Lots of good facts, some opinons, some anecdotal evidence but, imo, some of the opinions are substantiated by fact.

Here is my story:
2005 RX330 with 42000 miles. Regular gas after the first year. No knocking, pinging, or hesitation. Since this car is driven by my wife (she is a granny and drives like one) there isn't any noticable difference in performance. When I drive the car, I don't notice anything out of the ordinary.

My thoughts on regular are that the engine is a Toyota engine designed to run on regular with an upgraded cam to get more power. Of course, most manufacturers that want to play "the my car has more horsepower than your car" game will specify premium gas. Most (all?) cars that require premium gas will run just fine on regular. That isn't my opinion but the views of the likes of Consumer Reports, the manufacturers themselves, and other testing agencies. Of course, certain brands absolutely require premium. I note that the manufacturer usually specifies "for maximum performance" or some similar statement and usually includes the caveat about pinging or detonation. I guess that if you have a heavy foot on acceleration, live at a higher altitude or routinely load up the back end that you may need premium. I don't.

Fwiw, my 14 year old Acura has run the last 13 years just fine of regular as does my one year BMW. I am acutely aware of pinging and haven't heard it in any car yet.

So, drive it with a full tank of regular and pay attention. If you get pinging, go to mid grade and so forth.

Gary

 

most knock sensors are so quick to react along with the ecu that one will never hear pinging/knock/preignition/detonation. they are that fast. especially if after one episode of knock, the ecu has already pulled timing. as long as it never gets a tank of 91+ and allowed to revert to factory spec timing, the timing will remain retarded, and the driver will never know the difference.

 

Gary,My belief is if it is required,and states on the fuel door premium or 91 octane only,then you should use it.If it states premium recommended I really don`t think their should be any problem.Basically they recommend premium so you get the rated hp,and fuel millage out of the engine.

 

Agreed,your just not going to get the full potential out of the motor.And some people such as myself like all the squirrels that little 1mzfe can muster.

 

I believe the 3MZ-FE is in:

• 2004-2006 Toyota Camry SE V6
• 2004- Toyota Camry Solara
• 2004-2006 Toyota Sienna
• 2003-2007 Toyota Highlander
• 2005- Toyota Highlander Hybrid
• 2003-2006 Lexus RX 330
• 2006- Lexus RX 400h
• 2004-2006 Lexus ES 330
• 2006- Mitsuoka Orochi

The 1MZ-FE is in:

• 1994–2003 Toyota Camry
• 1999–2003 Toyota Camry Solara
• 1994-2003 Lexus ES 300 & Toyota Windom (Japanese domestic market)
• 1995-2004 Toyota Avalon & 2000 Toyota Pronard (Avalon for Japanese domestic market)
• 1997 Lexus RX300 & Toyota Harrier (Japanese domestic market)
• 2000 Toyota Estima (Japanese domestic market)
• 1998-2000 Toyota Sienna

wt-i version:

1997-2004 Toyota Avalon
2001-2003 Toyota Highlander/Kluger
2003-2006 Toyota Camry
2001-2003 Toyota Sienna
2002 Toyota Alphard (Japanese domestic market)
1999-2001 Lexus ES 300

source: http://en.wikipedia.org/wiki/Toyota_MZ_engine

 

Talk about people missing the whole point of the OP's article. This thread isn't about whether your car will run on regular, it points out that you are very likely paying more per mile by using regular than if you used premium. You are also giving up power in the process, and the extra engine cleaning detergents in premium too.

 

I agree with you their too,The thing that concerns me a little right now is,with fuel prices being the way they are,Premium unleaded is not selling nearly as quickly as the regular is.Back a few years ago it made up almost 40% of the gasoline sales,now its like 8 or 10%.That tells me it is sitting around alot longer in the underground tanks,and todays fuel does not store well at all.So,with that said,are we gaining anything by using fuel that is sitting around alot longer?In other words,fresh 87 or more stale 92/93?That is my question.

 

For clarity sake, the engine in the current RX350/ES350/Highlander/Camry is a 2GR-FE.

 

If the Camry and Sienna have the same engine why don't the Toyotas need premium fuel?

 

It sounds like we are not converging on an answer, and Lexus is not going to give us one. Is there some way the forum members can do some experimenting and figure things out. For instance is there some way we can run tankfuls of 91, 89, and then 87 octane and see what is going on with knocking and spark advance? Like, can we use the OBD port to read spark advance settings in real time, or read the number of knock events?

My driving is a little sporadically mixed between highway and city at different times, so I can not easily compare apples to apples with a mileage measurement (odometer/gallons). Maybe some forum member that does all highway driving can try the three tankfuls and report on the mileage performance.

 

Clearly there are different versions of the same basic engine. See the specs here:

2007 Toyota Avalon XL Sedan
- 3,456 cc 3.5 liters V 6 front engine with 94 mm bore, 83 mm stroke, 10.8 compression ratio, double overhead cam, variable valve timing/camshaft and four valves per cylinder
- Unleaded fuel 87
- Power: 200 kW, 268 HP SAE @ 6,200 rpm; 248 ft lb , 336 Nm @ 4,700 rpm

2007 Lexus IS350 Base Sedan
- 3,456 cc 3.5 liters V 6 front engine with 94 mm bore, 83 mm stroke, 11.8 compression ratio, double overhead cam, variable valve timing/camshaft and four valves per cylinder
- Premium unleaded fuel 91
- Power: 228 kW, 306 HP SAE @ 6,400 rpm; 277 ft lb , 376 Nm @ 4,800 rpm


So while these two vehicles use the same basic engine they have different compression ratios and much different power output. The bore and stroke are identical which suggests different pistons or heads and cams.

 

Just stumbled on this at Edmunds.com sourced from from the Lexus College System <www.lexuscollege.com>

 

I've been running 87 in my new 2008 RX 350 and haven't noticed any knocking. (Years ago my first car was a hand-me-down 70's Pontiac with a V8 that was supposed to take premium and knocked like mad on acceleration using regular so I do recall what knocking was like.) If the sensors and computer have made adjustments on account of the gas then they are doing a great job as performance is fine and I sure don't see how it could be hurting itself. I am in compliance with the owner's manual which states that 87 *may* be used.

I've been measuring MPG on virtually every fill-up using the odometer and pump readings, not the built-in computer. I fill til the filler spout is full so as to eliminate that variable. I've been getting about 19-20 MPG but as much as 22 if mostly highway driving. I'm not a huge leadfoot on acceleration but definitely no slouch either and open expressway driving is at speeds which are...um..."up there."

On my last fillup I went with 91. I've noticed no improvement in performance. I'll be curious if the MPG goes up but even if it goes up a tick I doubt it's going to be worth the expense.

If it's true that there are better detergents and so forth in full premium then that might be reason to buy a tank every so often. But otherwise if performance is fine at 87 and it's not hurting anything then with no economic justification to go to higher octane then I would just stick with 87.

 

Looks like that "lexus college" needs some remedial education! There is absolutely no difference in the energy content of 87 vs 91 octane gas! The only difference is that it is harder to ignite 91 octane gas by diesel effect. Love that pseudo-science, though!

 

[QUOTE=filmteknik;3761942]
On my last fillup I went with 91. I've noticed no improvement in performance. I'll be curious if the MPG goes up but even if it goes up a tick I doubt it's going to be worth the expense.

Remember that if the computer has retarded your timing to compensate for perceived knock, it will keep the retarded setting for a period to protect the engine. It will take several tanks of the higher octane fuel for the computer to reset to the factory programed timing. On a single tank of 91 octane, the timing was likely still retarded so there would be no improvement. The retarded timing is what causes the reduced engine efficiency which shows up as less power and poorer gas mileage.
Steve