2008/9 Highlander Engine Specs

Gasoline engine -- 3.5-liter double overhead cam (DOHC) 24-valve dual independent VVT-i V6; 270 hp @ 6200 rpm, 248 lb.-ft. @ 4700 rpm

2008/9 RX350 Engine Specs

Underneath the hood of the RX is a 24-valve, DOHC, 3.5-liter V6 engine which produces a scenery-blurring 270 horsepower [1] at 6,200 rpm [1] and 251 pound-feet of torque at 4,700 rpm

The RX has 3 extra ft lbs of torque and requires Premium Fuel, the Highlander has the same HP and 3 less ft lbs and only requires Regular Fuel, so why would Lexus require premium just for 3 ft lbs? and does the RX just make a little less torque if you run it on regular??

Maybe Exxon Mobil is just paying them to tell us to run Premium!

 

You can run regular without any problems. I have run regular in my 570 and noticed no difference.

 

Just curious why Lexus says it is required 91 or higher, but Toyota doesn't, there seems to be absolutely no need for Premium, so why does the manual require it?

 

It is hard to tell why but my guess would be that you would need to see a full range Dyno print out from both cars. A full range print out you would see the HP and Torque at all RPM's not just peak. This most likely would show higher HP at lower RPM on the RX which should give you better drive-ability than the Highlander.
I guess we need some one to race a highlander and an RX to see if there is a difference from start to finish.
Jeff

 

I think the engine can run on either, just as mentioned above a hp difference. On regular the car feels somewhat muddy it could be my imagination. While on premium it feels more responsive. Who really know, I guess someone should put it on a dyno. I would be interested too.

 

The requirement for 91 octane or higher has caused us concern with our new 2009 RX350 also. The Lexus manual is quite clear about requiring 91 or higher octane. However, no one (including the dealer) seems to take Lexus seriously about this. I recognize that lower octane gasoline will cause a performance hit as the knock sensor retards the spark to prevent detonation. However, I am concerned that even with a knock sensor, the risk of engine damage increases, maybe unacceptably.

Twenty years ago I bought a new BMW E30 M3. It had a four cylinder 192 Hp 2.3 liter engine. The compression ratio was 10.5:1. BMW was very explicit about using 92+ octane even though the M3 also had computers and knock sensors. At that time, I was dating my wife. She took the M3 one day and I remember telling her to make sure she filled it with only "premium" gasoline. She indeed did fill it with "premium", the 89 octane "Premium", instead of the 93 octane "Premium Plus" at the adjacent pump. I called BMW NA. They very strongly advised to not not drive the car but have it towed to a shop that would drain the tank. (I did drive it, very slowly and easily about 10 miles to a shop to drain the tank, with no apparent harm). Here is the point. This car had only a 10.5:1 compression ratio, less than the 10.8:1 of the RX350. The engine ECU computers were very sophisticated even twenty years ago so I am skeptical about the safety of anything but 91+ octane in our RX350.

 

I would re-read the owner's manual with regard to minimum octane. I am relying on memory here but I believe the discussion of premium fuel is based on achieving maximum horsepower. I also think that the discussion in the manual says something about the vehicle being perfectly functional with less than premium. In the case of my BMW, it states something like that but also states to not go lower than XX octane rating, maybe 89?. Our 2005 RX330 has run quite nicely on regular grade fuel since new.

Gary

 

its not necessary to run it on premium.

half of it is better horsepower and torque numbers
the other half is the concept that a premium branded car deserves premium grade gas. its an image thing more than anything. plus, it allows a marginal seperation between toyo products and lexus products

 

on the 04 I am pretty sure it says recomend. and if you got to the EPA site I think the cost of fuel is for regular gas in the RX. On the 3.3 and 3.5 aren't they just Toyota engines? Because my dads Toyota Van engine looks exactly the same as my Lexus car engine. So I would say no problem

 

Lexus wants you to believe you have a premium auto. They have to help you justify the $10K premium over the Highlander, same as Chevy and Buick. The engine is not a performance engine and is identical to the Toyota 3.5. The Toyota is rated on regular fuel the Lexus on premium. The Toy/Lex engine does not even require a synthetic oil!!!

 

I know there have been many discussions on premium vs regular and I too was wondering what the difference could be between the highlander and the rx. Well here's what I noticed when we were living in Charlotte NC during the gas shortage created by the hurricane that hit the Houston in Sep of 08.
For a period of almost 4 weeks, we were forced to run regular in the rx350.
According to the engine computer, my wife was getting 12.5 to 13.5mpg with regular vs the typical 15.5 to 16.5 with premuim. Her driving style is basically short trips on suburban streets. When I noticed the big drop in mpg using regular, it did not take me long to realize that it was actually cheaper to use premium instead of regular given the car just went further on a tank of premium gas.

So all I can say is go ahead and try regular for a month and see what your mpg's are and then do the math to see if premium is actually chaeper for your own particular driving style.

 

Many owners have been getting mix result as far as MPG is concerned between the 2 grades. I myself have use regular many times and notice maybe a 1/2 MPG diff at most when I run on 3 or 4 tank full of 87 octane. I do notice a slight difference in accelaration also.

 

Another reason for difference in torque between Highlander vs RX may be vehicle weight.

 

Torque has nothing to do with the vehicle's weight.

 

I try to maintain a 91 Octane balance in my RX350. In my area there are 3 main grades of gas, 87,89 and 93. I keep tract of my fill ups and try to alternate between 89 and 93 octane when my fuel guage is at the halfway mark. In situations where this is not possible I just put in the premium 93 octane.