You should take a picture or scan in the fuel information part of your manual. I would love to see it?

Toyota and Lexus cars/trucks are part of the SAE spec program. The SAE ratings take into account octane ratings, as well as other factors when a vehicle is rated. I believe engines must be hooked up to the drivetrain to achieve the ratings as well but I could be wrong. Before Toyota agreed to SAE ratings, they could use premium gas, achieve the HP rating, but they never needed to publish that the car needed premium for those ratings.

The best example I can give you:

2004 4Runner 4.7 235HP/320tq regular gas recommened (ratings achieved by using premium)
2007 LX470 4.7 235HP/320tq premium gas required (ratings achieved by using premium)

2007 Runner VVTi 4.7 260HP/306tq regular gas recommened (ratings achieved by using regular)
2007 LX470 VVTi 4.7 268HP/313tq premium gas required (ratings achieved by using premium)

The big difference is that the 07 4Runner under SAE specs, Toyota had to publish the real HP ratings under the fuel they recommended. In 04 customers could be told the vehicle makes 235HP while recommending regular, but the the ratings were achieved under premium fuel.

I highly doubt your IS350 is making the proper HP ratings Lexus advertised while using regular, I also think you won't scan or take pic of your manual to prove otherwise

 

Let's be clear. These are 2 very different statements. The manufacturer is recommending 91 for optimal performance (but is leaving unstated that if you don't mind less than optimal performance, then use something less, wink wink, nod nod). That is very different than "Regular per the manufacturer".

 

Huh? Can't you tell the difference when you fill up with regular vs. premium?

 

My IS and SC "require" premium, so premium is what they get. It helps if you don't have to pay for your own gasoline.

 

True. The RX actually list regular or premium while models like the GX require premium.

The end thing tho is if you look at similar motors in different platform mates they have different grades of fuel recommended. The regulars get 1-10 hp less, but also get 1-3 mpgs more. While the detergent case is always one thats helpful, certain stations already infuse all their tiers with a certain proportion of pea anyways. In addition to performance, lets be real, unless you can achieve that peak RPM range continuously that allows you to experience those additional 1-10 hp, I doubt a normal person would even notice. Maybe mentally but its not something I could tell the difference day 2 day. Note the above is for a car which has the option from the manual for both tiers of fuel. For those who use less then recommended, take this with a pinch of salt, since if your under warranty for certain makes, less then stellar fuel is always something a mfg can bring up as grounds for denial of warranty work in engine issues. After warranty its up to you.

 

I have always thought that the extra weight of the luxury features in a Lexus vs a Toyota is going to offset whether a person could tell or not. The extra MPG in a comparable Toyota I always thought was due to less weight vs a Lexus. For example, a Land Cruiser weights a little less than a LX570.

If anyone remembers the last gen ES350 had three HP ratings.

2007 280HP. Premium fuel required
2008 272HP Premium fuel required. SAE Certified
2010 268HP. Regular fuel recomm . SAE Certified



Premium fuel is very real thing. It would probably be reasonable to assume that those 2010 owners would achieve 272HP if they upped the fuel to premium.

 

+1.
It is to my knowledge that as was said here by others, that premium fuel does not give you more power, it simply allows your engine its maximum power because with 87, the knock sensors tell the ECU to retard timing to compensate for knock as required. Retarding timing loses a little power. I would rather run premium and do so because of this one thing.

 

You are right on with the octane/power issue. More octane in itself does not mean more power.....only if the engine's timing and/or compression ratio allows the safe use of it. Otherwise, except for (maybe) the added detergent issue, it does the engine no good to use premium.

Do you feel the few extra HP and torque with the premium is worth the extra cost? I'm not sure I agree. In my neck of the woods, at the pump, premium runs about 25% more than regular (even more at some stations).

 

All depends I guess. You could design an engine that runs on 87 octane. In the case of Toyota, it appears their cars run at a little higher spec on premium. I believe there are instances where a cars horsepower actually increased when fuel was downgraded from premium to regular. I believe the Corvette went up in 2006

 

I drive extra 2 miles just to get Shell 91 instead of Sams club 91, with 52 cents average more on the cost. I feel the difference, and with all the cars I have I don't use 87, period.

 

Another terribly misleading headline that will continue to confuse people and direct them to use the wrong gas. It should have said in the first sentence, "cars that require premium, should use premium. Cars that do not require premium, do not need premium." Period. The end. They way it's worded, and the way every Los Angeles newscast announced it, made it sound like putting premium in ANY vehicle is a waste. Same old misleading confusion since the beginning of time. So frustrating, we cannot progress as humans and report one particular story properly, in the name of bettering the public.

 

Very true, however how would an average ES driver notice the additional 4 hp when those are only available at @ 6200 rpm.

Maybe the same could be true that the HP curve would also reflect in the 0-3000RPM most drivers stay stuck in for extended periods of time but who knows, as the only published number we have is peak

 

Several manufacturers list the output of their engines on both regular and premium fuel. It makes sense and clears up uncertainty for buyers. Most of this is for turbo engines.

 

I had a 2010 ES, my 2010 required premium and they went to regular for 2011. When that happened I started using regular and felt no difference at all.

My 2013 GS had the disclaimer that it could run 87 if 91+ was not available. Tried that and the car definitely was not as responsive as it was with regular. More sluggish, hesitated off the line.

If one is driving an IS350 with regular fuel you're really not getting the full enjoyment out of that powertrain IMHO.

Never run anything but premium in the LS.

 

Can't say for sure, but one thing that may (?) have been a factor with your ES was that the 5Gen version had some problems with the engine/transmission ECU programming that delayed and/or messed up throttle and transmission response when accelerating from low speeds. That probably would have happened no matter what grade of gas you were using. A factory re-flash was supposed to help it, but, from what I understand, only had limited effectiveness.