This is NOT A DEBATE about what octane to use... please don't turn it into one.

I recently let one of my friends borrow my RX300 and he didn't know it "requires" premium fuel (93 in my case). He filled it with 89 (mid-grade).
When I got the car back I didn't ask him what he filled the tank with, I assumed he knew it would need 93. But, anyways when I was driving it the RX300 felt so weird, I had to press the throttle more to get up to speed, and passing required me to press the pedal more, also the hills felt harder to climb. So, once I got home I checked all the oils, inspected everything possible. And still no go. So I blew it off, and left this morning to go to PA. Got back just now, and had to fill up on the way back (filled up with 93). As soon as I got on the highway again I felt the difference, much more throttle response, what felt like faster acceleration but was likely just the more throttle response. It felt like I just tuned the RX300 up in 5 mins. It took the hills on like normal, (ie. like a champ, very little extra throttle necessary).So, then it made sense to me that he must have used the wrong octane. I sent him a text and sure enough he had used 89.

Mind you, before this day I haven't ever had anything lower than 91 in the RX300. Out of state I am sometimes forced to use 91 because that's the highest they offer. 91 doesn't have any effects like this on the RX300.

So, the point of this thread was to share my experience with using a lower octane. And, I wanted to hear if any of you have had any similar experiences or heard of something like this.

Please, once again do NOT turn this into a debate. Keep this thread as intellectual as possible.

 

I am now 3500 miles into my ownership of a 2001 RX300 with 138K and have always put "regular" octane gas in her. Getting 18.5mpg in the city and 23 on the highway and cannot complain about the performance. Am I missing something? Now, if you want to have an intellectual discussion about ethanol, I am in

 

My experience, not a debate.
My wife always puts in the cheapest gas (87) that she can find.
I always put in 93.
Neither of us have noticed any difference in performance.

BUT, she probably wouldn't notice if it was running on 5 cylinders, bless her heart, and I hardly ever drive it. So unless I drove it for a week on regular, all the way to empty, and then filled it with 93, I probably wouldn't notice the difference either. I usually fill up on a quarter of tank, so it's always a "mix" of 87/93 in there.

 

I have 4 daughters and know exactly what you mean! I am not sure if I need any more performance out of my daughter's RX300. It really runs great. I have read that premium gas is a higher quality product and may be better for the vehicle in the long run.

 

I guess I just have super power's then... LOL

I've just been around cars my entire life, and I get a feeling when something's up. I should probably admit myself into a asylum.

I probably wouldn't have noticed the difference in fuel if someone else filled it up with 93 after the tank of 89 and brought it back.

I didn't do anything in those 5 mins except fill the tank with 93. But, it was like an instant improvement. Maybe not instant, I think it took the car a few miles (about 2-3 miles) before it realized I put in different octane gas (93). After it did though, there was a difference.

 

Which fuel is better is not the right way to look at it. Each fuel is tweaked, the high octane is less prone to ignite prematurely and (less volatile) and this extra processing is passed on the customer. Actual cost difference may be much less than what the customers are charged. In the supply chain, the seller may even sell higher octane labelled as lower octane [they need to meet a minimum averaged out specification]. Due to higher price and octane numbering it has been assumed as "premium" .. meaning better. I treat them as different.

There is a loss of energy in pre-detonation, in fact it can produce force against the piston as it moves up. The dynamics change when the engine is at high rpm and the spark; to give time to spread the ignition; has to be advanced into the compression stroke.

Pre-ignition, depends upon the chamber environment (carbon deposits that can be glowing hot), and the octane difference. Some engines have the capability of changing the range of start of spark to handle lower octane and I think RX 300 can do it [Hyper in his OP stated premium only, and I did not want to nit-pick].

There can be carbon deposit and the engine could be loosing power due to pre-ignition. The deposits grow as the engine ages. [Seafoam any one?]. So the power loss can be real or it could be just perception.

I have used the higher octane to extend the need to change my knock sensors, till they quit on me. [at least one did]

Salim
[Hyper I tried my best not to make it an octane discussion, sorry if I failed].

 

I should probably stay out of this. When I lived at high altitude in Mexico City, I didn't need to use their 92 Octane (you can read all about the altitude and octane on the net), but the quality of the 92 (especially the lower sulfur ppm count compared to 87 regular) left me with 92 as the only choice.

However, since my car has been modified (and despite tests), it loves 93. I gave it some time with the 87 on two consecutive tank fulls. Even tried pulling the battery cables, nothing...it needed 93 to run right.

My neighbor across from me also has an RX300, but she drives it very basic and with 87 and that works fine for her.

 

Definitely notice the same difference you spoke of hypervish! In my 01,as well as my current 05. Both run/ran like $ hit on regular octane.

 

Haha, perfect response. I just didn't want the thread to become crazy if it was about which octane is better... LOL

 

Good! I thought I was going crazy for a minute there!

 

Yeah, I think for the day to day driver 87 is sufficient. The car runs fine, from what I've heard and there aren't many side effects.

But, for those that want or like the extra "power" 93 is a nice solution.

 

i agree 93 work better for me in my wife 99, i can tell the difference when i put gas in it and when she put gas in which is 87/89, the 93 performance is better. just my opin

 

Never noticed any obvious difference between 87 and 93. Perhaps there's something about your car that makes it more susceptible to detonation (carbon buildup?). The car may be sensing this and retarding the timing more than is usual?.

 

Maybe, but I highly doubt it.

I talked to my uncle today (he has a 99 RX300, 352k miles, original trans AWD). He told me he always uses 93 as well, and he's experienced what I did the other day. He occasionally does use 87 though.

 

I think 93 is better for me. I tried 87 and feel the differences.