation is such horse shit, I would have laughed in his face.

Other than that, I'd do exactly what Knightshade wrote.
 

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Discussion Starter #18
The service advisor at McGrath Lexus in Chicago, which is where I went, talked to me about gasoline mixtures. He said that fuels from Shell and BP have different mixtures that cause them to burn slower and stuff like that. I came home and did research and found out that is sort of true but will only get me maybe 1-2 MPG more. Again, the actual mechanic who worked on my car said there's no leaks in the fuel delivery, exhaust, or any of that. The tire pressure is correct and the car is caught up with maintenance.

Knightshade, it looks like you know a lot about this car. I was changing the oil two weeks ago and after draining out all the oil, I tried to take off the oil filter housing but that thing was stuck on like crazy. I'm guessing the last owner of the car went to Jiffy Lube or something like that because Lexus has no records of oil changes for this car. Could an over-tightened oil filter cause any problems? Last thing, I want to change the spark plugs next month. Is it okay to change them outside in my garage when it's like 20 degrees out and do I have to change all of them at once?
 

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The service advisor at McGrath Lexus in Chicago, which is where I went, talked to me about gasoline mixtures. He said that fuels from Shell and BP have different mixtures that cause them to burn slower and stuff like that. I came home and did research and found out that is sort of true but will only get me maybe 1-2 MPG more. Again, the actual mechanic who worked on my car said there's no leaks in the fuel delivery, exhaust, or any of that. The tire pressure is correct and the car is caught up with maintenance.

Knightshade, it looks like you know a lot about this car. I was changing the oil two weeks ago and after draining out all the oil, I tried to take off the oil filter housing but that thing was stuck on like crazy. I'm guessing the last owner of the car went to Jiffy Lube or something like that because Lexus has no records of oil changes for this car. Could an over-tightened oil filter cause any problems? Last thing, I want to change the spark plugs next month. Is it okay to change them outside in my garage when it's like 20 degrees out and do I have to change all of them at once?

Overtightened filter housing wouldn't be much of an issue other than making it hard to remove... beyond that long as there's no leaks it's only a problem for when you need to take it off. Be aware there's a special toyota/lexus tool to remove the filter that's stupid expensive compared to a $5 oil filter wrench... some folks have reported it's near impossible to change without this tool, some have gotten by fine on the cheapo one. YMMV.


On the plugs, I'd certainly prefer to change them all at once, to insure you're "testing" against a complete fresh set and have consistent results.

Changing in the cold shouldn't be a problem beyond the fact your hands will get numb which might make things difficult... the car is gonna be off/cold anyway, and nothing you're working with parts-wise should get dangerously brittle "indoors" in a garage with an outdoor temp of 20.


And BTW, seriously, apart from marketing stuff, "brand" of gas won't impact mileage.

if any brand of gas could proveable provide a 1-2 mpg increase over other brands they'd be running commericals every 30 seconds telling you that.

Instead they'll make claims like "No other brand offers better performance/mileage"

Which is true.

Equally true is other brands don't offer WORSE performance/mileage either, generally speaking.


Because with very little exception (some detergent quantities above the federally required minimum) gasoline is gasoline. 93 octane is 93 octane.

You will find anecdotal stories all over about "X brand works better in my car" and then another guy saying the opposite... but you won't find (to my knowledge) any science or objective evidence one brand of gas offers measurable better mileage or performance than another at equal octane.
 

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15.5 mpg on first tank, premium gas

Hi all, I'm new to the forum, community & Lexus. I have an 08 IS350 with 76K that has always been dealer maintained. Last oil change was around 74K. And the 75K service was done as scheduled. Clean service history from lexus.com

After my first full tank of premium gas and Atlanta city only driving (very little highway), I calculated my actual mileage at 15.5mpg.

I do not have a lead foot.

This seems awfully low for such a well maintained car (despite the high mileage).

I've read this thread and others to check for certain things (air filter, etc), but since all the work has been done at Lexus, I'm presuming that this all as it should be.

Any other ideas?

Thanks for any help. I really like the car, but I can't abide this low fuel economy.
 
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