mandyfig

Makes sense to me.

AM1

iTrader: (6)

whatever, the rx isnt a performance car or something.

vlamos

Obviously there is a fair bit of tolerance when it comes down to fuel octanes as in Australia our high otcane fuel is 98, so how do Lexus get round all the different octanes levels produced world wide. I know using 98 makes a big difference to the performance / fuel consumption and also your bank balance.

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. Lexus engines have the same tolerances for fuel worldwide. There is just no standard way of saying the type of fuel required

jmaynard

I don't care if it is or not. Lexus says to use 91 octane fuel in it unless you can't find it. I would no more go against that requirement than I would the requirement to change the oil every 5000 miles.

geko29

IF they changed any of those things, as you say, the HP/torque numbers would be markedly higher than the same engine in a different application. Instead they're identical or the Lexus extracts 1 more HP (0.3% increase) than the comparable Toyota.

Yeah, you know what was done to it? They REPLACED THE ENGINE. The new one has MORE DISPLACEMENT. A 3.5L makes more power than a 3.3L, it's a relatively simple formula. They also replaced the engine in the Camry, Avalon, RAV4, and 2008 Highlander with this same new motor. And they all make about the same power numbers (WELL within the range explained by differing intake/exhaust systems) on 87 Octane. The Highlander, which is most like the RX and will hence have the most similar intake/exhaust track, makes EXACTLY the same power numbers as the RX350, on 87.

The G Man

Just use 89 octane, its only a $1.50 more per fill up. Usually 89 ocatne is tested around 90 octane anyways.

biff44

So,you think they replaced the entire engine to add 0.2 liters of volume? Pass over some of what you are smoking dude!

They made a minor change in the piston/crankshaft/cam shaft to get that 0.2 liters. That change, along with the new computer programming, is why they now recommend the higher octane.

AM1

iTrader: (6)

im going to have an rx350 for a few weeks. im going to put 87 in it and see what happens. then im going to put 87 in my rx330. hey geko29, dont listen to these people they can keep believing the premium fuel crap. i dont know how many people ive talked to that own lexus cars and feel that they are far more superior to "regular" toyota cars, even when back a few years ago they were sold as toyotas everywhere else in the world. heck im going to put gas from arco, where they have no high tech additives. i must be crazy, yea?

harleydjce

A little bit more than just a minor change in the piston/crankshaft/cam shaft. They also changed the injection system. Regardless, it's a new engine even if it is just an evolution of the old 3.3L

The G Man

The new 3.5 is quite diff. from the old 3.3, check out this artile:

http://www.worldcarfans.com/news.cfm...rx350-in-depth

harleydjce

I stand corrected. It is a very different engine. Thanks G Man!

TunedRX300

2gr-fe definitely has a different design than 3mz-fe. Interestingly the compression does not change much @ 10.5, not sure octane rating for the gas really needs to be bumped up to 91. Again, follow owner's manual and cross check Toyota models.

The dynos I quoted from Lexus has 2fr-fse, it has a much higher compression of 11.9 and a different DS-4 twin fuel injection. Very nice engine, in fact, I am planning to get one myself!

mandyfig

The 350 rocks! I still love my 330 though.

jmaynard

Please stop with this red herring. As I said before, I don't run 91 octane fuel in the mistaken belief that my RX350 is somehow superior to a Toyota. I ran 87 in my RX300 with no qualms at all. I do it BECAUSE THE MANUAL SAYS TO, pure and simple.