I think what I am getting out of this thread is this:

If I expect to use my engine to best capacity (i.e. heavy loads, towing, street racing), I am better of using Premium for preformance and avoid pinging. BTW, Any chemists out there who want to comment on this, regarding free carbon chains in the molecule derived by the catalyzing of the fuel during refinement.

If I would like to economize a bit in an area that has more expensive gasoline (i.e. $2.40 g/reg vs. $2.60 g/prem) I can use the lesser qualified fuel without fear of me coating my engine with some permanent goo.
--------- what my rational is for using the lesser grade -------
In the long run, I will not be damaging my engine, but I may slightly increase the carbon buildup in my engine with the lesser fuel and lower detergent concentration. (perhaps running a cleaning solution around every oil change time will minimize this situation.)

If you put 10K/yr and chose which ever fuel you desire ( about 16.5mpg avg - at around $0.20/gal difference between the grades) a year on your car that would translate to around $121/yr difference.

What I have noticed, is no one is saying you will DAMAGE your engine if you chose the lesser grade. You will not realize the full capacity of your truck's preformance. It just depends on which you desire more. The need for speed/performance or the need for greater distance using less money.

Personally, I have noticed a slight difference between the grades (btw I use Chevron). But, I have already noticed that there is less casual driving in my area on the weekends. This could be indicative of what other people think as well.

 

Small world, I live in The Palace Resort half the year

 

if lexus owners want to use regular after purchasing an almost 50K vehicle, why not sell it and buy a different branded truck that is made to run optimally on regular, and also cost less in terms of purchase price ?
i knew some s class owners who would use regular gasoline for their cars and i was very suprised. i then asked some of the owners for the reason and all of their replies were" it's a leased car, we could care less". so if that's the viewpoint of this thread then i can understand somehow, but if this thread is geared towards the 'owners' of the vehicles who are talking of keeping it for 100k range, then....

 

The GX's engine was designed to run on regular grade gas. That's what the Owner's Manual says. For me, it's not a matter of money, it's a matter of following the manufacturer's recommendation. I had a GS400 and the manual said to use premium grade, so that's what I used. I tried running 89 octane in the ES330 when it was new and then switched to regular about nine months later and the engine ran just a well and got better gas mileage. The manual was right

 

The POINT is that the GX is DESIGNED to run on regular. You can put higher grade in if you like. But as these threads are showing, you sometimes get worse fuel economy. There is no "build up" with modern fuels so that arguement is void. Run premium if you like. Some of us are able to afford these cars because we realize that there is no point in wasting money (even on a $50K car). Now, if this were a $120K performance car that REQUIRED premium, I don't think there is a person in here that would not put it in. In this case though, there is no point putting premium into a truck that gets better fuel economy with regular IMHO. Granted, you may get a little more "performance" out of the premium, but it "apparently" comes at the cost of worse fuel economy.

 

something that might need more digging into is the fact that I have noticed regular gas does give better economy. Some of the scientific sites agree that premium gasoline will give lower miles per gallon due to the fact that the engine produces better performance.
but if the gx manual says regular is recommended, then surely let's make use of it

 

It may not be a scientific reason that premium gas gets worse mileage in a vehicle designed to run on regular.. If one puts premium in a vehicle that runs on regular for more performance, it will probably be driven accordingly. The difference between the way I drive my truck and the previously owned GS400 is like night and day. I don't miss the 300 HP and am very satisfied with the power of the GX under all driving conditions encountered so far.

 

what i mentioned about mileage earlier is not my personal opinion. i was only re-iterating what i read on several different websites. as a example:
here's an article that explains it. as per the article, in the last paragraph. "In general, the lowest octane in your area delivers the best mileage."

http://www.lubedev.com/smartgas/octane.htm

 

When the regular gas price is above $2.00 , I don't think the extra 20 cents for premium makes that much different...

 

Your kidding me right ?????? You think that someone should buy a car or truck based on the type of fuel one might or might not buy? I think one buys a vehicle for the build quality, and internal features as well as name recognition. But, I don't think someone would prefer to buy a lesser car because they had a Premium Fuel Phobia. Perhaps, I am reading your statement out of context. It just struck me as really bizarre.

 

Lex400 - That article echos the research I found on other sites as well. The second to final line appears to summarize it best... "In general, the lowest octane in your area delivers the best mileage". This article seems accurate in refernece to the GX from my experiences.

 

Today's Wall Street Journal has an article on the differences between gasoline brands and grades. One on hand, it has statements like:

"since all gasoline must meet government minimum standards for certain key additives, in most cases, it doesn't matter what brand or grade of gas gets put in the tank."

"often the suppliers are the same ones providing gasoline to the major gas-station chains."

It gives as an example, "Costco is the same fuel that branded stations such as Shell and Chevron and BP typically sell, often from the same refineries." But it goes on to say it's not exactly the same: "The difference is that the branded fuel contains a small amount of detergent...."

On the other hand, to give credence to those who say that certain brands are better than others, the article recommends for those using cheap gas to use a detergent additive "as infrequently as every 3,000 miles." Or to "fill up occasionally on branded gasoline that contains extra cleansing compounds, and then buy discount gas the rest of the time," which "should be adequate to keep values and fuel injectors from clogging."

It also quotes a AAA spokesman recommend buying regular gas "even for cars in which the owners manual recommends a higher octane gasoline." If the car pings or knocks, then "switch to a higher grade."

 

ET - Interesting artical but it looks more like a basic "which manufactors product is betterl is better than another" rather than a "best fuel for your car" article. I've seen these before and most say that they are all about the same (a good way of using space to say nothing). Some argue that Texaco is better than BP but for the purposes of this thread, I don't think a brand recommendation is what we pursuing here in this thread but rather "Should use regular or premium in the GX". The final line you quoted can do as much harm as good in that a car CAN use lower grade fuel and NOT ping but it may also result in worse fuel economy. Just because the car does not ping when run on regular is NOT a good reason to use regular fuel. Fuel economy being better when running a car on regular is a valid reason. Maybe splitting hairs here?

 

My X-GF has an M3, to see if regular verse premium really was different we ran it to almost empty and filled it with regular, thing was about as fast as a 325 but still it drove, got up to speed and handled, just lost the jet like take off, never pinged or knocked

 

I think brand is relevant to the "regular vs. premium" debate because a big reason a GX driver might choose premium is because of the extra additives premium has (that's the main reason the Lexus service manager at a recent owner's clinic I attended stated when he emphatically recommended premium over regular). So it may be that premium IS better, but only certain brands.

Higher compression engines run better on premium, right? I think Lexus engines have 10.5 to 10.8 compression ratios. That's considered high, right? I just checked the Porsche 911 Turbo's specs, and its compression ratio is 9.8, and Porsche recommends premium.