xfirechief

Sorry but I too get 1 1/2 to 2 MPG better with 93 Octane. When it is only 10 cents more then midgrade I go for it.

AV8R_BOB

That is another one of my concerns with premium. I read a report indicating something like 5% of gas sales are premium and typical turnover rates at the gas station are much lower for premium, i.e. it's older when you buy it.

AV8R_BOB

That's true, at 15,000 mi/yr the extra cost of premium amounts to about $200/yr.

AV8R_BOB

Actually that's not correct. Pinging is pre-ignition (fires too early).

AV8R_BOB

What octane is that engine rated for? If regular 87, then running premium will NOT get you better MPG. You may THINK you are, but it's not.

Also for any MPG test to be valid, you must run two tests running the same route under the same conditions (outside temp, vehicle weight, etc). Ideally it should even be a blind test so you don't know what's in the tank, lest that affect how you drive. If you are just checking MPG during your normal driving around, that's not a good test and I'd discount a 1.5 mpg difference.

AV8R_BOB

That's true, because a higher compression ratio requires higher octane to avoid pre-ignition. But if the engine has a compression ratio that only requires 87 for proper ignition then burning higher octane gas has NO benefit.

AV8R_BOB

Strange, no one is forcing me to read any of this.

All that is true, IF Lexus has designed the engine to run on premium. But I think you are missing my point... I'm trying to determine if in fact the engine does require premium or not. I am not saying that if the engine is designed to run premium then I want to run regular. That would not be smart.

Again, the apparently identical engine in the Highlander is rated for 87. If the Lexus engine is in fact the same as the Highlander's, then that means it can burn 87 also with no adverse effects. That also means the premium spec has some motivation behind it other than engineering.

The sales rep sent me another email today saying he and others have asked Lexus the same questions but don't get any answers.

AV8R_BOB

What octane does the book require in that vehicle? I "think" it's regular. If so, you should not see any difference in MPG or performance running higher octane assuming you run a good test.

Lexmex

The only real advantage I have really heard about is when using low octane at higher altitudes, such as when I lived in Mexico City (but the low octane gas there had a load of sulfur in it and after losing one precat and one regular cat when I was basically forced into a situation where I had to use it it was basically on my s... list except for a few experiments).

Lexmex

I welcome your comments and welcome to the Club.

My RX300 is quite a bit modified so I am going to run a test on 87 octane (Chevron) for a bit to see what if any difference I notice, keeping an open mind, and reporting back results.

Just found my manual in some boxes,

On the back cover it states:

Fuel selection:

Select Octane Rating 87 (Research Octane Number 91) or higher. For improved vehicle performance, the use of premium unleaded gasoline with an Octane Rating 91 (Research Octane Rating 96) or higher is recommended.

MARINE

And the 2008 IS250/350, 2008 ES350, 2007 RX350, ES350 manuals all say these choice words :

Use of unleaded gasoline with an octane rating lower than 91 may result in engine knocking and significantly reduced performance. Persistent knocking can lead to engine damage and should be corrected by refueling with higher octane unleaded gasoline.

It also states 87 may be used if 91 is not available. Tell that to Lexus HQ when they void the warranty repair. Unless you live in another country, premium is nationwide. Why take chances for a few cents more?

Would you not want your car to run at optimum performance?

If putting 87 in your car makes you happy, IMHO, buy a yugo

I know, I had ALL the models stated in my siggy. Run 87 and get peepee (wouldnt want to use stronger language lol) mileage and peformance.

Lexmex

I think for many it's an economic issue. Although we are fortunate to have a luxury vehicle in our Lexuses, I know quite a few people who got themselves in a pickle and our trying to make ends meet (through no financial fault of their own, but just the economy) and watching both how they drive and what they can afford to put into their tank. That's one reason I am running my test with 87 to see for myself what the effect is not just for myself, but also for the benefit of the group. Ideally, I've always tried to give my RX300 (especially when I was in Mexico) the finest in fluids that I could get handily, though I had really no choice (except for some racing gasolines) but nationalized gasoline. I can still afford Super Unleaded, but because of the unique modifications I have on my RX, I am very curious to see their effect with 87 octane at sea level.

AM1

iTrader: (6)

i agree with you on that, my original post i was being quasi-facetious, since saying what i really think will probably spark a war like it did months ago.

i asked my service advisor that and he said the same thing, they really dont have an answer for it, they just said we know that you can run 87 safely and it runs fine. he said lexus HQ hasnt given them a real answer either, kinda makes you wonder.

let us know if there is anything significant. unless your car is under forced induction, i doubt the difference will be neglibigle.

uh....was that comment about buying a yugo really necessary? and when did 87 automatically guarantee that if you have an engine problem that they will void your warranty? uh they have to prove that putting lower grade gas is the sole cause of whatever problem is in question.

good to see someone who sees it on both sides of the proverbial fence. for me i can afford to put premium, heck if i wanted to i could afford to put racing fuel every fillup. the reason i dont is i dont think i should waste money when its unnecessary. the next car im looking it will possibly be turbo or supercharged, for those types of engines i will put premium since it will really need it not like the car i have now, which uses a low compression engine naturally aspirated. after all "a penny saved is a penny earned".

The G Man

AM1, if I lease my car, I wouldnt put in 91 octane either. Thats why I dont buy used lease returns.

Joeb427

iTrader: (1)

My RX is leased and believe me,there are other reasons not buy a lease return too.