JJ_BPK

Hay Guys

If my feeble old mind isn't slipping to much,,, gas octane is an inverse operator and does not have a lot to do with horse power or mileage. Also higher octane is not "better",,, it's just more expensive to make and in fact may give you less mileage.

The higher the octane the cooler the burn for a given cylinder pressure,,, The lower the octane the more violent the gas mix, Get it low enough, say 20 octane, and it will explode on contact with air, no spark needed. Get it high enough, say 220 octane, and C4 won't ignite it...

Why higher octane??

Engine KNOCK happens when you have thermal pressure-induced self-ignition,,, the engine PRE-FIRES the gas mixture before the cylinder has completed it's upward swing. When you have nock you use a slower less violent gas,,, ie: you up the octane to the point that it won't fire no mater what the cylinder temp and compression is,,, unless there is a very hot spark.

I'm not an petrol chemical engineer and you may want a more complete explanation, try this: http://www.rxp.com/Octane.htm
Or for even more information try this: http://www.seansa4page.com/resource/octane.html

There are probably simpler, more preliterate explanations somewhere, maybe some can list them...

Net: If your engine is happy with 87 octane, you should be happy... My mileage is up to 22.6 around town on 87 octane gas/corn-alcohol L-cheepo,, it' all we get on this Island,, no knock, I be happy..

Daddy-O

FWIW, here's the official Lexus corporate line
regarding the RX 300 and Octane Ratings:

"Select Octane Rating 87 or higher. For improved vehicle performance,
the use of premium unleaded gasoline with an Octane Rating of 91 or
higher is recommended."

mikey00

In my own tests with both my 2000RX and 2001RX, octane made no difference in performance or gas mileage. If you read back through the old posts on this board and Edmunds you will find the same results from many others. If you are getting better gas mileage it's only because your wallet is lighter.

sugarpie

I'm a new owner of a Black RX300 with spoiler, navi the whole nine yards, and so far, I get about 21-22 mpg. I drive city and freeway, but I read my manual and it says not to drive over 55 during the first 1000 miles. So I haven't. It also said to accelerate slowly and brake slowly, so I have been doing that too. It makes for a pleasant drive to work. My carpool co-worker says I have ruined her for her car, now she feels like she's riding on a tractor (Honda Passport). I thought my mileage would be much worse, so I'm happy that I'm doing 21-22 mpg, according to the computer in the car.

Daddy-O

sugarpie,

Welcome to ClubLexus.

Tell your friend to trade in her tractor and buy an RX 300.

Just letting her ride in it should sell her on it.

Pilot

I use a fuel additive called RXP which is unique in how it increased the fuel combustion temperature of the burning gas, and burns off old carbon that has formed in the combustion chamber, valves and top of the piston. I use this in my Honda Goldwing also. I like a clean engine on the inside. I also only used fully synthetic engine oils, with OEM factory filters. RXP fuel additive can be bought at Wal Mart. Do not follow the directions on the bottle for mixing. I have spoken to the factory rep, and he said you only need to add 1 oz for each 10 gallons of fuel, to get the same effect. So a 12 oz bottle can be used for about 6 fill ups.
This same company makes a additive for hotter flames in welding torches, where the metal is then cut faster and cleaner with a hotter flame, resulting little surrounding heat transfer to the metal that has been cut. This product really works and I have used it for about 2 years with excellent results.

http://www.rxp.com

Pilot

2001 RX300
91 LS-400
98 Honda Goldwing GL1500

LexRX

I have slowed my highway driving from 75-80 mph down to 65-75 - This is since my first speeding ticket a few weeks ago.

I now get over 25 average mpg traveling at 65-70 mph on the highway, which is about 2-3 mpg better than I was getting at the higher speeds.

At 80 mph and above the gas mileage on the RX really starts falliing. The rpms reach 3000 plus at such high speeds. I could see a fifth gear helping with this.

cephraim

What results do you experience with this stuff and that ratio? Are you adding it to 87 octane or higher?

Eph

Edit: Pilot, took your post outside the quote.

GR8TSCOT

iTrader: (1)

Three things you can do (other than change how you use the loud pedal):

1. Better airflow (K&N filter, less restrictive exhaust)
2. Reduce mechanical friction: use synthetic oil in the engine AND THE DIFFERENTIAL, if possible.
3. Reduce rolling resistance. Go to fuel-saving tires (eg Michelin Energy MXV-4 plus)

Of course, 2-wheel drive will always get better mileage than 4-wheel drive, because of weight & mechanical friction. Not much you can do about that!

p1fcl01

Yes, I agree if you drive under 70 mph, you will get better milage. But who does that!!!

I drive mostly city, I do live in NY with the worst traffic.

I have installed K&N filter. The begining I was getting 20-22 mpg, but now I get about 19 - 21 top.

K&N do give you a bit more mpg, but drive slower get s you more.

Don't go by the mpg on the computer, it doesn't work............it's off by 1 - 2 mpg sometime.

Regards,
Frankie

ganglandstyle

Interestingly enough, I noticed that when I changed the tires on my 2001 (from the original stock Bridgestones to new Michelin Cross Terrains) the MPG seemed to drop about 1.5 MPG.

Obviously, the circumference of a worn tire might be less than the same tire when new, but would this explain the difference between a new tire and an old tire? Does the Michelin tire offer more rolling resistance than the worn Bridgestone?

The total MPG seemed to go from 19.5 in mixed urban driving (FWD) to 18 under the same circumstances.

---just food for thought

ederny

I would think you'd get better milage from the Michelins from the reports I seen about rolling resistance. The tire shop did put the right pressure (i.e. the same pressure) in the new tires, didn't they? But that is a big drop even gfor a few pounds. And we assume, you didn't change tire width either?