Many Drivers Using Wrong Gas

[lazersharp]

Many dealerships advise people to use regular unlead when purchasing a new car strictly as a selling point when in fact many cars call for premium fuel! When i got 2011 rx 350 the salesman told me to use regular unlead. I thought engine was noisy or i was crazy but went online to see many with same complaint. Investigated my owners manual to find that premium fuel (octane 91 or higher) is strongly recommended and regular unlead (octane 87)will cause knocking noise and engine damage!

My daughter drives an 2008 mazda 3 and manual clearly states that premium fuel is recommended. Switched to premium and car runs smoother...big difference!

everything has a price.

Don't believe everything salesman tells you. Owners manual for 2011 RX clearly says premium fuel, however manual for 2012 RX says Regular recommended.

I do what manual says, put regular gas in my new 2012 RX

[nhrider]

Don't believe everything salesman tells you. Owners manual for 2011 RX clearly says premium fuel, however manual for 2012 RX says Regular recommended.

I do what manual says, put regular gas in my new 2012 RX

I have had 3 RX's. (2004 RX300,2006 RX400H, and 2010 RX350). I ran all on 87 octane ethanol blends. I have had no issues ever, and I put about 80,000 mi on the cars before I replace them. The choice is yours, but that is my experience.

-Dave

[acoldstarnolds79]

Many dealerships advise people to use regular unlead when purchasing a new car strictly as a selling point when in fact many cars call for premium fuel! When i got 2011 rx 350 the salesman told me to use regular unlead. I thought engine was noisy or i was crazy but went online to see many with same complaint. Investigated my owners manual to find that premium fuel (octane 91 or higher) is strongly recommended and regular unlead (octane 87)will cause knocking noise and engine damage!

My daughter drives an 2008 mazda 3 and manual clearly states that premium fuel is recommended. Switched to premium and car runs smoother...big difference!

everything has a price.

No, since the advent of EFI, wide band knock/ping sensors, and monitoring of crank position, the A/F mixture can be slightly enriched if the fuel octane used requires it.

Since about 2000 most "high" compression engines (10:1 EFI, 12:1 DFI) REQUIRE premium ONLY for full, best(?) performance.

I've been running regular here in Houston in my 2008 ES and now in my 2011 Rx since they were both new. No knocking or any noticeable difference from premium. I've tried premium and have to say I cannot tell any difference in power and it makes no difference in MPG.

I've asked at the dealership and been told premium is recommended but the sales guy who told me that said he runs regular in his cars.

[The G Man]

I've been running regular here in Houston in my 2008 ES and now in my 2011 Rx since they were both new. No knocking or any noticeable difference from premium. I've tried premium and have to say I cannot tell any difference in power and it makes no difference in MPG.

I've asked at the dealership and been told premium is recommended but the sales guy who told me that said he runs regular in his cars.

I would stop going to that dealer, they are misinformed. It clearly states that premium is require, not recommanded, in the owner's mannual.

[BadBrad]

The premium fuel "requirement," (the actual words are "required for best performance" and not "required or your warranty is void") is nothing but a marketing ploy to ensure the high priced Lexus makes something like 3.59 more horsepower than the lower priced Toyota pedestrian trash. If you are concerned that you car is slower in the quarter-mile for running 87 octane then lose 30 lbs.

Run 87 all day, all year, and all decade. Your wallet will thank you.

[Alphadog]

I just got a 2010 RX and it runs fine on regular. Had a 2007 for 4 years and it has run on regular the entire time engine is quiet and wife gets 21 mpg - no interstate at all. I don't see how any performance gain would be worth the extra cost for premium. If the engine ever starts knocking or getting noisy i may switch - but I am not worried about engine damage as the modern computers are monitoring for all these conditions.

[jaswood]

Many dealerships advise people to use regular unlead when purchasing a new car strictly as a selling point when in fact many cars call for premium fuel! When i got 2011 rx 350 the salesman told me to use regular unlead. I thought engine was noisy or i was crazy but went online to see many with same complaint. Investigated my owners manual to find that premium fuel (octane 91 or higher) is strongly recommended and regular unlead (octane 87)will cause knocking noise and engine damage!

My daughter drives an 2008 mazda 3 and manual clearly states that premium fuel is recommended. Switched to premium and car runs smoother...big difference!

everything has a price.

No, since the advent of EFI, wide band knock/ping sensors, and monitoring of crank position, the A/F mixture can be slightly enriched if the fuel octane used requires it.

Since about 2000 most "high" compression engines (10:1 EFI, 12:1 DFI) REQUIRE premium ONLY for full, best(?) performance.

I've been running regular here in Houston in my 2008 ES and now in my 2011 Rx since they were both new. No knocking or any noticeable difference from premium. I've tried premium and have to say I cannot tell any difference in power and it makes no difference in MPG.

I've asked at the dealership and been told premium is recommended but the sales guy who told me that said he runs regular in his cars.

"..No knocking or any..."

Human ears are not sensitive enough, or maybe I should say not "quick enough" to discern engine knock when it occurs in these newer EFI engines. The new wideband knock sensors will detect the onset of knock/ping so quickly, and at such a low level, that the driver will never take notice. Upon detection of even these minor levels of knock/ping the ECU will INSTANTLY "detune" the engine. The A/F mixture will be enriched "just enough" to alleviate, abate, the possibility of detonation.

[The G Man]

"..No knocking or any..."

Human ears are not sensitive enough, or maybe I should say not "quick enough" to discern engine knock when it occurs in these newer EFI engines. The new wideband knock sensors will detect the onset of knock/ping so quickly, and at such a low level, that the driver will never take notice. Upon detection of even these minor levels of knock/ping the ECU will INSTANTLY "detune" the engine. The A/F mixture will be enriched "just enough" to alleviate, abate, the possibility of detonation.

And what happens after the engine is detune, it will try to go back to normal until it detects knocking again, then detune again. This cycle happens over and over again, that repeated slight knocking may or may not damage your engine in the long run. I guess I am not willing to take that chance.

[jaswood]

"..No knocking or any..."

Human ears are not sensitive enough, or maybe I should say not "quick enough" to discern engine knock when it occurs in these newer EFI engines. The new wideband knock sensors will detect the onset of knock/ping so quickly, and at such a low level, that the driver will never take notice. Upon detection of even these minor levels of knock/ping the ECU will INSTANTLY "detune" the engine. The A/F mixture will be enriched "just enough" to alleviate, abate, the possibility of detonation.

And what happens after the engine is detune, it will try to go back to normal until it detects knocking again, then detune again. This cycle happens over and over again, that repeated slight knocking may or may not damage your engine in the long run. I guess I am not willing to take that chance.

You seem to be not aware that your ECU "knows" when the car is refueled.

[The G Man]

You seem to be not aware that your ECU "knows" when the car is refueled.

I assume when you say refueled, you mean using 87 octane and not filling up the gas tank. The only way the RX know what octane you are using is by sensing for knocks and pings, I am sure it doesnt have a on-board octane analyzer. The ECU is program for 91 octane, so it will always try to run in that mode even after the it is de-tuned due to knocking. As soon as it is de-tuned, the ECU will slowly try to go back to the normal mode, until knocking is sensed again. The ECU does not stay de-tuned.

[The G Man]

You seem to be not aware that your ECU "knows" when the car is refueled.

I assume when you say refueled, you mean using 87 octane and not filling up the gas tank. The only way the RX know what octane you are using is by sensing for knocks and pings, I am sure it doesnt have a on-board octane analyzer. The ECU is program for 91 octane, so it will always try to run in that mode even after the it is de-tuned due to knocking. As soon as it is de-tuned, the ECU will slowly try to go back to the normal mode, until knocking is sensed again. The ECU does not stay de-tuned.

[jaswood]

You seem to be not aware that your ECU "knows" when the car is refueled.

I assume when you say refueled, you mean using 87 octane and not filling up the gas tank. The only way the RX know what octane you are using is by sensing for knocks and pings, I am sure it doesnt have a on-board octane analyzer. The ECU is program for 91 octane, so it will always try to run in that mode even after the it is de-tuned due to knocking. As soon as it is de-tuned, the ECU will slowly try to go back to the normal mode, until knocking is sensed again. The ECU does not stay de-tuned.

No, what I was trying to say, granted, somewhat obliquely, is that once the ECU "discovers" that you have fueled with regular, it has no reason to "try" premium level POWER fuel mixtures until it "sees" that you have again refueled.

But even were it was as you say, continually(***) "pushing" the performance evelope, the result would be detected so quickly and at such a low detonation level that even long term engine damage would be minimum.

*** There are really only 2 causes, times, that detonation from octane levels might be an issue to be dealt with, 1, WOT, FULL cylinder fills, and/or, 2, engine lugging. With automatic transmissions this latter issue simply doesn't exist, the transaxle will typically be downshifted, and/or DBW will be used to delay rising engine torque, before the engine approaches the lugging point.

So, how often do you use WOT, for that is the only time a detonation "test", continuous test, might need to be made.

[The G Man]

I know that on some cars, the ECU will always try to run with the higher octane program continuously. Do you know for a fact that the Lexus ECU program only try to advance after a fill up?

Even a slight detonation may cause minor damage, it doesn’t have to be cause by an all out WOT, but simply by climbing a steep hill or towing.

[jaswood]

I know that on some cars, the ECU will always try to run with the higher octane program continuously.

Do you know for a fact that the Lexus ECU program only try to advance after a fill up?

For a fact..NO.

But why would a manufacturer do something as illogical, write firmware code, as "testing" for detonation without "cause". Once discovering that the engine is being fueled with regular why test for premium without cause..?

Even a slight detonation may cause minor damage

Yes, while that may very well be true, why do you think the manufacturer would use a firmware design that does that when there is an alternative method readily available..?

it doesn’t have to be cause by an all out WOT, but simply by climbing a steep hill or towing.

Other than the possibility of detonation due to carbon deposits, etc, there are only 2 conditions that might result in detonation.

1.) WOT resulting in a FULL cylinder fill, effective compression ratio being equal to actual, base/native, compression ratio.

2.) engine lugging. Note that this can occur regardless of octane level.

In the latter case the engine/transaxle ECU will ALWAYS downshift to the lowest gear ratio level that alleviates detonation. If that means downshifting into 1st, say for climbing an incline and/or towing, then you move likely than otherwise have the throttle wide open which puts us under rule # 1.

I have no idea just what might happen with lugging the engine due to the failure of the driver downshiftng appropriately with a manual transmission. Maybe a CEL indication or maybe even "you deserve the results you get if you're that stupid".

[The G Man]

I know that on some cars, the ECU will always try to run with the higher octane program continuously.

Do you know for a fact that the Lexus ECU program only try to advance after a fill up?

For a fact..NO.

But why would a manufacturer do something as illogical, write firmware code, as "testing" for detonation without "cause". Once discovering that the engine is being fueled with regular why test for premium without cause..?

Even a slight detonation may cause minor damage

Yes, while that may very well be true, why do you think the manufacturer would use a firmware design that does that when there is an alternative method readily available..?

it doesn’t have to be cause by an all out WOT, but simply by climbing a steep hill or towing.

Other than the possibility of detonation due to carbon deposits, etc, there are only 2 conditions that might result in detonation.

1.) WOT resulting in a FULL cylinder fill, effective compression ratio being equal to actual, base/native, compression ratio.

2.) engine lugging. Note that this can occur regardless of octane level.

In the latter case the engine/transaxle ECU will ALWAYS downshift to the lowest gear ratio level that alleviates detonation. If that means downshifting into 1st, say for climbing an incline and/or towing, then you move likely than otherwise have the throttle wide open which puts us under rule # 1.

I have no idea just what might happen with lugging the engine due to the failure of the driver downshiftng appropriately with a manual transmission. Maybe a CEL indication or maybe even "you deserve the results you get if you're that stupid".

What ???????

[jaswood]

"...What???????..."

Does that indicate a full and complete lack of understanding or only partial, specific...?

[The G Man]

Dont you think your tone is a bit condescending? I ask you if you know for a fact that the RX350's ECU program only try to advance after a fill up? and you went on about shifting gears in a RX350 with manual transmission.

[jaswood]

Dont you think your tone is a bit condescending?

No, absolutely not.

I ask you if you know for a fact that the RX350's ECU program only try to advance after a fill up?

And I answered in the most direct way possible...."NO!"

and you went on about shifting gears in a RX350 with manual transmission.

While not factual I felt it worthwhile to explain why it was LOGICALLY a reasonable assumption.

....

[The G Man]

Dont you think your tone is a bit condescending?

No, absolutely not.

I ask you if you know for a fact that the RX350's ECU program only try to advance after a fill up?

And I answered in the most direct way possible...."NO!"

and you went on about shifting gears in a RX350 with manual transmission.

While not factual I felt it worthwhile to explain why it was LOGICALLY a reasonable assumption.

....

Just wondering, what country are you from? We seem to have a communication problem.

[jaswood]

Dont you think your tone is a bit condescending?

No, absolutely not.

I ask you if you know for a fact that the RX350's ECU program only try to advance after a fill up?

And I answered in the most direct way possible...."NO!"

and you went on about shifting gears in a RX350 with manual transmission.

While not factual I felt it worthwhile to explain why it was LOGICALLY a reasonable assumption.

....

Just wondering, what country are you from? We seem to have a communication problem.

Speaking of being condescending....

[The G Man]

I dont think that was condescending at all, I did say "WE" and not "YOU".

[LEX-SV]

The amusing condescending thread or just read the owners manual for fuel requirement, whatever is easier. We know which one is more useful.

[4 the dogs]

with gas now going higher and higher and the 2012 uses the lower grade gas can the 2011 RX 350 be adjusted to use it. it has to be something simple they did not scrap the enigine.

also at the last car show we went to the leather seats in every lexus took on the dye off the blue jeans and every seat had been stained any one getting this problem/ think the leather is much cheaper than what I had in the last one.

[BadBrad]

Have now used 87 octane in the 2010 for 30,000 miles. No pinging and no problem. Owner's manual recommends higher octane for best performance (if you really feel the need to 5 more horsepower). Owner's manual also says can use 87 octane if that is all that is available.

Blue die from jeans can be removed with leather cleaners.

[2011RX350]

running lower octane gasoline is not a problem unless you miss the 10-20 HP or so you lose due to the engine mngmt system tuning out the predetonations. If you are doing a driver's ed or NASCAR event at a racetrack in 110F heat, by all means, use 93 or 94 octane, or higher. If you are just driving around like most of us do most of the time, who cares about the lose of 20HP at high engine loads and high ambient temperatures? Y'all need to use your left brain to think about this...