Also, you should only get "Top Tier" gas for your car, which has extra cleaning agents. I always look for this when I fill up and there's clear evidence that it helps keep your engine cleaner. Costco has it and so does Shell and quite a few others.

https://www.consumerreports.org/car-...h-extra-price/

https://en.wikipedia.org/wiki/Top_Ti...rgent_Gasoline

 

The Top Tier standards must apply to all grades of gasoline that a company sells, whether it is economy (low-octane) or premium (high-octane).[2]

 

Google Car Talk then read these:Premium gas gives you more miles per gallon than regular gas.
Premium has special or extra detergents in it that are worth the added cost.
I will void my warranty if my owner's manual calls for premium and I use regular unleaded.
Using regular gas in a car designed for premium will definitely damage the engine.

 

It does not matter what that website says because it has no credibility. That means that the info it provides are highly susceptible to being inaccurate.

If Toyota says to use premium fuel only, then wouldn't it be wise to listen to them since they made the dang cars? Also, it doesn't matter if one gets better mileage or no knocking as these things may or may not be associated with the different grades of fuel. No one here is an engineer.

 

Interesting theory.

 

I just changed oil and experienced 1-2 mile improved mpg on 89 octane gas. Did not notice mpg or performance difference going from 91 to 89 octane.

 

Yours must be special, because mine says nothing about octane. And like I mentioned earlier, the manual specifically says "87 or higher."



Since my last comment on this thread, I've used 87 octane without ethanol on two tanks, and my average mileage is still higher than before. The higher octane gas I was using before also has no blended ethanol, so apparently it's the ethanol that pulls my mileage down.

 

I guess I must be special since all my vehicles(gs,rx400h) state in large letters "premium fuel only" inside the gas caps. But it's pretty interesting that the manual says 87 or higher. Idk, I still think it's much better to follow what the manual says in general rather than relying our shadetree mechanic skills.

 

So far I've had no issues using 87 octane in our 2007. The compression ratio is lower in the hybrid motor compared to the non-hybrid Toyota V6s. I see no difference in fuel economy and the sister Toyota Highlander Hybrid does not say "premium fuel only." The skeptic in me thinks Toyota/Lexus did this for a prestige factor in the brand. 180K miles and no complaints so far.

 

never a problem

Shell regular though

 

To add to the confusion, my 08 RX400h recommends 91 Octane. i just had an engine swap with a 07 HiHy and the manual just say 87. I have used mainly Costco premium (top teir) for mine and was surprise to see the build up in the piston and valves. Granted I did not know what the previous owner used.

From 400h manual.
"Fuel selection: Select Octane Rating 87 (Research Octane Number 91) or higher. For improved vehicle performance, the use of premium unleaded gasoline with an Octane Rating 91 (Research Octane Number 96) or higher is recommended."

The engine is a 3MZFE with a 10.8:1 compression ratio. (it is listed by Toyota that it is a reduced output for rx400h and HiHy) I am not sure what the difference is in the newer hybrids the change is that they actually change the compression ratio and turn it into a Atkinson cycle engine-the RX450)

Also interesting read about this engine on 87/91 when it is used on non-hybrids https://www.v6performance.net/forums...um-3mz-fe.html

 

Those are not Atkinson cycle engines.
Cycle is simulated by VVT-I. Atkinson engine has components not present in hybrid engine. It's fake, just as calling PSD a CVT.

 

I recent took my car to a new mechanic, a nice old Japanese man who specializes in Toyota & Lexus, to get the a/c checked out. He says I should always get 91-octane name-brand gas and inflate my tires to 40 psi. (5 psi above forum members recommendation). I followed his advice two weeks ago and went from 18 to 24mpg in city stop-and-go traffic (80% of my driving) and 30 on open freeway. Just FYI.

 

I had 450h once. I just follow owner's manual, premium Octane 91 or higher and premium quality engine oil.
If you use regular will lose couple horses and up and go. If you're planning towing something chance for pinging
which is bad for the engine.

 

Specially if one intends to drive the car for MANY years.... I don't understand folks who buy cars like Lexus trying to pinch cents and dimes on fuel. I never read read topic like this on BMW, Audi forums where I used to go. I am an engineer retired but EE.