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
#7 of 16 Re: Fuel for the RX 350 [911flygirl]
Sep 14, 2010 (9:00 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 16 Re: Fuel for the RX 350 [maximafan]
Sep 15, 2010 (8:34 am)
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 16 Re: Fuel for the RX 350 [smarty666]
Sep 17, 2010 (7:31 pm)
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 16 Re: Fuel for the RX 350 [maximafan]
Sep 18, 2010 (10:50 am)
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 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?