Low Mpg. Would Appreciate Suggestions.

[trips1]

I was going through the forum and find that people are getting 17-20mpg in city!!

I have a lexus RX300, 2001, 89500 miles and am getting 15mpg in city and around 19-20mpg on freeways.

I got a 90K mile service done (without timing belt change) along with transmission flush at 88000 at a Toyota dealer.

I did not get the spark plugs changed.

It has been through the oil sludging problem at 70K when Lexus changed "some" part of the engine as part of the warranty.

I have average driving habits and drive in california i.e. in a moderate weather.

- So i am just wondering why my mpg is so low. It used to by 17mpg but has gone down to 15mpg now :-(

- And if i want to take it to a Toyota service center or any independent mechanic what should i ask them to check?

- Or is it advisable to take it to Lexus Service Center (though they are gonna suck money)

Can there be an issue with the Oxygen Sensor. How and where can i get it checked if needed.

Can there be an issue with the spark plugs? Again how do i find out that.

Anything else that can be wrong? I don't want to go to a dealer or independent mechanic and ask them to investigate and then let them throw tons of improvements that may not be necessary at all........

Thanks a lot in advance.

[Grumpa72]

If you suspect that your spark plugs are worn, by all means, replace them. I think a search of this board will show you that the front plugs are pretty straight forward while the rear ones can be a PITA. If your oxygen sensor was bad, or any other sensor for that matter, it should throw a code and you would have a Check Engine light. I don't have my manual in front of me but it will tell you what the change interval is for plugs. You can have a shop evalute your exhaust to see if your catalytic converter is malfunctioning, although that is highly unlikely with 89500 miles.

Traffic and speed can make the biggest difference in mileage, as you know. How heavy is traffic and how fast do you drive? Has the mileage dropped significantly recently?

There really isn't much that a mechanic can do to our cars anymore that falls under the category of a tuneup. I still have a classic with points, plugs, wires and a distributor. This car still needs timing, dwell, and carb tuneups but, then again, it is 37 years old!

[lenore]

If you have AWD your mileage is not too far off. I suggest cleaning the MAF sensor, changing the oil to a full synthetic like Mobil 1 5-20w, change your air filter, check your tire pressure and run 33lbs pressure. Put some Chevron Techron fuel cleaner in the gas tank and then see what you get. The California Gas sucks bigtime, The summer blend may be in the channel which might give poorer performance. As for your spark plugs they are probably fine. I changed mine at 120k miles and they looked great, new ones made no change to gas mileage.

[trips1]

If you have AWD your mileage is not too far off. I suggest cleaning the MAF sensor, changing the oil to a full synthetic like Mobil 1 5-20w, change your air filter, check your tire pressure and run 33lbs pressure. Put some Chevron Techron fuel cleaner in the gas tank and then see what you get. The California Gas sucks bigtime, The summer blend may be in the channel which might give poorer performance. As for your spark plugs they are probably fine. I changed mine at 120k miles and they looked great, new ones made no change to gas mileage.

Thanks for the info.

I have a 2WD. With sky rocketing gas prices 15mpg sucks!!!!! :-)

[Randy&Bonnie]

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[code58]

If you have AWD your mileage is not too far off. I suggest cleaning the MAF sensor, changing the oil to a full synthetic like Mobil 1 5-20w, change your air filter, check your tire pressure and run 33lbs pressure. Put some Chevron Techron fuel cleaner in the gas tank and then see what you get. The California Gas sucks bigtime, The summer blend may be in the channel which might give poorer performance. As for your spark plugs they are probably fine. I changed mine at 120k miles and they looked great, new ones made no change to gas mileage.

I agree with Lenore on every point- Those things might just make the difference. The people that tell you that are getting incredible mileage on an RX would lie about other things too. :D :D :D Seriously, those suggestions are the BEST place to start. :)

[pauljcl]

If you have AWD your mileage is not too far off. I suggest cleaning the MAF sensor, changing the oil to a full synthetic like Mobil 1 5-20w, change your air filter, check your tire pressure and run 33lbs pressure. Put some Chevron Techron fuel cleaner in the gas tank and then see what you get. The California Gas sucks bigtime, The summer blend may be in the channel which might give poorer performance. As for your spark plugs they are probably fine. I changed mine at 120k miles and they looked great, new ones made no change to gas mileage.

I agree 100% with the above. I have a '99 RX300 AWD 66K miles, and we get - (90% city driving) 15.9 mpg indicated. We often run the A/C. We use Mobil 1 5-30W, have done the full 60K maintenance (but got suckered by the dealer who swore that the timing belt change was necessary at 60K miles in hotter climes), and run the tires at 33-34lbs. Another factor may be the use of ethanol, which is slowly being mandated across the country. Ethanol gives some 30% lower energy=>mileage, which corresponds (at 10% ethanol content) to a 3% decline in mileage, i.e. from 16mpg to 15.6mpg approx. On the highway, we travel at 70mph or slightly more usually (in line with traffic here in Miami), but in the city we accelerate slowly and are parsimonious in our braking.