For the next 30 days, I'm going to run 92 Octane or better. I've run 87 Octane almost exclusively since I bought my RX. I begin with a 900 mile road trip tomorrow and will report my findings as I generate them.

I filled up with 93 Octane this evening and had about 2 gallons of 87 left in the tank, so currently my Octane rating is approx. 92.3.

I plan to add nothing but 93 for the next month. We'll see.

 

So Daddy-O tell us what you see

 

I suspect you won't see too much difference. Since I hadn't read my wife's manual, I assumed the RX used "premium" gas (93 octane around here) from day 1 till about 2 years ago. I noticed no significant difference at switchover; because we were traveling, I was driving most of the time through the first two tankfuls of 87, so I had back to back comparisons. Didn't try to directly compare mileage though. Wifey is, of course, happier since she's saving about 0.20 /gal.

But I'm embarrassed that I hadn't read the manual, even though it's HER car.

 

mooretorque,

I expect my experience will be similar.

It's easy gather empirical mileage data...My butt-dyno will, of course, be more subjective. I bought the RX partially based on the fact that it ran on 87 Octane. Some talk about giving it the "good stuff" or "spoiling" it...well, that just never made sense to me.

Some contend that over the course of a year, the savings may be minimal ($4/fill-up), but why spend money unnecessarily? For me, it's more than that. It's about the right tool for the job.

I live on the coastal plane of NC. Land doesn't get much flatter. 90% of my driving is here. Regular gas is perfect. Lexus says 91 Octane or better for "improved vehicle performance".

But, hey...If there's a significant performance change, I'll continue to buy 91 Octane or better. That would have to mean noticeable butt-dyno results and a 15% gain in mileage (to offset the price).

 

Amen.

 

Early results...

1st Tank: 100% highway miles 27.1 MPG. Last time I drove this route, I got 26.9. I managed to draft behind a Honda Odyssey van for 70-80 miles. Mmm...cruise control.

2nd Tank: 70% SuperHwy/30% City 23.1 MPG
That's the mileage I would usually get.

Butt dyno: This morning I had to get around a Tractor-Trailer and stomped on the gas. Whew...My RX jumped like it was bit-slapped. It did happen at a 25MPH drift, however...The auto downshift alone could have accounted for this. I was gone in a flash.

So, to conclude: No noticeable real difference in mileage/performance and I've spent $7.00 more on gasoline.

More to come.

 

Well, this last tank was 100% city driving. I filled up on 10/14...9 days ago. Stop and go, stop and go. I doubt ever drove more than 5 miles without stopping. I also stomped on it more than a few times, trying to feel any butt-dyno results.

17.4 mpg...The absolute worst mileage I've ever gotten in this vehicle.

I've been pushing it hard, trying to feel the difference that 93 Octane fuel provides...I have to say that I'm not feeling it, y'all. My RX was pretty peppy with 87 Octane and if there's a difference with Premium fuel, it's lost on me.

Total additional cost since 10/12: $10.60
11 days down. 19 to go.

Oooh, and I got my $9 oil change today, too. Love that Toyota Express Lube!

 

Hey PDaddy-O, You'd take a supermodel out to Burger King!



I'm just giving you a hard time. To each his own. I choose to put the good stuff in mine... it seems to run better here in Denver. Sometimes I buy 89, but I usually get 91... The altitude seems to make a huge difference in how my RX rides compared to yours...

Hando

 

I think I may tend to agree with handogen.

I've had my RX for 3 years now and I live in the northeast. I go skiing A LOT and I carry a lot of stuff with me (not to mention some of my overweight friends).

I've found that 91+ octane gas does make a difference. I cant really tell most of the time when Im driving on flat ground, but when Im loaded up and driving up the side of a mountain, I can really feel the difference between 87 octane and 91+ octane. The RX just seems to not struggle as much uphill. You press on the gas and it climbs. With 87 octane i have to press harder on the gas, the engine growls more and i dont get to the slopes as fast. My girlfriend noticed the less than optimal umph the car had with 87 octane too.

Just my opinon. Dunno if Im just overly sensative or believing what I want to believe....

 

Finished another tank...

20.8 MPG: 70/30 Hwy/City driving.
The numbers indicate that my mileage is down during this experiment. I'm as concious of my right foot and the tach as I ever was.

Butt-dyno is inconclusive. Perhaps performance is better and I've habituated. Perhaps the difference is so slight that I can't feel it. Perhaps there is no difference.

If there's an actual performance gain, I'll know when I switch back to 87 Octane. I should feel the difference.

Total additional cost since 10/12: $14.40
21 days down
9 to go

 

27.1 mpg, 26.9 mpg???? how do you manage to exceed the vehicle Hwy estimates by 22 - 23 percent? I need to start doing whatever you are doing. Havent done better than 19.2, according to computer anyway here in NJ with a 50/50 city/hwy run.

 

The highway estimates of 23/24 mpg is taken as a average from a range of mpg that can be achieved with highway driving - depending on your speed.

At a speed of about 65mph you can get just over 26mpg with a FWD RX. Just reset your AVG MPG before you get on the highway and you'll see. I usually get 26.2 mpg going back and forth from home: 2 hour drive and speeds vary from 60-75mph. Traffic varying from medium to heavy.

 

I knew i left a detail out.... I have the AWD. But will try resetting just prior to getting on the highway.

 

Burned another tank on Friday and filled up again. 100% city driving and 17.4 MPG again. Another worst mileage total. I am not understanding why my city mileage is so bad since this experiment began.

Monday, I'll be driving 200+ miles and finishing the last tank of 93 Octane gas. I will burn it as close to empty as possible and fill it with 87 Octane.

Total additional cost since 10/12: $18.35
28 days down
2 to go

 

Finished another tank. 80/20 Hwy/City...23.4PG.

I ran the tank as low as I could go and filled it with 19.3 gal of
87 Octane gas.


30 days cost an additional $18.35US.
That's $223.26/year.
$893 over the next 4 years.

Did I see any improvement in mileage?
No. There was actually a decrease in city mileage.

Did I see any improvement in performance?
No. My RX was running great on 87 Octane. If there was a
difference in performance, I could not feel it. Now that I've
switched back to 87, I'll have the opportunity to note any
lag in performance.

More to come.