Fuel

The 3.4 uses 87 octane, unless you have the supercharger(91 or 93) or maybe have some carbon buildup and it pings(maybe 89). Second gen 4.0 ECU will detune to run 87, but it makes the most power and get the best mpg on 91 or 93

 

I had a 2002 tundra 3400 v6 , I ran 91 in it continuously for about 1500 miles . My check engine light came on I hooked up my diagnostic code reader and p0420 bank one came up . So I did intense research on what what the problem was . Come to find out my I burned up my first in line catalytic converter . Well I also found out , by putting in 91 octane my upstream o2 censer was running lean and deposits from the 91 octane were running my first cat hotter because of the lean burning gas which and left residue that wasent burning off from inside the catalytic converter there for burning it up . So in my thought I will not run 91 im my 3400 v6 again . I talked to toyota and they told me that the engine is designed mixture wise to run on 87 only or lower . I would love to run 89 but i dont want to take a chance as my tundra cost me 1500 buck to replace both cats and up stream o2 censer .

 

I have never heard of an engine designed for 87 to harm it with anything higher. All octane is is resistance to detonation, and if the compression ratio is still the same, it's not going to do anything but cost more

 

I have a 2002 as well with over 170K miles that has seen nothing but 91+ in it with zero issues. Stock cats are still on her too. Maybe you just ran into a batch of bad gas. I run Costco Super and will continue to do so.

 

Chevron 87 with 2-3oz of 2 cycle TCW3.

 

In what country you use 85? In CA. the lowest is 87.
thanks

 

Well maybe your right , I would love to run 91 in my tacoma but my Tundra with the same engine was a nightmare dealing with the cats .

 

At higher elevations you don't need as high an octane. So you can find 85 in the mountains