PSA: Lexus ES350 Use Regular Gasoline Instead
 

I just discovered that the Lexus ES350 has the exact same engine as the Camry and Avalon and that the Camry has a 1mpg combined advantage over the ES350. The only difference between these two vehicles is that the ES350 calls for the usage of premium gasoline while the Camry calls for regular. There is a very slight performance decrease in using the Regular gasoline with the ES350 compared to using Premium gasoline as mentioned on the fuel door.

According to the New EPA mpg numbers from 2007-2010 MY.
V6 Camry:19/28/ [23 combined]
ES350: 19/27/ [22 combined]

To give you an idea of how small of a performance difference:
The ES350 with Premium is rated at 272hp at 6200rpm 254 lb-ft of torque at 4700rpm while the Camry with Regular is rated at 268hp @ 6200rpm with 248 lb-ft of torque at 4700rpm. They both have a compression ratio of 10.8:1.

Another example of this occurring is with the Toyota FJ Cruiser and Toyota Tundra with the 4L V6. It is another example of a Toyota Vehicle that claims it needs Premium but actually does just fine on Regular.
Straight from the Wiki:"The 1GR-FE is the 4.0 L version. Bore is 94 mm and stroke is 95 mm. Output is 236 hp (176 kW) at 5200 rpm with 266 lb?ft (361 N?m) of torque at 4000 rpm on 87 octane, and 239 hp (178 kW) at 5200 rpm with 278 lb?ft (377 N?m) at 3700 rpm on 91 octane."


So at the very least, going with regular gasoline with save you money both on fuel and should provide a slight increase in fuel economy. For those who are concerned that the Camry weighs less and therefore gets better fuel economy... The ES350 weighs 3580lbs while the Camry V6 XLE weighs 3516lbs

Are you sure they're tuned the same?

The idea is probably good, though; I suspect that most modern cars use less gas money on regular than premium even if they're designed for premium.

Seems to me that the mileage might drop slightly using regular. If the engine is running more spark advance, which it would using premium, it should get a little more power, and a little better fuel economy. The difference in miles per dollar spent on fuel might point toward using regular, if the loss of FE was only very minor.

That's the thing though, this is a case where I specifically can show a mileage improvement going with Regular vs. Premium.

My 2 volvos both call for 91 octane but do just fine on 87. There is a very slight FE advantage for 87 octane but the 91 produces more peak power. You'll never notice it unless you're flooring it. Octane requirement is dependent on a lot of factors like air temp, coolant temp and load. Most modern engine magement systems can adapt to low octane fuel without any FE penalty.

Yeah, its true that the two cars could have different timing tables in the computers. There might also be subtle differences in camshaft design or something else which isn't published.

However, I'd love for any premium car manufacturer to have a simple switch (performance / F E ) to switch between two timing tables, with the latter requiring high-octane fuel. I bet most people would use FE mode and use the low octane.

And since I'm on my soapbox, I think any car equipped with a gauge package should include a gauge that shows the amount of knock retard.

-BC

Plenty of cars have switches for economy vs. normal vs. power, which usually change transmission programming. People in general don't use them, are usually scared witless of the switch, freak out if they accidentally hit it, and resent the economy option.

A switching timing table is really not necessary. The knock sensors on these engines function in closed feedback loop to advance timing beyond what the timing table sets until its running on the verge of knock all the time. You and I can't hear it but the knock sensor sure can. The closed loop system can be extremely aggressive and adapt to fuel octane on the fly. BMW and a few other manufactueres have started measuring the resistance between the spark plug electrodes in real time to measure the peak pressure and timing inside the cylinder. It then adjusts timing and fuel mixture for each cylinder individually for maximum performance and fuel economy.

You are correct tjts, a modern engine with a knocksensor automatically adapts to the octane rate and delivers always full power when flooring it.
On half load, it will always be as economical as possible. In my understanding, it's because of the knock sensor there IS a difference in performance. There's no difference possible without knocksensor.
Without knocksensor the 'mapping' is always adapted to the minimum octane requirement, and riding on a higher octane rate does not help you safe fuel or deliver more power.
Changing to a higher octane rate without knocksensor can help in situations where there's a lot of carbon in the cylinderhead, tuned engines (higher endcompression), changed ignition timing...

Just thought I would throw some real world data into the mix here.

Through dynamometer testing at work we were able to determine that using regular fuel in an Acura 3.5L that requires premium will increase fuel economy but will lower performance.