billy44bo

I think it were you live is how much extra octane you need. Here on the coast there all not many hills it is all flat and were they have mountains with the 10+ grades we might need it . the large hill here are only a 2% grade at best and we have no snow just a lot of rain 65+ inches a year

quantfutur

Lexus 114 - we have the same model/yr. Will the higher carbon element in the exhaust from running with 87 ultimately do damage to either the engine or cat./exhaust? Frankly I don't care much about 'performance' so much as to prevent serious (i.e., costly) damage later.

MrBruin09

I use and will always use premium. It costs me less than $3.00 more per fill up.

infinirx

Yeah $3 is nothing. If it were $10 I might downgrade while I am counting pennies but $3.

lexus114

Probably way down the road yes. I.e cats will probably go bad before they should,Air/fuel ratio sensors. The motor actually works harder on 87,has higher exhaust temps,less power,hotter internal temps (due to timing retard) All this is why I just cant justify using the regular,and as mentioned it`s only a few bucks more to use premium. It`s a win,win scenario.

quantfutur

Lexus 114 - Could using 87 have caused my cat. to deteriorate in the '99 RX 300 (reg. unleaded was recommended for that model) at 165-170k miles? Or is that normal wear/tear?

Thanks

lexus114

It`s very possible. Did you get the rotten egg smell a lot? like I mentioned above,the exhaust temps are higher on reg. due to the timing being cut back. I also believe using 87 octane is what helped to cook the oil on some of the older RX`s Higher head temps etc.

billy44bo

Here is the deal it is the same engine that they put in the Avalon, Camry , Rav4 and others
However, All Lexus engines are rated using 91 octane, Toyota rates using 87 that is why the Lexus shows 275 hp @ 6,200 RPM and Torque at 257 lb-ft @ 4,700 RPM while the Toyota rates it at 3.5-Liter V6 DOHC 24-Valve Dual VVT-i; 268 hp @ 6200 rpm; 248 lb.-ft. @ 4700 rpm. IF you need or want the extra HP and Torque use the 91+ or if you do not want to give any more that you have to big oil use 87 and have a good life.

lexus114

no need to get upset over it. use what you want. I use whats best for mine thats it. Being around engines since i cane remember anything tells me not to run a motor on retard timing. period. these motors work hard enough due to the size/weight vehicle their in (power to weight ratio) why make the damn thing have to work even harder?

Adamjeeps

Lexus114, I agree with you. I would also be willing to bet Lexus would not honor a warranty claim on your engine/fuel system if they detect 87 octane is being used. My manual clearly states to use 91, so I will do just that. I knew that before I bought it. It is only about 10% more expensive, and if it means I get more performance and better mpg, not to mention the tuning issues mentioned above, why would I use 87?

lexus114

Thats a good question my friend why would you? Makes total sense to me for premium ,others have a different view of it I suppose. I`ll be honest here, I tried the regular in my last RX (an 01) and my current 05. Mostly because the manual states that premium is recommended,not required. I had less power with the a/c on,ran out of steam past 70 on the highway,exhaust smelled bad,and over all just didnt run as smooth. And I did a few tanks of it,not just a fill up. Oh,and millage went down as well.

jfelbab

I find it is also an economic good choice to choose Premium. I get around 2 MPG more MPG using premium on the freeway. I've made about a dozen 1500 mile road trips over the same route to verify this. When I can travel further on a tank and pay less per mile that makes sense. The math goes like this.

Premium.
I get 26 MPG. Typically a 15 gallon fill will cost $54 at $3.60/gal. 15 gallons will allow me to travel 390 Miles for $54 or 13.9 cent per mile.

Regular.
I get 24 MPG. Typically a 15 gallon fill will cost $51 at $3.40/gal. 15 gallons will allow me to travel 360 Miles for $51 or 14.1 cent per mile.

For me, and my interstate driving, I am better off financially using premium.

As a side note, My RX330 smells of rotten eggs when I use regular. This disappears when I burn premium. I've had the vehicle examined by Lexus on several occasions and had a TSB done to reduce the odor but the facts are that there is incomplete combustion with regular and it causes my cat to stink. Continuing to use regular would eventually destroy my cat.

If I shop smart. like xfirechief, the economics would be even stronger in favor of using premium.

lexus114

I cant believe you get 26 mpg on the highway? the best I ever got was 23.8

jfelbab

I actually do better than 26 MPG. I was being conservative. Here is my MPG chart from day one. You can see my road trips and can easily identify where I used Regular and where I used Premium.

quantfutur

Lexus RX114 - I did have a carbon-y smell with the '99 at high mileage but there was a small oil leak and the smell went away once it warmed from start-up (e.g., a couple minutes).

jfelbab - Until yesterday's fill-up with 87 my '05 RX330 has only had premium. And mileage is 19.1 according to the monitor. 26 is incredible!

Btw, was there any major change to engine from 330 to 350 because 330 had minimum 87 and 350 seems to require 91+.

The BP station I have been going to has a 31 cent difference between 87 and 93.