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2010 Lexus RX 350 Gas Tank.

15 messages,  Last post on May 13, 2012 at 7:23 PM

You are in the Lexus RX 300/330/350 Forum.

What is this discussion about? Lexus RX 350, Fuel System, SUV

Messages Page 2 of 2

#6 of 15 Re: 2010 rx350 gas tank [maximafan] by smarty666

Sep 14, 2010 (5:33 pm)

Replying to: maximafan (Sep 06, 2010 2:07 pm)
First, never use the trip computer or mpg readouts on the vehicle. I have found time after time they are usually not accurate. Still the best and true method is to manually calculate the amount of miles on the trip odometer by the gallons of gas on the pump to the furthest decimal place if possible. Do that for several gas fill-ups and take the avg from at least 5 or more fill-ups and that is about as accurate as you can get.
 
A lot of things go into fuel economy and gas mileage and a lot of factors out of our control, such as temperature, traffic, pump cut offs, etc. Also there are other factors that are under our control, how you drive (lead foot for instance), city vs highway, tire brand/class used on vehicle, tire inflation pressure, suspension issues, drag issues, brand of gasoline used, if the vehicle is loaded down, etc.
 
Just for everyone's questions, the Lexus website says the RX350 comes with a 19.2 gallon gas tank and when I was shopping last year that's what the sales people told me so that is the size your tank should be. If it is not, then there is a big boo boo on your RX! Also, the fuel recommendation is premium gas so that is what should be put in it (91 octane or higher). I've come to find over the years, that when it comes to gasoline whether is says requires or recommends premium I put premium in. Not only did it keep knocking/pinging and engine idle issues at bay but it gives you maximum performance. I would not be putting regular in a RX if I were you. If you wanted to do that then you should have gotten a Toyota.
 
Sometimes you can get away with mid-grade (plus) instead of premium but around where I live, the difference in price between mid-grade and premium is 10 cents so I don't mind spending the extra $1.50 a week putting in premium.

#7 of 15 Re: Fuel for the RX 350 [911flygirl] by maximafan

Sep 14, 2010 (10:00 pm)

Replying to: 911flygirl (Sep 09, 2010 12:00 pm)
With my '07 RX, my service advisor said it was fine to put regular unleaded in the RX. I drove that car for four years just putting regular unleaded with no problems, and I felt that the car got pretty good gas mileage for an SUV. Now I'm driving the 2010 RX, and I'm still putting regular unleaded in it, but I don't believe I'm getting the gas mileage that I was getting in the '07.

#8 of 15 Re: Fuel for the RX 350 [maximafan] by smarty666

Sep 15, 2010 (9:34 am)

Replying to: maximafan (Sep 14, 2010 10:00 pm)
I would say that service advisor is an idiot. It wouldn't be the first time a persona at a stealership has given wrong information. I've had it happen on more than one occasion.
 
Just remember, you only had the RX 4 years under warranty, God knows the long term affect of using regular (6+ years) and once your out of warranty. If something was to ever happen to your exhaust system or anything else related to it out of warranty, it doesn't mean jack squat what that service advisor said to you and you'll be blamed for putting regular in
 
If the owner's manual says premium recommended or required there is a reason for it. You might be able to get away with mid-grade but not with regular. The car is designed for premium.
 
This is just my opinion but I can't understand why you'd spend the money on a expensive luxury vehicle like the RX and then not fill it up with the recommended premium gas. Your not really saving that much money a year by putting the regular in vs the premium just to save a few bucks on a expensive vehicle for everything else (oil, tires, etc).

#9 of 15 Re: Fuel for the RX 350 [smarty666] by maximafan

Sep 17, 2010 (8:31 pm)

Replying to: smarty666 (Sep 15, 2010 9:34 am)
I guess we'll see what happens with the '07, as my sister-in-law is driving it now.
Seriously though, it's not just the service advisor that has suggested this. I've also talked with other auto mechanics regarding using regular unleaded gas vs. premium on vehicles that the manual says otherwise. They've said the same thing.
So, no, I'm not convinced yet about this.

#10 of 15 Re: Fuel for the RX 350 [maximafan] by smarty666

Sep 18, 2010 (11:50 am)

Replying to: maximafan (Sep 17, 2010 8:31 pm)
Well, I can't obviously speak for all vehicles, but I know my 10 Maxima say Premium recommended. I've been putting premium in and its been running great. I live in NJ where we can't pump our own gas. A few months back, the idiot attendant put regular in instead of premium. Before even leaving the station I could tell the difference. The car was idling terribly (steering wheel even vibrating heavily) and the car was struggling to go during acceleration, etc. It was jerking a lot when driving and the mpg went in the toliet. I had to take an easy with the car that entire tank until I could get premium back in.
 
Some guys on a Nissan forum I belong have gotten away with mid-grade with no problems or reduction in mpg but no one is putting in regular. So some vehicles the grade of gas makes a big difference.

#11 of 15 Re: Fuel for the RX 350 [smarty666] by wwest

Sep 21, 2010 (2:08 pm)

Replying to: smarty666 (Sep 15, 2010 9:34 am)
"recommended VS required"
 
IMMHO required means REQUIRED.
 
Recommended means you have the OPTION.
 
For about the past 10 years now "high" compression engines have had the ability to run on regular fuel with no detriment, short or long term. First and foremost the compression ratio is pretty much meaningless except when the cylinder is getting a full A/F mixture charge.
 
So the only times the fuel grade is important is with/at WOT, or close to WOT. The second is engine lugging, operating the engine in a to low gear range for conditions.
 
With the advent of non-resonant, wide band, knock/ping sensors the engine control ECU simply uses the EFI PWM, duty-cycle, to slightly enrich the air/fuel mixture thereby alleviating any tendancy to knock/ping. In the case of lugging the ECU commands a transmission downshift.
 
Slightly lower maximum HP/torque and FE, that's all.

#12 of 15 Re: Fuel for the RX 350 [wwest] by smarty666

Sep 21, 2010 (2:13 pm)

Replying to: wwest (Sep 21, 2010 2:08 pm)
very true but its still a recommendation; they are recommending you put in a certain grade of gas; if you don't follow the recommended octane rating then do not complain about lousy mpg
 
I can tell you from the experience with my 3.5L VQ engine that a high grade displacement engine, such as that one, would have a severe detriment to it if used lower then mid-grade gas so for some engines it still makes a difference. I wouldn't have thought it till I saw and felt how bad the car was struggling to go down the road with regular in it.

#13 of 15 Noise Under Car by randy114

May 11, 2012 (5:58 pm)

My RX350 has a noise that sounds like a small motor running coming from underneath the car at times. The car may have been sitting for hours and when I walk by the car I can hear it running. I can't locate the source but it sounds like it is coming from around the rear of the car by the muffler or the fuel tank. Any ides?

#14 of 15 Re: Noise Under Car [randy114] by kwbuggy

May 12, 2012 (6:01 am)

Replying to: randy114 (May 11, 2012 5:58 pm)
It is just a small fan which purges the vapors from the fuel system. It runs whenever needed. Can be spooky to walk out to your garage after the car has sat for hours and hear it running though.

#15 of 15 Re: Noise Under Car [kwbuggy] by randy114

May 13, 2012 (7:23 pm)

Replying to: kwbuggy (May 12, 2012 6:01 am)
Thanks! I was worried that it might run the battery down.

Messages Page 2 of 2

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