coolsaber

I know its hard to understand, but as they say. Do what makes your feel happy, as long as its not ur engine not ur concerns lol (no disrespect meant)

Toys4RJill

Simply trying to help out. Premium fuel vs regular fuel is a very real thing. Toyota historically tested and rated all of their engine options with premium fuel. SAE rules changed things. Its poor advice to go against what the manufacturer is recommending.

As for engine knocking. It is possible to have engine knock and not be able to hear it. It is more serious when it is audible but using the human ear as a guide is wrong. The fact that the GX has a slightly more restricted exhaust, is always turning the center differential, has a very good 1400lb payload capacity and has a 6500 lb capacity tells me that GX460 will perform better with the required premium fuel set by the manufacturer when used for what is can do.

jjscsix

i don't dispute what you think about the 3.5 as I have not studied it. I also explained that some vehicles control knock with sensors and they absolutely may perform better on premium.

The SINGLE issue for me is whether or not the Toyota version and Lexus version truly are identical engines and whether or not Toyota truly does recommend regular and Lexus recommend premium. That is 100% the basis for my decision. I believe that the answer to both is yes.

Toys4RJill

The set up to the 4.6 in Toyota trucks and that of the GX are not exactly the same. The exahaust system is more restrictive in the GX, there is the always turning Torsen differential, a cooled exhaust gas recirculation system. So to get the peak rating, you need premium. The timing is going to be different as well compared to the Tundra. Lastly, knock sensors do wear out.

Acrad

Looks like the 4.6L in Tundra has that as well.

http://www.fourwheeler.com/vehicle-r...engine-review/

"The new 4.6 V-8 also uses water-cooled exhaust gas recirculation (EGR), which lowers peak temperatures inside the combustion chamber. In the new 4.6, a computer controls the timing and amount of cooling the exhaust gas receives before it is recycled through the combustion chamber, so the combustion process is never over-cooled. Generally speaking, cooled EGR provides an emissions benefit, but it's also known that the technique improves overall efficiency, which translates into better mileage."

S2k4

Regardless of Premium vs RUG, I have noticed the blends in pumps now (August/September) show me significant less range after a fill up.

jjscsix

How do you know the timing is different? Does it actually have knock sensors? Those are the only two things that would concern me. It's not like Toyota has a different octane rating when in AWD or towing a trailer, and the exhaust is very unlikely to make a difference.

lobuxracer

iTrader: (2)

Yes, fuel grade affects economy. My Supra with its 8.5:1 compression didn't like 92 octane when Tosco decided no one in California needed 93 octane anymore. I put in 80% distilled water and 20% coolant to counter the sudden drop in AROUND TOWN fuel economy and it worked. Then, in their infinite wisdom, they decided to reduce premium to 91 octane, I went from 18 mpg around town to 12 mpg around town. NOTE: this is not WOT, not heavy load, just driving stop light to stop light. I ended up putting 4 gallons of 100 octane unleaded with 12 gallons of 91 premium (at $7 per gallon for the 100 octane) to get my 18 mpg around town back.

I put the numbers in a spreadsheet for analysis. It was cheaper to run the 4 gallons of race gas with the 91 premium than it was to just suffer the MPG loss of running 91 octane.

Most importantly, this is in an engine with 8.5:1 standard static compression, not running boost, just driving around town. It pinged mercilessly. I did everything possible to decarbon the engine, and to ensure the cooling system was working at peak efficiency, and this is a MANUAL, not an automatic adding heat to the cooling system from the transmission.

A 35% efficiency loss from running only 2 points low is pretty sad. It makes be believe CA 91 is really 49 state 89 in disguise. Regardless, I have the data to prove it, and I am not kidding when I say I moved to Georgia to get my mileage back 10 years ago.

GB2011GX

Glad to hear to exited the GRANOLA State Lobuxracer! LOL (jk) Welcome.

Craigyyy

Marketing.

So you feel like you bought something more special and refined than a Toyota Tundra.

Htony

If saving some $$ is priority one, then one should drive any vehicle designed to to run on regular Octane.
If manufacturers suggest to use high Octane fuel then so be it to make the vehicle run at 's full performance
level.
I just wonder drivers who claim they don't feel difference between two different grade fuel. As a retired
engineer(EE class of '60), I trust what fellow enginners(SAE) say. Only car running on regular gas is wife's
Subaru. No, I wouldn't use regular gas on two Bimmers or My RX hybrid. I alwaysy fill Shell premium. If I
switch to Esso, or Petro Canada I feel difference even at same Octane rating. Even exhaust gas smell
different.

jjscsix

i trust what engineers say also, but we don't know who had the say. Certainly the engineers have enough clout to dictate what mininmum octane to use. But if there is no negative effect of running a higher octane than the engine really needs do you think there is some chance that maybe marketing could make that call?

Htony

Marketing has quite a bit of influence. The reason Chrysler went bankrupt. The company I worked for many years went down tube because marketing insisted on what to do with future product development. That was migrating from old closed OS to open source Linux(Unix) against engineers suggestions for short term gain. The GM PU truck fuel tank incident. To save 10.00, they mounted the tank outside frame which cause fire/explosion when truck got involved in an accident. Any one who works on short term gain loses at the end always.

Regarding Lexus design, engineers' version of such a bold design(specially front end) was quite milder compared to what they are now. Guess who made the change?
I wish some day, an engineer will be a president/prime minister of a nation.....

Acrad

A little off topic...was it something like AIX or Irix?

Htony

Ancient story. GCOS, CP5, CP6, Multics, etc.