igzy

I have not tried running the regular to see if there is a drop in mpg. I currently average 28-29 mpg on my 420-mile weekly commute. In Ontario, the difference between regular and premium is $0.14-$0.16 per liter (est. $0.60 per gallon). For me, this translates to $8 per week difference if I was fill up on premium vs regular, so about $35 a month, or 10% of monthly gas bill. The real trial would be to see if the mpg would drop with regular and by what % (more or less than 10%) and if the switch to reg would be worth it...

With winter weather this trial would be tricky as I am noticing that mpg is dropping as the outside temp is. In the summer I was getting 30-32 mpg, now I am in 28-29 mpg range, so getting a feel if regular is same or worse could be hard to tell, or if it is cold weather related...

garsarno

Used premium in my 2007 and regular in my 2011. I saw no difference in performance or fuel economy.

Rogarven

Thank you for this thread. I am getting a' 09 es 350 today and the owner claims he always put premium in the tank. There is a 20-30 cent difference in price but we drive very little now with us both being retired. I just remember the days when I had a '73 Pontiac Lemans with a 400 cc V8 that would ping strongly if we didn't put high test in it, especially in CAL Also,'75 Volvo would ping as well. I am driving my mom's 05 Deville now and have no problems with regular with the Northstar V8. I just don't want to be "penny -wise and pound foolish". Thanks again.

lgb0250

You'll be perfectly fine using nothing but 87 octane. We've used nothing but since the day of purchase and have always averaged over 28 mpg. Enjoy your new ride.

rx300mm

I have been using 87 octane in my 2007ES since 2009, no issues so far. Love the smooth ride.

christcorp

I have found that each person really needs to try for themselves. Each vehicle is different. It won't hurt anything or break anyone's wallet to do a couple tanks in a row of each grade. You might notice a difference and youight not. I live in high altitude, so we also have 85 octain. It equates to 87 at lower altitude. My daughter bought a new suburu outback and she tried 85, 87, 89, and 91. Both 85 and 87 made OK gas mileage but she noticed some hesitation and what she said weird noise while warming up. She tried 89 and 91 and noticed a couple mpg improvement and no noise. She is staying with 91 because its only about $0.10 a gallon more. ($1.50 a tank).

I found no difference at all in 87, ,89, or 91. So I stay with 91 because again, its only $0.10 more per gallon. Or basically $1.80 per tank). Its not a matter of harming the engine. You buy a nice car like a lexus, you need to find out what YOUR car likes. Not what someone else's car likes.

rickster9

Are you using the computer to calculate your MPG? When I bought my 2010 350 there were 2 of them on the lot and both computers claimed they were getting 13 mpg and mine still claims 13 mpg....

jcat_350

This is the basic principle here.

Does anyone really think they're smarter than the Lexus engineers who decided that the car needed that sticker saying to put premium gas in? Not to say that I don't think carmakers are in bed with fuel companies, but I don't think there's really much benefit for them to build a car and tune it for one grade of fuel over the other.

Even if you filled up twice a week all year long, that would account for 104 tanks at an additional $1.50 per tank, or $156 per year. The car WILL get better mileage and have more power on higher octane fuel, simple fact. Is it really worth it to rob the car of it's potential to save pennies per day? I personally don't think so.

Then accounting for the fact that there is a possibility, however remote, that the car could start pinging on lower octane fuel which can cause engine problems (detonation burns up pistons, inefficient ignition leads to a constant rich condition which over time eats piston rings etc.), it seems even more silly.

Also, don't go by the computer. Every single one in every car I've ever had has been over by 2mpg or so, at least. That's why they're commonly referred to as the 'lie-o-meter'. Calculate it out by hand. Fill to the click, reset the trip, then when you fill next divide miles driven by gallons filled, and there's your TRUE mpg.

christcorp

JCat. Normally, I would agree totally with your last post about using what the manufacturer recommends. Except in this case. The reason being; is that the Lexus and the camry/avalon v6 have the exact same engine; and the camry/avalon recommends using 87 octane and the lexus recommends 91. (At least in the 07-09 year range). Of course the lexus boasts a few more HP over the v6 camry/avalon, and that may be the extra couple octane points.

Point is; they are identical engines, down the plastic covers and one recommends 87 and the other recommends 91. No logic to this.

Rogarven

I would agree with the trip calculator. Unless it is reset every time, you are not going to get an accurate reading. We always, write down miles driven and gallons used. It works every time

kewl

The general opinion in this thread seems to be that pre-2011 ES350s 'required' premium fuel be used. I have an 07 and I cannot find in any Lexus documentation the 'requirement' to use premium fuel. Recommended, yes, but even the manual states regular is okay with some performance impacts to be expected.

liquidz

There car's trip computer has two values: 1) Overall average MPG that does not reset. This only resets when the car battery is removed and the ECU looses charge. 2) There's an Tank MPG (Canadian version has it), that resets most likely based on the fact that the gas door was opened or cap was removed. This number is a little more accurate but from hand calculations I would still get higher values that the trip computer number. So basically take any number on MPG from the car with a grain of salt.

jcat_350

You already pointed it out. The Lexus shows more power and torque than the Camry. These are just peak numbers, though, so it doesn't tell the whole story. To understand it, you'd need to see dyno charts side by side of each car running on the respective fuels, and examine area under the curve. This is to say that while the engines are identical, and weight is identical, the ES will be quicker across the board due to making more efficient use of it's power output from low RPM to high, not just in peak numbers. This is a function of VVTi being adjusted to take maximum advantage of the premium fuel by advancing the timing. I'd bet that the Camry could adjust from 87 to 89 pretty easily, but the upper threshold likely wouldn't be able to take full advantage of premium fuel.

If you ever want some insight into how VVTi really works and how it affects the tuning of your ECU, head into the 2GS forum and read up on some NA-T builds and what a pain in the *** it is to tune them with a piggyback FIC!

Well it's not quite that black and white. The computer has a lot of variables in it, for example...when you're idling, how can it take into account the mpg when there are no miles being traveled but only gallons being used? It can't, so it uses the stated gallon per hour (or liter per hour I'd imagine) figure for the fuel pump, based upon the amount of time you've been idling, then determining how much fuel you've used, and estimating how many miles that would have been. The only 100% accurate, surefire way to calculate your fuel mileage is to fill up to the same point every single time, and reset the tripometer in between. Then you get a true calculation of the miles you've driven vs. the gallons of fuel used.

LexBob2

I've felt all along after buying an early '07 ES350 in May '06, that either premium or regular unleaded is fine. Whatever you are comfortable with. At launch, Lexus said premium was recommended to achieve the advertised horsepower (272).

As mentioned, Toyota uses the same engine in Camry, Avalon, Venza, RAV4, Sienna and Highlander with regular recommended. Those models were rated at 268-270 hp. and the ES on premium was rated at 272 (giving it an image bump over Toyota models IMO). These days on regular the ES is rated at 268.

EPA estimates are the same on regular (2011-2012) or premium (2007-2010). You can't go wrong either way.

greenchile

I've always speculated on how the car computers calculate the fuel economy. I have not done a search nor do I have firsthand knowledge but I think it probably does it by counting the number of times each injector opens and the duration it was open. I seriously doubt there is any sort of flow meter that measures the exact volume of fuel consumed. But I suspect that you can determine how much fuel was consumed with pretty high accuracy by looking at injector cycles. Due to the precise metering of fuel required for an efficient combustion cycle, the need for a consistent fuel pressure, the injector open time would give the best number of volume of fuel used. Having said that, the lie-o-meters on my 2011 Sonata was always high by a good 2 mpg and the ES350 seems to be high by about 1 mpg, when compared to calculating my mpg manually.