2006 GS 300 RWD. What's more important, high octane or no ethanol? I live in an area that doesn't have both, so I have to choose. -Thanks

 

That probably depends on the ethanol concentration, but it's not unlikely that high octane fuel with 5-10% ethanol is the better choice. What is the ethanol concentration in the gas?

 

So I understand.. Your area has neither Ethanol or higher octane? What exactly is available then in your area?

 

I can either get 87 octane no-ethanol gas, or 'up to 10%' ethanol 93 octane.

The up to 10% is available in all three octane grades, 87, ??, and 93.

 

I personally would choose the ethanol-free 87, then use an octane booster to get it up around 91-93. It's not NEEDED, but couldn't hurt

 

I would steer clear of 87.. The specs are 91+.. 87 Octane may cause detonation or "pinging" and that can be a bad thing.. 93 with 10% ethanol would be acceptable and is considered a safe blend for these cars. These engines are 11.5:1 compression with high timings, so 91+ is where you should be.

 

Definitely choose octane over ethanol.

 

With lower octane your ecu will detune performance by changing timing to prevent engine damage thru the knock sensors. Ethanol will leave behind corrosion and is one of the main reasons for the recalls with fuel leaks like the recent high pressure sensor gasket and having to replace fuel rails due to the ethanol eating up the inside lining in early 2006 gs300. You can also add ethanol fuel treatment thats popping up everywhere now in auto stores. I do recommend sticking with correct octane especially in the hotter weather. I do believe all 3 grades now have some ethanol in it anyways

 

SilentM, Do these problems this apply to GS350s??

 

No the gs350 already have updated part. The fuel pressure sensor gasket they are replacing right now

 

As others said, octane is more important than ethanol content, however if you are going to leave gas in the tank for months then re-consider.

Low octane is bad if you are driving, ethanol is bad if you are not.

Ethanol in the gas does not corrode gasket/fuel line by virtue of being there, what it does is cause is slow increase in water concentration over time which in turn causes corrosion. So if you fill up and quickly burn through it gasoline with ethanol should be no problem. However if you let it sit in the tank for a couple weeks in a humid climate then yes it can be a problem. let it sit for two month and the car will straight up start misfiring. Thats why they suggest premium gas in lawnmowers, its not for the octane rating as 91 octane is a waste on engines with compression ratios like 8.5:1 for the Honda GCV190 for example. The problem is that you leave the lawnmower in the shed for 2 or 3 weeks with a bit of ethanol in the tank and you basically kill it.

In my view, premium gas with ethanol is simply unacceptable. Only PetroCanada does that here and so i avoid it like the plague