Briankim79

I was wondering what kind of gas people are using out there.

Arvin

91. Its the best we can get here in California.
we do have 100 octane fuel in some 76 stations, but I never thought to put that in a RX400h.

MadloR

There is the misconption that 87 octane fuel, called regular, is somehow of poorer quality than 91-92 octane, which is called super.

There is nothing superior in quality about 91 octane fuel over 87 octane fuel (regular unleaded). They are produced with the same tolerances and basically come out of the same hole in the ground. They are processed and manufactured IDENTICALLY, the difference being the additional octane ingredients that are added to reduce the flamability of the fuel under extreme load (like when pulling a boat up a steep hill).

Sorry to ramble, but my "fine point" if you will is to let everyone know that you will not gain additional fuel economy by using Super Unleaded. In fact, I get worse fuel economy using super unleaded 91 - 92, as well as 97 octane (found some in my area). If you are driving for fuel economy, like most hybrid owners do, then you are never driving so that the engine is under extreme cylinder pressures and temperatures, hence pre-ignition of the fuel is never an issue. Save your money, fill up with 87 Octane.

Cheers,

MadloR

Arvin

I have to disagree with you. People who design and build this car wrote in both the owner's manual and driving performance guide that this car's engine require 91 or higher octane for optimum engine performance. To fill anything higher than 87 into my Prius is a waste money because the engine of the Prius is design to run with 87 and won't recognized slower burning of all other higher octane fuels. The engine of the RX is design to run with 91 or higher. I will also think 97 octane is too high for the RX400h and its wasting money. The RX will still run fine if you fill up with 87 because the ECU retarded itself to decrease the chance of engine knocks, but you won't get the same performance and economy as 91 or higher octane. Also you are still risk your engine to knocking by always use a lower octane than the one require by the engine. I know it is your car and you have the right to fill whatever fuel in it. You properly won't see the consequence of always using 87 if you lease or not plan to own your car in long time. But please don't misguide others that 87 octane is the same as 91 octane in a RX400h because it is not, said by the people who design and build this car.

MadloR

Your replies and statements are self contradictory.

Ask yourself this, when you are driving for maximum fuel economy and savings, how often do you floor the gas pedal? How often are you tapping the full potential of the gas engine? How often do you think the engine is retarding the timing when driving for maximum fuel economy?

None. Exactly my point.

Hence the engine is never in the power band or in the area where demands put on the fuel require it to be the highest possible octane in order to help with pre-ignition.

Of course, you can waste your money on Super Unleaded all you want, but you won't be saving one iota of additional fuel and you won't improve your mileage. You will of course lighten your wallet in the process, by using super unleaded to try to achieve better fuel economy.

Cheers,

MadloR

herbvdh

Of course, you can waste your money on Super Unleaded all you want, but you won't be saving one iota of additional fuel and you won't improve your mileage. You will of course lighten your wallet in the process, by using super unleaded to try to achieve better fuel economy.

Cheers,

MadloR

Just to quote MadloR The owners manual says to use 87 octane on my 2006 RX400h have tried super 91 octane for several tanks and found that I got about 6% to 7% better gas milage. This I got from a taste of Lexus event. IMHO this is almost not worth the 20 cents more a gallon. I went from 25 MPG to about 27 MPG why should I make the gas station any richer than he is getting mow.

vulpasin

This is what I've posted in another thread:
Now, anyone will draw his/hers own conclusions

Still, Lexus insists on using Premium gasoline, why?

MadloR

Because the engine and ECU have been calibrated for a wide range of driving styles and needs. If you plan on towing heavy loads, or driving in extremely hot conditions, conditions in which higher octane will allow the engine to extract every last available horsepower / torque from the engine in order to perform under those extreme conditions. That is not to say that using regular unleaded will not perform as well (being the performing part, as in will the vehicle break down and die, no, it won't), it is just that the super unleaded will achieve the 1 to 3 horsepower more available from the engine without the need to retard the timing and bring the engine under a Non-Pre-Ignition state.

Isn't it nice to know that your 400h has been calibrated also for more spirited driving where super unleaded CAN be put to better use.

Cheers,

MadloR

P.S. I am not "telling" everyone what fuel to buy, I am just trying to clarify a possible misconception about fuel economy and the type of fuel required to achieve maximum fuel efficiency.

CrazyMPG

iTrader: (4)

hm...I thought the RX400h and the RX330 engines can use 87 perfectly fine. Lexus doesn't require you to get premium unleaded for those cars. My dealer at Longo Lexus said the RX400h would be fine with 87. I have filled it with 91 before, but I really didn't see much difference in MPG. I managed to get 28.8 MPG on regular unleaded for 1000 miles.

NeoNz

impressive

davidsong

i always use 91, but will use higher octane if its available. i always use higher octane to protect my engines; i buy my cars, i dont lease, so i would rather see them last longer than having engine knock or w/e later.

on my 2000 lx470, i've always use 91+ and its got over 110k mi and its still going strong (knock on wood). just my $0.02.

Overclocker

The RX300 and 400h may use a similar engine, but they are used in different ways and that’s what concerns me. The 400h has a CVT transmission that keeps the engine in its optimum rev range and changes the gearing around it. Depending on what that optimum RPM is, I wonder if the 400h was designed to use 91+, or if lower octane would be fine since it’s using only a small RPM range?

JimsGX

Has anyone noticed whether they get better gas mileage using a specific brand of fuel than another?

Jim

IS3_FTW

iTrader: (3)

Agree

lexus114

Guy`s, c`mon, everyone is truely blowing this whole reg.unleaded-premium thing out of control.And I know as fuel price`s continue to rise,we will probably have even more discussion`s re; this.I use premium now,but I believe sometime in the very near future,I will be down grading (in octane) not my vehicle,to pos. 89 or even 87 fuel.I have used the 87 octane before,and it doesn`t have the HP or the torque,but I didn`t use it long enough,to see a milage (mpg) diff. Now,if I start using reg. unleaded,and notice a significant drop in mpg, then I`ll stick to premium,As it would be a wash @ that point.Follow me? If you use reg.and get 2mpg or so less,then you may as well stay with premium,cause your not showing any savings,by reg. fuel.