igzy

+1

This is the reason it was originally programmed for premium gas and to get higher HP rating. For most part, most drivers will not notice this subtle difference when using regular vs premium gas...

And yes, the ECU will change the timing based on gas used. Some studies also showed better mpg when using premium where default timing is advanced. So it comes to price and mpg % difference, i.e. if the savings on regular are better than offset by the mpg decrease...

geopig

I thought I would provide some anecdotal evidence regarding getting better fuel efficiency with premium since I have just finished testing for myself the difference. Last summer my family moved back to Canada and are now closer to family (i.e., easy driving distance to visit relatives). The drive is almost exactly 550 km (340 miles) and we have done it now close to 18 times (18 one way drives, so a total of 9 round trips) in the summer/warm months (I'm excluding the winter months where different fuel and tires are used). It includes nice stretches of open highway where one can easily cruise at 120-125 km/hr (75-88 mph) as well as traffic situations (driving through Toronto, ON) where some stop and go is encountered. I typically choose times to minimize the traffic issues so most of the distance is at highway speeds. I switched to using 87 octane a few years ago since gas was much cheaper to do so even though I was pretty sure that fuel efficiency changed. I'm not going to comment on power at all since I did not notice any difference in performance between premium and regular.

So on to my test. I was curious about the difference since I recall that before switching I thought I was getting better fuel efficiency. So for these 550 km trips I continued using 87 octane last summer/fall and for the first 2 trips (full round trip) this summer. I was getting 8.2-8.4 liters/100 km (28-28.5 mpg) each time using 87 octane. The last 4 trips (2 round trips within 2 weeks of each other) I switched to premium (91 octane) and kept using 91 octane between the trips to make sure engine mapping did not change. The first trip the fuel efficiency did not change. The second trip on premium the fuel efficiency improved to 7.8 L/100 km (30 mpg). I'm guessing this is when the engine mapping was changed or changing (?). But the last two trips the fuel efficiency has been at a solid 7.1 L/100 km (33 mpg). So that is a fairly substantial difference in my opinion.

Anyhow, just thought I would share this information for those interested. Of course if the cost of premium is so much higher that the 4-5 mpg savings are moot then continue using regular. To each their own. I certainly did not notice any performance issues with my original switch to regular nor the recent switch back to premium. But I do like the fact that on premium I'm getting better fuel efficiency.

igzy

I too am in Canada and MPG improvement with premium gas didn't justify the cost of premium for me as I got less than 10% MPG improvement vs 15% price up for premium.

Performance: most won't notice the difference in timing as it is noticeable at WOT and throttle response at high speeds. On 270-ish HP engine that is really hard to detect on most daily drives. I notice it when I merge the hwy, one of my on-ramps is a tight loop followed by uphill merge onto hwy, so I have to go WOT to safely merge the traffic and I notice the difference only there when I have regular in it...

jkayca

Is there a difference in how clean the fuel burns? My brother insists on putting 91 octane into his car to reduce carbon build up. Is this for real?

Paul3637

**********
Although I drive a 2009 Camry V6, the engine is the same as the ES. (I joined Club Lexus because my wife used to drive an ES.). When gas was $4 a gallon, premium fuel in both Kansas (where I used to live) and Florida (where I now live) was 20 cents a gallon more .... or about 5%. For the first 50,000 miles or so, my car got nothing but premium gas. As gas prices dropped, the spread in Florida became 50 cents a gallon. I switched to regular and there was an immediate drop in gas mileage of 10% but no detectible difference in performance. All I'm doing is confirming what you and others are saying since I have seen others say there is no difference in gas mileage. Maybe it's because it takes more than one tank of premium to get an advance in timing from the ECU.

Also, the car now has 100,000+ miles on it now and oil consumption is still zero (I use Mobil 1 synthetic 5W30 changed every 7,500 miles) and the engine purrs like a kitten so I doubt using regular has any adverse effect on engine wear.

mlacomb

Given miles per gallon of 28 @ 87 and 30 @ 91+, the sheet I just put together states that the cost per mile differential makes sense if the difference between 87 and 91 is 10 cents or less with base 87 at 2$ a gallon, and 30 cents or less with base 87 at 5$ a gallon.

AbeerAH

Back in August 2017, I bought a used 2007 Lexus ES350 and I love it Since I bought it, I have been using unleaded plus and the prices are a bit steep these days, so I am wondering if shifting to a lower-grade unleaded fuel would impact the car's performance? I tried locating a manual for 2007 but was unsuccessful. Any feedback from Lexus-experts would be highly appreciated!! Thank you! Abeer

jagtoes

This has been discussed by many on the form and if you want to read about different opinions please use the search function. Now the short answer is , no it doesn't make any noticeable difference. But if you want to understand the difference there is a 4 HP difference between PLUS vs Reg. Also mileage isn't any difference so feel free to change.

ESh

Why people say it will lose 4 hp on 87?

jagtoes

People didn't say it was Lexus that stated the difference. Those with the early cars can look at there OM and under spec's that will see 272 HP on premium fuel. Somewhere around the 2010 +/- MY the spec changed to 268 HP on regular fuel. Same engine without any internal changes. Same for the toyota engines.

kodavis

The owner's manual recommends 91 octane or greater. I bought my 08 ES350 in August 2017 as well and I've been using 89 mid-grade in it since I bought it. It runs great. I have filled up on 93 premium a few times and I didn't notice any differences in fuel economy or performance. If you use a lower grade fuel, the computer should compensate for it.

LexBob2

I bought a 2007 ES350 just as they came out in late April 2006. There was a lot of discussion on regular vs. premium. At the time, every Toyota product with the same engine (Camry, Avalon, Venza, Sienna, Highlander) were recommending regular and showing the 268 hp vs. the ES350 at 275 on premium. You can't go wrong with either grade. Strictly personal choice IMO.

ESh

RXGS

iTrader: (2)

Friend just traded in his 2010 RX350 (same engine) after running regular nearly its entire life. He did say towards the end it started pinging, but would go away when he put 93 in it. So i guess you can, but after an extended period of time, something may happen.

Htony

Timing has to be retarded by ECU to prevent knocking. Common knowledge.
For maximum designed performance use gas mentioned on owner's manual.