What fuel grade are you using in your RX350?
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GrizzlyMan (09-13-22)
09-19-22, 07:33 AM
#409
It will get better as the engine breaks in. Just did a 250 mile road trip mostly on interstate type roads with minor changes in elevation got 26.2 running at 78 on the Interstate mostly. Run 65 and you'll likely get close to or somewhat over 27.0 on 87. Absolutely no performance issues even on ECO mode there is plenty of pep.Out 2022 RX350 FWD has a little over 8K miles on it...
12-11-23, 07:33 AM
#410
Interesting info on everyone's mpg experience. It doesn't seem like the RX350 is that bad considering it's an SUV, has some weight to it, and it's a V6. We are currently in the market for a 2021 or 2022 and both commute 34 miles to work (95% of it is highway). So if it can get mid to higher 20's we'll be very happy. As far as best fuel regarding 87 vs 93 octane, you're going to be better off with 93 octane. People try to point out 93 is pointless, that Lexus designed it to run on 87 octane...well actually Lexus designed it to run on 93 octane. If you look at the rated power they advertise, that's rated on 93 octane. More importantly you have an 11.8:1 compression ratio and a direct injection engine that would benefit from 93. Yes it's 'designed' to also run on 87 octane, but that design is more of a patch. It will pull the timing to avoid knock but that doesn't mean it's ideal, and over the long term you could have more carbon build up. Similar to how say a Mustang or Corvette may have premium recommended, but can run on 87 octane. It absolutely can, but it's not ideal. I don't think 93 octane is a waste on an 11.8:1 compression ratio engine. Direct injection is also known for more carbon build up, and 93 octane has more additives to fight that build up. The Lexus/Toyota does have port injection to help with this too but better fuel helps immensely. If you plan on keeping your car for the long term it's probably a good idea to put 93 octane. Here is a great vid on fuel.
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jollick (12-12-23)
12-11-23, 11:25 AM
#411
Lexus Test Driver
Thread Starter
Presuming a $1 diff per gallon and over the course of 100K miles getting roughly 20MPG, you'll spend an additional $5,000 on premium. Highly doubt that will be worth it.
12-11-23, 12:08 PM
#413
That’s probably a fairly accurate estimate, but for me it’s worth it. It’s more to do with it being a higher compression and direct injection motor which really should have a higher octane fuel. Not too long ago you could never get away with 87 on 11.8:1, but software has really changed that game, but it’s still not ideal. You are much more prone to carbon build up with 87. If you are leasing or only keeping it 3-5 years it won’t matter. I keep my vehicles roughly 10 years and about 200k miles and it could end up costing more in maintenance over that long term. I also don’t mind paying more for a certain oil brand (amsoil) even though the argument can be made any decent oil will work…or oil changes can be 10k miles but I won’t go past 5k. Same with the fueling. I’ve had very decent luck with my vehicles lasting (except my only Ford of course) and I think these little things add up over the long run. I’ve had vehicles that required premium before as well so it doesn’t bother me too much to use it now…although I imagine if they had today’s software they would probably be able to run 87. Alright my 2 cents and to each their own.
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ravenuer (12-11-23)
12-12-23, 06:04 AM
#415
That’s probably a fairly accurate estimate, but for me it’s worth it. It’s more to do with it being a higher compression and direct injection motor which really should have a higher octane fuel. Not too long ago you could never get away with 87 on 11.8:1, but software has really changed that game, but it’s still not ideal. You are much more prone to carbon build up with 87. If you are leasing or only keeping it 3-5 years it won’t matter. I keep my vehicles roughly 10 years and about 200k miles and it could end up costing more in maintenance over that long term. I also don’t mind paying more for a certain oil brand (amsoil) even though the argument can be made any decent oil will work…or oil changes can be 10k miles but I won’t go past 5k. Same with the fueling. I’ve had very decent luck with my vehicles lasting (except my only Ford of course) and I think these little things add up over the long run. I’ve had vehicles that required premium before as well so it doesn’t bother me too much to use it now…although I imagine if they had today’s software they would probably be able to run 87. Alright my 2 cents and to each their own.
12-13-23, 05:48 PM
#416
Driver School Candidate
Typically on my 2017 4RX, I fill it up with 91 octane (premium). Today though, I decided to give 93 octane (ultra) a try. Upon a quick observation, I noticed my RX seems slightly happier and more responsive being pumped with 93 octane so I probably will change it's diet. (If only 93 octane was more common on gas pumps in my area)
12-14-23, 02:36 AM
#417
It all makes sense when looked at from a marketing and engineering perspective. The higher compression engine is more efficient and thus has more power and gets better gas mileage. This is a good thing but requires higher octane gas. A car that requires the more expensive 93 octane is not exactly a good selling point. The engineers at Lexus had to come up with a design/configuration that would make the use of 87 octane acceptable (and they did). Now everybody is happy. They will sell many more cars now because the lower octane gas makes the vehicle less expensive to own.
I have not tried 93 octane yet in my RX but will do it sometime just to see if I notice a difference. I say use whatever you like. The owners manual says "Select octane rating 87 or higher" and that says it all.
I have not tried 93 octane yet in my RX but will do it sometime just to see if I notice a difference. I say use whatever you like. The owners manual says "Select octane rating 87 or higher" and that says it all.
Last edited by jcg0324; 12-14-23 at 03:14 AM.
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TRDOffroad (12-14-23)
12-14-23, 02:54 AM
#418
I don't see that being the definitive answer, however, because they also designed a crafty VVT-iW system to put on this engine, which lowers the compression as needed to avoid spark knock under load and acceleration when it's burning 87 octane fuel: https://en.wikipedia.org/wiki/VVT-i
So I see the correct understanding of our engine design as being "Originally designed to perform optimally on 91 octane and subsequently modified to perform satisfactorily with any fuel in the 87-93 octane range." I assume the Lexus marketing department was the major impetus for the VVT-iW modification. "It runs on regular," were the first words out of the salesman's mouth when I first stepped into the dealer's show room in 2014 and saw the 2015 models.
Personally, being more motivated by optimal performance than the economics of it, I use Shell 89 octane and find it noticeably smoother than the 87. I occasionally end up at Costco getting their 93 octane but I can't detect any difference between that and the 89 from Shell. I've seen 27 mpg on a long trip on midwest freeways, but I'm lucky if I hit 21 in my daily suburban driving -- usually closer to 19.
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12-14-23, 11:16 AM
#419
Agree 100%. Used regular when premium was required for many vehicles for almost a million miles of driving. Have never had one issue and also never noticed any increase in gas mileage. The little bit of loss in performance, I could care less. It is a Lexus not a Porsche. This topic will be debated over and over with passion. Does it make you feel good as a purchaser that the car requires premium, the best gas. When later you are at the pump and the difference is $.70 a gallon do you still feel good using it again IMO with no difference. Don't believe here are so experts. If it makes you feel better spend the extra $$$.
I always revert back to two MIT graduates that are car mechanics who had a syndicated radio show called Car Talk for 35 years.
http://www.cartalk.com/content/premi...egular-0#myth4
From the USA Today:
The only modern engines that should really need premium are those with superchargers, which force-feed fuel into the cylinders. "You're driving along and just tramp the gas and the knock sensor cannot sense the knock fast enough in some cases," because the supercharger boosts pressure so fast, says Bob Furey, chemist and fuels specialist at General Motors.
Burning regular when the owner's manual specifies premium won't void the warranty, nor damage the engine, even the most finicky automakers say. "You're giving up perhaps just a little bit of performance that a customer wouldn't really even notice, it's so slight," says Furey.
I always revert back to two MIT graduates that are car mechanics who had a syndicated radio show called Car Talk for 35 years.
http://www.cartalk.com/content/premi...egular-0#myth4
From the USA Today:
The only modern engines that should really need premium are those with superchargers, which force-feed fuel into the cylinders. "You're driving along and just tramp the gas and the knock sensor cannot sense the knock fast enough in some cases," because the supercharger boosts pressure so fast, says Bob Furey, chemist and fuels specialist at General Motors.
Burning regular when the owner's manual specifies premium won't void the warranty, nor damage the engine, even the most finicky automakers say. "You're giving up perhaps just a little bit of performance that a customer wouldn't really even notice, it's so slight," says Furey.
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Freds430 (12-27-23)
12-15-23, 05:50 PM
#420
Wow, waking up the octane thread again.
I will add this comment about naturally aspirated cars octane requirements. Chevy, Ford, and Dodge v8's require premium if you want it to run as designed to. My Chevy SS will slap me in the face if I choke her with Regular gas.
I will add this comment about naturally aspirated cars octane requirements. Chevy, Ford, and Dodge v8's require premium if you want it to run as designed to. My Chevy SS will slap me in the face if I choke her with Regular gas.
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TRDOffroad (12-18-23)