Regular Fuel

[lexus114]

Hello every one on LOC! I know this subject has been beat to death.My question is,when using regular unleaded fuel in the RX,and it adjust`s to run on it.Is their any real adverse affect on the motor OTHER THAN loosing performance/gas millage?? I mean does it really prematurely knock out the A/F sensors,or do any other long term destruction??

[rx350guy]

The owners manual for my 08 RX 350 says to use premium unleaded fuel only, so that's what I do. I don't want to take any chances with the engine just to save a few pennies per gallon by using regular fuel..

Just my .02 cents..

[pauljcl]

The owners manual for my 08 RX 350 says to use premium unleaded fuel only, so that's what I do. I don't want to take any chances with the engine just to save a few pennies per gallon by using regular fuel..

Just my .02 cents..

Yes, my manual says to use 91 octane, which is average of mid-level (89) and hi-level (91 premium)... so, every so often, I put in a 1/2 tank of mid-level. Works fine. Sorry: mistake: Hi-level premium is 93 octane, so 91 is the avge of mid-level and hi-level.

[denslexusgx470]

The 06-newer RX with the updated 350 engine REQUIRE premium 91 fuel. The RX330 and older RX300s only RECOMMEND 91 premium unless you are experiencing a ping with your engine...

It's a case to case scenario. Some cars that do not necessarily need 91 pings like hell with 87 served. My 4Runner does not require 91 but it's pinging with the 87 I'm putting in

[SmilingBoognish]

The way your ECU adjusts for lower octane fuel is by sensing detonation due to the fuel air mixture igniting in your cylinder before it is supposed to do so. Detonation is harmful to your engine, but the question is how quickly does your ECU pull timing to account for the lower octane fuel. I usually run premium (91 here in CA) in our vehicle for peace of mind, but I really think it's silly that Lexus doesn't use the same ECU map as Toyota for the 87 octane stuff.

[Messerchmidt]

Using shell octane 87 (been doing so since new) - no problems

same motor as the camry v6,etc - only the higher compression variants such as in the is350/gs350 need higher octane

[mdrx350md]

you'll be losing mpg with 87 octane so the money you're saving won't be that substantial in addition to possible "damage" you could be doing to your car. my gf runs regular in her 06 TL and the way the car feels with 87 and 93 is night and day. It's just not worth it. If you're able, do your own oil changes and the money saved there can go towards your "premium fuel fund" The cost of conventional oil and genuine toyota filter runs $19.

[jondoe888]

I've used regular in my 07 rx since the dealer's tank ran out - just like the Car Talk guys recommend. I think the slight ignition retarding would hardly effect mileage, power or longevity. And I've never noticed any pinging on hills or heavy acceleration, but we rarely stress the engine in our advanced age.

And octane is ONLY about pinging. Premium isn't cleaner or better - but it is more expensive. Occasional mild pinging won't damage an engine, and the computer adjusts the timing to the octane to prevent pinging.

There were some good points brought up. Does anybody REALLY know the answers? I used to be a mechanic, and am just going by judgment.

[BadBrad]

The real answer???

Here is the Lexus propaganda straight out of the manufacturer's sales paperwork foot notes from 2006 and 2010, footnotes 1 and 25, respectively.

"Ratings achieved using the required premium unleaded gasoliune with an octane rating of 91 or higher. If premium fuel is not used performance will decrease." When they say "required" they meant required to squeeze that last four horsepower out of the engine.

I've only run 87 octane for 34,000 miles in the '06 and drive the thing harder than most folks do 'cuz I'm a lead foot. Never a problem with 87 octane. No pinging, no pre-ignition, no detonation. Run 91 octane if you like throwing money away. Higher octane only delays the onset of the knock sensor telling the computer to take two degrees of ignition lead out of the advance curve, and then only on a really hot day. Most of you guys will never feel the difference.

[Claude7629]

How about racing fuel? I have found 100 octane and was curious about using it. It is called racing fuel at the stations where I have seen it.

[lexus114]

The real answer???

Here is the Lexus propaganda straight out of the manufacturer's sales paperwork foot notes from 2006 and 2010, footnotes 1 and 25, respectively.

"Ratings achieved using the required premium unleaded gasoliune with an octane rating of 91 or higher. If premium fuel is not used performance will decrease." When they say "required" they meant required to squeeze that last four horsepower out of the engine.

I've only run 87 octane for 34,000 miles in the '06 and drive the thing harder than most folks do 'cuz I'm a lead foot. Never a problem with 87 octane. No pinging, no pre-ignition, no detonation. Run 91 octane if you like throwing money away. Higher octane only delays the onset of the knock sensor telling the computer to take two degrees of ignition lead out of the advance curve, and then only on a really hot day. Most of you guys will never feel the difference.

The way it feels on regular,I think it retards the timing more than 2 degrees. Feels more like 3 or 4 Degrees.

[lexus114]

The way your ECU adjusts for lower octane fuel is by sensing detonation due to the fuel air mixture igniting in your cylinder before it is supposed to do so. Detonation is harmful to your engine, but the question is how quickly does your ECU pull timing to account for the lower octane fuel. I usually run premium (91 here in CA) in our vehicle for peace of mind, but I really think it's silly that Lexus doesn't use the same ECU map as Toyota for the 87 octane stuff.

"I really think it's silly that Lexus doesn't use the same ECU map as Toyota for the 87 octane stuff." BINGO!! Theirs`s the answer right their! Lexus maps the ecm for premium!

[rx350guy]

How about racing fuel? I have found 100 octane and was curious about using it. It is called racing fuel at the stations where I have seen it.

I believe the way it reads is '91 octane or higher', so I can't see why 100 octane wouldn't be fine. But I don't know if you'd be getting any better performance out of the more expensive fuel..

[Claude7629]

How about racing fuel? I have found 100 octane and was curious about using it. It is called racing fuel at the stations where I have seen it.

I believe the way it reads is '91 octane or higher', so I can't see why 100 octane wouldn't be fine. But I don't know if you'd be getting any better performance out of the more expensive fuel..

I am almost empty so I'm going to try a couple of gallons. If things don't sound good I will fill up with 93 octane to dilute the 100. Let you know how thing go.

[Chris Parker]

Hello every one on LOC! I know this subject has been beat to death.My question is,when using regular unleaded fuel in the RX,and it adjust`s to run on it.Is their any real adverse affect on the motor OTHER THAN loosing performance/gas millage?? I mean does it really prematurely knock out the A/F sensors,or do any other long term destruction??

The car needs 91 octane. You can mix equal amounts of 89 and 93, or 1/3 of 87 and 2/3 of 93 to obtain the required 91 octane. Always put the 93 in first so you don't add too much 89 or 87. Usually mixing 87 and 93 yields a better net price per gallon than 89 and 93, not sure why that is.

[cduluk]

I do see a night and day difference between running a full tank of 87 vs a full tank of 91/93.

I've noticed this in my 03 rx300, in the rx400h and am currently noticing it in my cousin's 00 toyota camry 4cyl.

I've had my cousin's 2000 toyota camry 4cyl for the past couple of weeks. She gave it to me with 87 (she uses the cheap stuff) and i noticed it seemed to struggle when you hit the accelerator, and it seemed to take FOREVER to redline; didn't feel right. When the tank ran out, i filled it with either 91 or 93 from shell or Sonoco. Since then, i've notice a HUGE increase in performance. I swear, if the accelerator is hit the right way, the camry seems to have almost as much power as the Rx300 did (maybe a bit of an exaggeration, but you get my point). With the better fuel, the camry seems to shift more regularly and have smoother transitions.

Maybe i feel so much of a difference because it's a 4cyl toyota, but still, it's a BIG difference. I don't think using 91/93 in a camry can hurt, but i like the difference and the car seems to react better as well.

[SmilingBoognish]

I do see a night and day difference between running a full tank of 87 vs a full tank of 91/93.

I've noticed this in my 03 rx300, in the rx400h and am currently noticing it in my cousin's 00 toyota camry 4cyl.

I've had my cousin's 2000 toyota camry 4cyl for the past couple of weeks. She gave it to me with 87 (she uses the cheap stuff) and i noticed it seemed to struggle when you hit the accelerator, and it seemed to take FOREVER to redline; didn't feel right. When the tank ran out, i filled it with either 91 or 93 from shell or Sonoco. Since then, i've notice a HUGE increase in performance. I swear, if the accelerator is hit the right way, the camry seems to have almost as much power as the Rx300 did (maybe a bit of an exaggeration, but you get my point). With the better fuel, the camry seems to shift more regularly and have smoother transitions.

Maybe i feel so much of a difference because it's a 4cyl toyota, but still, it's a BIG difference. I don't think using 91/93 in a camry can hurt, but i like the difference and the car seems to react better as well.

It's psychosomatic. Higher octane will give no increase in performance for a vehicle designed to run on 87. In a modern car that was designed to run on 91 that has retarded timing after sensing engine knock will give back the performance very incrementally, and there will absolutely not be a "night and day" difference.

[cduluk]

Trust me, the difference is VERY clear on the camry.

[SmilingBoognish]

Trust me, the difference is VERY clear on the camry.

I'd trust a dyno plots, not your butt dyno. :P

[EDHills Joe]

:)

Hello every one on LOC! I know this subject has been beat to death.My question is,when using regular unleaded fuel in the RX,and it adjust`s to run on it.Is their any real adverse affect on the motor OTHER THAN loosing performance/gas millage?? I mean does it really prematurely knock out the A/F sensors,or do any other long term destruction??

We've been using regular since April '06 in the '07 RX350 with no adverse effects. The mileage usually is around the mfr's estimate overall.

Vehicle is driven in Northern Cal. in the foothills.

EDHills Joe

[Chris Parker]

Trust me, the difference is VERY clear on the camry.

I'd trust a dyno plots, not your butt dyno. :P

His Camry could have carbon buildup inside the engine causing higher compression in one or more of the cylinders, and therefore the higher octane fuel is really what his car needs to avoid engine knock and run correctly under those conditions.

[cduluk]

Trust me, the difference is VERY clear on the camry.

I'd trust a dyno plots, not your butt dyno. :P

His Camry could have carbon buildup inside the engine causing higher compression in one or more of the cylinders, and therefore the higher octane fuel is really what his car needs to avoid engine knock and run correctly under those conditions.

could be- the thing was never really taken care of.

It really was night and day between the 87 and 93.