So I have read and been told that the ES 350 can handle regular gasoline without knocking. However, in so doing, you will suffer "a decrease in performance"... Does anybody know how much of a decrease and what decreases? Is it horsepower, gas mileage, etc?

There will probably be a slight difference in HP......but I sure as hell don't notice a performance difference. It'll still accelerate from 0-60 in

less then 6.5 seconds!

When I bought my ES350 over a year ago I ran 91 or 93 octane gas for about ½ a year. I than decided to try 87 octane fuel and have been

using it ever since. The car runs very happily with this lower grade, but I might add, if the performance suffered I would once again go back

to the higher octane. There was NO difference in the mpg.

The main difference is whenever I fill up, my wallet is fatter.

Perfect. Thanks for saving me some cash!

I know the Engine ECU will compensate, but does it put the engine in a different load situation? I have used regular on occcasion in my RX but mostly use premium as recommended by Lexus...

The only way I can answer this is to tell you that my daughter, who lives in Minnetonka, Minnesota, and drives an '04 RX330 also switched from 91 octane to 87 octane, and found NO difference in performance or mpg either.

I might add that these tests were done at sea level, in mostly non-mountainous areas, with 1 to 4 passengers in the car, so the various load conditions in normal driving shouldn't be a problem.

I am a former Infiniti I30 owner who recently bought an ES350. I am on my 3rd tank of 87 Octane. One thing I did notice is that there is a slight hesitation. The next time I fill the tank, I'll go back to premium and see if the hesitation is still present. There is no pinging, and I used 87 in my I30 exclusively.
One additional unrelated comment was that the 2 Lexus dealers I spoke to (Lexus of Norwood, Ma and Lexus of Watertown, Ma) were both class A operations that made me feel very welcome. (They also enjoyed taking my money :-).

It is hard to tell the changes in gas octane as the engine will compensate.
It does get less power as you physically cannot use the full range of its timing advance with lower octane fuels.
It will change the throttle response and shifting on most drive-by wire vehicles also.

MY ls shfts like crap with lower octanes.

Timing is not longer used to adjust for fuel octane, not unless you have a carburator. The engine control ECU simply enriches the mixture slightly via longer injector "open" time to prevent ping/knock with a lower octane.

So, West, is this a major problem on the engine, will it carbon up faster, and how does it effect emissions? I have always used premium, however once in awhile have used middle grade or reqular...Does pushing more fuel in the cylinder cause any side affects on the Catylitic converters? just curious...

Wrong information!!!

More advanced ECUs found on most modern cars also control the ignition timing, Variable Valve Timing (VVT), the level of boost maintained by the turbocharger (in turbocharged cars), and control other peripherals.

Your statement beginning: "More advaned ECUs found..." is perfectly correct, but the way it was explained to me by the Porsche tech when I picked up my 2001 Porsche at the factory is that the adjustment to prevent pinging/knocking "under power, load" with lower grade fuels is done via controlling the mixture ratio.


I was surprised when I was told that in my travels throughout europe all I had to worry about was to not fuel with leaded.

Well, we're discussing Lexus ECU technology, NOT Porsche, so in effect, am I right to conclude that the information that you posted was wrong?

No, I was not, did not, discuss any issue beyond the ECU control of the fuel injection timing being used to adapt the engine to the use of a lower grade fuel. All of the parameters you mention, plus others, are also controlled by the ECU but in more of an all encompassing manner. I. E., regardless of octane rating.

And why would you, or anyone, assume that Lexus (NipponDenso, Denso US) control of this particular parameter, octane deviation/variation, would differ from Porsche (Bosch)?

Maybe I misunderstood this statement, "Timing is not longer used to adjust for fuel octane, not unless you have a carburator." This statement was dead wrong.
If you said that the ECU controls both timing and fuel/air ratio to compensate for variations in octane...then I could understand that. You're the one that was told by a Porsche tech that ignition timing was not involved with making these adjustments by the ECU. I guess you were misinformed.

Timing adjustment was NEVER a satisfactory method of preventing engine knock/ping due to low grade fuel or the driver "lugging" the engine down beneath the power band for some reason. But with a carburated vehicle the more satisfactory solution was/is simply not available. Nowadays with such powerful ECUs, highly sensitive (non-resonant type)knock/ping sensors it simply makes a lot more sense, and provides a much larger adjustment range, to change the injector timing period to adjust the mixture ratio and thereby more easily avoid knocking/pinging.

No, I was NOT misinformed, I have a full and complete set of Lexus shop/repair manuals for the 1990 LS, 1992 LS, 2000 GS300 & RX300, 2001 RX300, and the 2003 Toyota Prius, along with a set for almost every other vehicle (mostly Fords), airplane, tractor I have ever owned, own. The Lexus/Toyota diagnostic sections never bring up the issue of ignition timing in relation to the use of "improper" fuel grades. As a matter of fact when I bought my very first Lexus I had been unaware of the Premium Fuel ONLY requirement but I was subsequently assured that I could use regular fuel for the entire life of the LS and the only problem would be degradation of HP/Torque.

Think about it in a little "more" depth. The reason you get knock/ping with a "too" low octane in a carburated engine is because the compression ratio along with the octane/mixture is either approaching the point of dieseling or due to the engine output torque requirement being lower than needed (lugging) to do the "work". In the latter case the explosive, EXPLODED, flame front is moving faster then the piston will/can move downward and so you get knock/ping (rattle??) And what can you do with timing to overcome dieseling in either case, advance? retard?

NOT...!!!

In the olden days enrich the mixture by changing the carburator jetting......

Nowadays......

Oh, in them olden days the only real reason, cause, for adjusting the timing, fixed or dynamically, using mechanical or ECU techniques, was to get to, keep right on the "cusp" of dieseling/detonation/preignition without actually reaching it, I.E, get the MOST performance from the engine given the fuel grade its jetted for.

And yes, there was sometimes an exception, pre-ignition due to engine over-heating, superheated carbon particles and the like remaining, lodging, within the combustion chamber. And while the timing could be retarded to alleviate some of the adverse effects from this and thereby lower (maybe) the explosive "rate", knock/ping from this source could not be in any way overcome via timing adjustment.

Bottom line... Does regular gasoline hurt a ES 350 engine? I do not mind the HP/Torque performance loss, but I do not want to damage the engine at all. I got quite lost in the technical discussion...

No.

At least not unless you have a manual transmission and regularly abuse it by lugging the engine.

Thanks all!

All I can say to you is read this>> http://en.wikipedia.org/wiki/Engine_Contro...Ignition_Timing

"Wiki" is now correct, corrected.

I was trying to stay away from this topic, but I can't resist. Ignition timing will change to compensate for fuel octane, as will pulse width of the fuel injectors. Ignition advance constantly changes and you can see it using a scantool, especially when pinging/knocking occurs. I don't know about Bosch systems but Lexus ECU's will change ignition advance all the time. Lower octane fuel will reduce engine power and the quality of the trans shift. ES350 or RX350 engines they have short skirts on the pistons, & cold start piston slap does happen on these GR engines, and most people don't notice. All the cases(86 cases) of piston slap I've seen have been from people that use regular fuel, Every single complaint for cold start piston slap has been aleviated by using premium fuel. I work for a dealer and have dealt with many issues regarding regular and unleaded. Use what you want, premium fuel will make driveability better.

You're a real wise guy!

Okay, if you take a look at the distriburtor mechanical internals in my 78 Porsche 911 you will find both a vacuum advance and centrifical advance via springs and weights. Obviously the ignition timing changes as a function of engine load, loading (vacuum), and engine RPM. I remember that one of my Ford V8's had a second vacuum system source so as to more accurate "map" the ignition timing to actual engine operating conditions.

With the 78 if I wish to switch to premium, higher octane, fuel and actually take advantage of same, I would to change the jetting or at least manually change the "static" BTDC ignition timing if not "retune" the entire vacuum and centrifical dynamic ignition advance mechanisms. I think we all know what was most commonly done.

Now, "LEAP" forward from 1978 to 2007.

You can now control the timing, statically and dynamically, to the Nth degree. But in doing so you would certainly want to keep it advanced to/on the very cusp of best/most advanced timing less actually crossing over to the knock/ping parametric regions. Rule # 1.

But with EFI you also have full and complete control of the mixture ratio (insofar as CARB and the EPA have set limits).

Given the two choices, as an engineer, keeping rule # 1 in mind, would you retard the timing additionally, even greater retardation level, in order to accommodate the lower octane fuel, or would your attempt to keep HP/Torque roughly equal by increasing the level of fuel to be mixed with air and thereby avoid the knock/ping operating region?

No one need answer that.

Read this> http://en.wikipedia.org/wiki/Air-fuel_ratio
Than you can change it to suit your hairbrained ideas like you did before.

Why increase the amount of fuel to reduce pinging, and increase emissions, when you can change ignition timing. These days it's about lowering emissions, not keeping power/torque at it's peak. WWest you should read a live data list from a Lexus ECU and you'll see how much more timing changes than injector pulse width, especially during detonation.

Boy, do I really, REALLY know how to miss-state, miss-represent, my own case, argument.

Let's start out using today's more likely scenerio wherein the vehicle engine was designed primarily for the use of premium, 92 octane, fuel.

Premium fuel is less subject to predetonation, dieseling, so we can begin by raising the compression ratio above that which would seemingly be required for using a lower grade fuel. Let's also throw in the most ignition advance, statically and dynamically, we possibly can in order to achieve the highest level of HP/Torque possible from each ounce of that EXPENSIVE high octane fuel.

Okay so far..?

But now we want the owner to have the capability of fueling with 87 octane if the need arises.

Can't lower the compression ratio....??

Lower grade fuel, 87 octane, under the high compression ratio of "this" engine would undoubtedly be more subject to predetonation, dieseling.

Timing....??

Retarding the timing will do little good if the knock/ping is the result of dieseling, self-preignition of the A/F mixture.

Advance the timing...to a certain extent, yes.

Pre-ignition due to dieseling often results in an uneven, "ratty", flame-front progression and "tweaking" the timing forward a slight bit might provide a more widespread flamefront and thereby less stress on the engine. Not recommending this as a practice in any way, just thinking out loud.

So, advance the timing..??

NOT...!!

Sorry, I used a poor example, a really poor example, using my 78 Porsche.

So, how do we prevent dieseling of a low grade fuel when used in an engine with a compression ratio tuned/designed for the use of premium?

Enrich the mixture.

Sorry, the referenced Wiki statement regarding proper/correct A/F ratio is already perfectly aligned with my own.

To quote:

"A stoichiometric mixture is the working point that modern engine management systems employing fuel injection systems attempt to achieve in light load cruise situations."

Operative term being...

LIGHT LOAD CRUISE SITUATIONS.

My 2001 C4 would not likely be able to produce its rated 300HP were the mixture left at the stoichiometric ratio as the throttle is opened farther and farther from the otherwise meager light engine loading cruise requirements.

At high throttle openings, high engine loading, the "front" oxygen sensor(s) otherwise used to monitor for proper stoichiometric ratio (no unburned oxygen in the exhaust gasses) are ignored. Instead the MAF/IAT sensor outputs are used to control the mixture at a typical 12:1 ratio or beyond. A seond point, somewhat important, is that during light loading operations the MAF/IAT sensors are "calibrated" via the front oxygen sensor output monitoring. If the MAF/IAT signals should for some reason drift from the previous calibration point the ECU simply "learns" the new one.

That's why those ebay gadgets that modify the IAT signal output, seemingly to result in a higher mixture ratio and thereby more HP from a given engine design, simply do NOT work.

On the other a more sophisticated design, one that only modifies the IAT signal upon/with high throttle openings, might well work.

Haven't yet noted that any of those Ebay device vendors want, or even know, to go to that extra effort.

I believe the recommended octane rating to use is 91. I assumed that the Lexus engineers did a lab study and concluded among other things that 91 is the optimum (RON + MON)/2 octane to use. I accept this irrespective of all the wonderful discussion on octane relationship with engine ping which I find very helpful and informative.

Now here in Texas we have three choices: 87, 89 and 93. If I want to use a gasoline with octane of 91, I would think that the best way to achieve this is to blend 89 and 93. The question is what is the correct volume mix? I am a chemical engineer and I can tell you that there are complicated formulas to achieve a certain blend of gasoline based upon the properties of each blending component. In a refinery there are several tanks of components which are mix to finally arrive at the desired specification of the gasoline product. Octane number is only one of the determining factors but the most important.

In a practical point of view I think that a 50-50 mix of 89 and 93 will be approximately close to achieving a desired octane of 91. Therefore if I fill up and needed 10 gallons, then I would start with 5 gallons of 93 then followed by 5 gallons of 89. Yes it will take more time. I am not sure if you have to swipe your credit card twice for this. But I will do this next fillup.

The main purpose is to try to use the recommended octane of 91. There will be some savings but this is not my main objective. I dont want to waste resources.