Last post on Sep 10, 2013 at 10:51 AM
You are in the Lexus RX 300/330/350
What is this discussion about?
Lexus RX 350, Fuel System, SUV
#11 of 16 Re: Fuel for the RX 350 [smarty666]
Sep 21, 2010 (1:08 pm)
"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 16 Re: Fuel for the RX 350 [wwest]
Sep 21, 2010 (1:13 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 16 Noise Under Car
May 11, 2012 (4:58 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 16 Re: Noise Under Car [randy114]
May 12, 2012 (5:01 am)
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 16 Re: Noise Under Car [kwbuggy]
May 13, 2012 (6:23 pm)
Thanks! I was worried that it might run the battery down.
#16 of 16 Re: Fuel for the RX 350 [smarty666]
Sep 10, 2013 (10:51 am)
I have a 2010RX 350 and never noticed any difference putting regular or premium fuel and did numerous MPG test - no difference. Performance no difference. And to the point of voiding a warranty how would anyone be able to determine. My service advisor told me she has a 350 and uses regular gas and she talks with certified service techs everyday. Here some math. I drive 25000 miles a year
25000/22 mpg= 1136 gallons per year x 5 years = 5681 gallons
5681 gallons times .35 gallon= $1988 savings. That's worth thinking about especially since there is no improvement on gas mileage or decrease performance. Consumer reports advises the difference between high octane gas "recommend vs required" such as a turbo engine. Just saying if there is no clear advantage why spend the money?