Question 05 Tacoma: Which gas in Denver

mountainboy1904 · #1 (**permalink**) 12-19-2008, 12:29 AM

I just moved to Denver and have already put my 4X4 to good use. They sell 85 octane unleaded and I was curious of it's impact on 4.0L engine? I appreciate your responses.

Forester · #2 (**permalink**) 12-24-2008, 07:45 PM

In general, lower octane gas is all that is sold in high elevation areas because higher octane is not needed to prevent knocking. Just be careful if you drive to a lower elevation area--you might want to fill with higher octane gas before leave the high elevations.

acidchylde · #3 (**permalink**) 12-30-2008, 01:18 AM

Technically, you need to use at least 87 or the mid-grade around here. The manual specifies a minimum research octane of 91, which is slightly different than the number on the pump. Search and I think you can find a full explanation if you're interested.

Personally, I ran 87 for a year when I first got mine, and then switched to 91 for a year. The difference was very very slight. On 16 tanks of 87 over one year my average was 20.1. On 32 tanks of 91 over one year my average was 20.3. If I look at the actual per tank numbers, all of the lowest numbers (anything below 18.2) were on the 87, but so was the highest at 24.9.

(BTW, I have an Auto V6 4x4 TRD Sport.)

furiousgwedo69 · #4 (**permalink**) 01-05-2009, 06:45 PM

wait wait, whats the recommended fuel? is it midgrade? what happens with regular unleaded? bad stuff?

acidchylde · #5 (**permalink**) 01-07-2009, 07:33 PM

The recommended fuel in my truck manual is 91 research octane, which in the US is not the number that appears on the pump. The number on the pump is an average of research and 'motor' octane. See these two links:
Octane Explained
Octane rating - Wikipedia, the free encyclopedia
Whether that's regular, mid-grade, or premium, or some other 'grade' depends entirely where you are in the country.

As for what happens if you run lower than recommended? That's debatable. You're theoretically robbed of power and efficiency (mileage), though running a higher octane doesn't generally improve either. Also, the truck has a computer controlled engine and will make timing adjustments to compensate if you're running lower, so you may or may not hear knocking. If you do, that means it's too low to compensate for. And if you switch fuels, expect it to take at least a couple of tanks to adjust itself. You can speed that up by disconnecting the battery (resetting everything).