- #178 of 260
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Re: 2010 RX [mickey34]
by wwest
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Apr 16, 2009 (8:24 am)
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Replying to: mickey34 (Apr 15, 2009 10:02 pm)
When we picked up our '01 911 C4 at the factory in Gernany I was told that I would not always be able to find the recommended premium fuel during our suceeding travels throughout europe and fueling with regular would be fine. I was cautioned that I should NEVER use leaded fuel since they would then have to replace the catalysts ($1000) prior to shipment to the US.
When I inquired of the details I was told that the engine used the more sensitive new non-resonant knock sensors and if even any small level of knock/ping was detected for which timing adjustment could not be done EFI would be used to enrich the mixture.
Apparently with EFI and the new knock sensors a high compression engine that would normally require premium only can run safely on regular provided the mixture is enriched beyond the point of dieseling due to compression.
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- #179 of 260
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Re: 2010 RX [rparis]
by md_outback
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Apr 16, 2009 (9:23 am)
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Replying to: rparis (Apr 15, 2009 3:00 pm)
A better question to ask is why does Lexus recommend premium fuel when Toyota recommends regular fuel for what is basically the same engine. The only difference I can see is that the Lexus RX350 (prior to 2010 model) was rated at 270 hp and 251 lb-ft of torque using premium, whereas most of the Toyota applications of the same engine in Venza, Camry, Avalon and RAV4 are rated at 268 hp and 248 lb-ft using regular (actually RAV4 has 269 hp). Maybe the Lexus has better airflow or some other improved technological advantage. OR, maybe the premium fuel designation allows Lexus to claim the extra few hp and maybe even inches it into one more mpg based on the EPA rules to give it a competitive edge. All I can personally report is that based upon 34,000 miles and 1700 gallons and about 120 fill-ups, I did not see any real difference, so I continue to use regular grade in my '07 RX350. These days that works out to about $4.50 a week, or $234 per year - and that's like getting several free rounds of golf!
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- #180 of 260
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Re: 2010 RX [md_outback]
by wwest
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Apr 16, 2009 (9:59 am)
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Replying to: md_outback (Apr 16, 2009 9:23 am)
Lexus, UPSCALE, can recommend premium with impunity, pretty much. Whereas Toyota....
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- #181 of 260
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Regular Fuel is OK...
by sideways3
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Apr 18, 2009 (11:58 am)
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Just picked up my new 2010 RX...was told regular is perfectly ok and will have no impact on performance.
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- #182 of 260
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Re: Regular Fuel is OK... [sideways3]
by rparis
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Apr 18, 2009 (1:31 pm)
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Replying to: sideways3 (Apr 18, 2009 11:58 am)
Thanks -let us know and let us know your thoughts on the vehicle in a few days. I am planning on buying one after driving a 2001 with over 100k miles.
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- #183 of 260
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Re: Regular Fuel is OK... [sideways3]
by mickey34
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Apr 19, 2009 (10:03 am)
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Replying to: sideways3 (Apr 18, 2009 11:58 am)
Hi Sideways3. I bought my 2010 last month and went in for the 1000 mile checkup and asked my service advisor whom I know very well about the gas to use, He suggests using the premium for the first 5000 miiles then maybe using the 89 octane. From what I got out of it the engine has some changes. I know it is only five more hp but if you read up about it the torque is at a lower Rpm! By the way the tires had 36 psi I lowered to 32 psi and made a noticeable ride difference I do have AWD so it feels a little heavier, I think I got lucky as I got all the major packages and color I wanted I had to wait and extra three weeks as it was on the way from Japan. It was worth the wait. Mickey
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- #184 of 260
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Re: Regular Fuel is OK... [mickey34]
by la4mead
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Apr 19, 2009 (10:30 am)
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Replying to: mickey34 (Apr 19, 2009 10:03 am)
When the engine management system adjusts for lower octane (87 instead of 91) the difference may or may not be noticeable to you, depending on how you drive, weather, terrain, etc. Like many modern vehicles designed to run on premium (but those not requiring it) the RX is able to adjust (via knock sensor) to avoid "ping" so get by with what you can.
So if you're driving in hot weather (when higher octane is most usable), climbing steep grades, full load, etc. you may want to use premium to avoid the resulting retarded engine timing, which ultimately will affect performance and fuel economy to some (possibly not noticeable) degree.
It shouldn't hurt the RX to run on 87 octane, though. Just performance. Especially if you drive moderately on flat terrain in cool weather.
P.S. Lowering the tire pressure will make the ride softer and more dampened, definately at the expense of handling sharpness (on pavement) and fuel economy. I run at or near the max suggested on tire sidewall to maximize handling, fuel economy and tire life. But the ride does get "stiffer" which I don't mind.
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- #185 of 260
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Re: Regular Fuel is OK... [la4mead]
by wwest
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Apr 19, 2009 (11:46 am)
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Replying to: la4mead (Apr 19, 2009 10:30 am)
"..use premium to avoid the resulting retarded engine timing..."
Probably not....
In modern day vehicles, at least for the last 5-8 years, spark knock is often NOT the problem, so retarding the ignition is rarely the solution. The engine/transaxle ECU is capable, using the crank position sensor, to tell if the detected knock/ping ocurring prior to ignition is due to low octane fuel. For low octane fuel the solution is slight enrichment of the mixture under knock/ping conditions, high throttle openings.
For knock/ping due to engine lugging a simple downshift is used. If there is no downshift available then DBW will be used to dethrottle the engine and prevent damage.
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- #186 of 260
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Re: Regular Fuel is OK... [la4mead]
by mickey34
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Apr 19, 2009 (12:19 pm)
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Replying to: la4mead (Apr 19, 2009 10:30 am)
Thanks for your helpfull information. Maybe I will split the difference on the tire preasure Mickey.
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- #187 of 260
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Re: Regular Fuel is OK... [wwest]
by mickey34
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Apr 19, 2009 (12:21 pm)
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Replying to: wwest (Apr 19, 2009 11:46 am)
Thanks for the Info
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