mandyfig

The RX330 Manual says 91 Octane too, right? Or does it say minimum 87 OCT? But recommended 91 for optimum performance?

TunedRX300

Premium gas is more of a brand. It is a 91 octane rating gasoline with a nice name. Actually the same gas was called "supreme" in California couple years ago.

Automakers know that owners feel "guilty" by not putting "premium" gasoline into the car, as if the car is mistreated. Search on the maintenance forum you will find heated discussion. In fact, owners demand luxury car brands to require premium gas. Another member posted in one year Lexus recommendated 87 and above for ES300, the next year 91 is recommendated with no change in engine. Obviously, the change makes no technical sense, only to make ES more "appealing".

Fact is 91 octane rating gasoline is less volatile than 87 octane rated, the engine must have high enough compression to take advantage of higher octane or gasoline will not be completed burned. How do we know what is the designed octane rating for the engine? Look for Toyota AND Lexus recommendation for the same engine and don't assume that Lexus cars must use premium gas.

For example, fact is Toyota Avalon uses the same 2gr-fe engine but 87 and above is recommendated, you know it is pretty fishy if Lexus recommendate 91 for the ES and RX.
http://www.theautochannel.com/news/2...19/207902.html

At the end of day, it is a personaly choice. For me, I go with Lexus' recommendated octane rating but cross check Toyota's recommendation of all 2gr-fe based cars to get the REAL recommendation. Yes I can afford to pay $0.20 per gallon but what does that give me? If gasoline is really left unburned, my catalytic convertor will suffer and I LOSE power.

BTW, there are always free additives, just go to Autozone and they always have free brand name fuel additives free. Last month I got 2 bottles from Chevron Techron Complete Fuel System Cleaner free. Currently STP Complete Fuel System Cleaner is FAR at AZ.

anulex

I dont care about the the ES300 and the ES330. My concern was with the ES350. However, i use the term 'premium' as anything over regular. However, if my car says 87 octane or better, you can bet its getting 87. If it says 91 then its getting 91. however, it calls for 93, that sucker will get 93 or i am not buying that car

TunedRX300

Exactly, "Premium car get premium gas" statement should be double checked and not assumed that it applies to all.
More often than not Lexus owners just assume 91 is the minimum recommendated octane rating without even reading the owner manual. I have seen one moderator caught himself using 91 but his owner manual states 87 is the minimum.

harleydjce

There is already a thread on this "Rx 350 Which Octaine Gas do you use".

Some quite valid points around premium vs standard fuel. Octane is not the only issue.

Here's the link https://www.clublexus.com/forums/sho...=275586&page=4

jmaynard

The 2007 RX350 manual says minimum 91 octane, and that lower can be used but performance will suffer.

My 2001 RX300 recommended 87, so that's what I ran.

For me, I'm not about to spend $45K on a vehicle and then cheap out on the gas against the manufacturer's recommendation.

AM1

iTrader: (6)

its in the very back of the manual. it recommends higher octane but NOT required. I really hate how people asume that since its a luxury car that it has to have better gas. The engine in the rx330 was the same as the engine in the camry and the engine in the rx350 is the same as the engine in the avalon,camry, rav4, etc and all the toyotas use regular, same engine, so whose the fool putting in premium? and seriously lets all drop the whole you can afford a 45k car blah blah you should be able to afford the gas. That is not the point, the point is spending more on something then what is necessary.

biff44

Is it really the same engine? Just because the block is the same means very little. A few thousandths difference on a cam shaft lobe can mean the difference between needing high octane or not. Also, the way the computer programs the engine makes a big difference.

I am going to make a guess here: since the RX350 has a small horsepower increase over the RX330, they did some minor thing to the engine to get that horespower, and that might be when the "recommended" to "required" 91 octance gained some meaning.

mandyfig

I read the Manual for the nth time, it says 87 OCT. Does this equal to the OCT we see on the gas pump?

What does Research Octane 91 mean? I guess I should click on the link and do more checking...

I think we run the risk of getting this thread merged or even closed. The OCT talk has not simmered down....for now, I will use 87+93, 50-50, compromise.

harleydjce

Extracted from Wikipedia:

"The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel through a specific test engine with a variable compression ratio under controlled conditions, and comparing these results with those for mixtures of isooctane and n-heptane.

There is another type of octane rating, called Motor Octane Number (MON) or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, a higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON. Normally fuel specifications require both a minimum RON and a minimum MON.

In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in the United States, Canada and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, would be 91-92 in Europe. However most European pumps deliver 95 (RON) as "regular", equivalent to 90-91 US (R+M)/2, and even deliver 98 (RON) or 100 (RON).

The octane rating may also be a "trade name", with the actual figure being higher than the nominal rating.[citation needed]

It is possible for a fuel to have a RON greater than 100, because isooctane is not the most knock-resistant substance available. Racing fuels, straight ethanol, AvGas and liquified petroleum gas (LPG) typically have octane ratings of 110 or significantly higher - ethanol's RON is 129 (MON 102, AKI 116). Typical "octane booster" additives include tetra-ethyl lead and toluene. Tetra-ethyl lead is easily decomposed to its component radicals, which react with the radicals from the fuel and oxygen that would start the combustion, thereby delaying ignition. This is why leaded gasoline has a higher octane rating than unleaded."

Basically 87 Octane US = 92 RON

The G Man

The RX300 and 330's manual saids, min 87 octane. The RX350's manual saids 91 octane.
Althought the 3.5L engine share the same block as the avalon, camry and the rav4, the difference between the 2 engines are:
The Toyota version of the 2GR-FE engine: Bore at 94 mm but stroke is reduced to 83 mm. Output is 268 hp (200 kW) at 6200 rpm with 248 ft.lbf (336 Nm) of torque at 4700 rpm on 87 octane.
The 91 octane version provides a small boost in performance of 4 hp to 272 and 6 lb-ft to 254. This version features Toyota's "dual-VVT-i", variable valve timing on both the intake and exhaust cams. Valves are driven by roller-follower rocker arms with low friction roller bearings, and a unique, concave cam lobe design to increase valve lift over the traditional shimless lifter type system of the 1GR-FE. This increases overall cylinder head height to accomodate the slightly taller roller rocker system. Moreover, the cylinder head is segmented into 3 parts: valve cover, camshaft sub-assembly housing, and cylinder head sub-assembly. As such, this valvetrain is used across all other GR engines with dual VVT-i.
With gas price so high these days, Lexus knows that using premium gas is actually a negative as far as markerting is concern. They would not require preimum gas unless they feel that this version of the engine needs it.

mandyfig

Dave, that was fantastic! means that 87 OCT is the standard to use. But to each his own if premium suits you!

TunedRX300

Dual VVT-i is a feature for both Toyota and Lexus model, as long as 2gr-fe is used. Here is a link on Avalon
http://www.toyota.com/avalon/specs.html

3.7 x 3.3 inches are bore and stroke for both 2007 RX350 and Avalon, according to this link.

http://www.automotive.com/2007/12/to...4;14&strTrim1=

The difference is max HP and torque are also caused by different intake and exhaust designs. Prime example is GS350 and IS350, same 2gr-fse engine, same gas, different intake and exhaust, peak torque and HP have slight difference
Official dynos from Lexus Japan
GS350

IS350

mandyfig

Awesome info! You the man!

AM1

iTrader: (6)

hahaha and yet we are still arguing about octane ratings.