The last gas question

[keesue]

Yeah, its fun. Kinda like the efficacy of 0-20 v. 5-20 and whether its recommended or not. Heh...

[1stToyota]

Originally Posted by Ace

Someone please show me where Toyota indicates that the U.S. Yaris or the NZ series engines were designed for 87-octane gas. Or that it runs better on 87-octane gas.

The Smart requires premium gas; Yaris has a higher compression engine.

Simple. Factory tuning. Ever heard of canned tuners like Diablo, SuperChip...? Even they can be tuned for what octane you want to use. The Smart is tuned for premium and performance will fall off if lower octane is used, sort of like my GTO...I could get by on less than 91, but car was tuned for 91. Unlike the Smart, the Yaris isn't tuned for 91

And on page 384 ('08 manual) it says **87 octane or higher**
so I might try mid-grade for a while and see

[360cubes]

Just to note here that I operated and managed two service stations for six years. Companies advertise "may contain up to 10% ethanol" on the pumps to make you, the consumer feel better that you're somewhat helping the environment. However, go back a few years and millions of vehicles on the road can only run up to 5% ethanol content, safely.

Most loads of fuel that were delivered never contained more than 6% ethanol - ever. The most ethanol content was found during the winter months, to increase the freezing properties of the fuel (hence, "winter gas"). In the summer, ethanol content was around 4-5% average per load delivered. In reality, we have 'winter gas' all year round! It amazes me how people run out and buy gas line antifreeze bottles for $1/ea when even 2% ethanol content in the fuel means you'll still be able to start the vehicle in -40C weather without trouble. 5-6% means it'd have to be below 55C before you'd even think about having to add anything special to the tank.

E-85 is 85% ethanol, 15% petrol (gasoline) mix. This fuel is meant for E85 compatible engines only. It'll stall and gum up engines that aren't meant for this fuel.

As for the "87 octane or higher" label, this is meant to cover Toyota's rear end should you live in the mountains, for example. A difference in elevation (even as much as 2500ft above sea level) can lead to engine ping due to lack of oxygen, which will require you to run a higher octane. The engine will automatically compensate for the octane difference (hence, knock sensors). Knock sensors can only control the engine so much. If you drove 10,000ft up a long hill at a steady speed, chances are you'll notice engine pinging around 5,000ft if you had a tank of 87 octane.

Running a higher octane fuel on a regular basis won't harm the engine. On some low grounded areas you can find octane as low as 85 at the pump! Keep in mind the high-ish compression ratio of these cars at 10.5:1). Turbocharged or supercharged cars need not worry about elevation changes, due to the lower compression engines (8.5:1) and the need to run 91 octane fuel irregardless. You can run 87 octane fuel in a modern turbocharged vehicle, but performance will go down the tubes as the PCM is designed for it to operate most efficiently on 91 octane.

As mentioned, a tuner can be used to change the PCM mapping a bit if you wanted to run 91 octane on a regular basis...you might even gain 1hp out of the deal. If you were going to do a few engine modifications, a custom tune would be the way to go to better squeeze out every HP possible from your particular setup. Otherwise, just to tune an engine on 91 octane isn't worth while. Stick with what the factory said unless you live on a mountain top.

My '00 Durango R/T came from the factory to run on 91 octane. However, it doesn't have knock sensors and I cannot run a lower octane without severe ping even at part throttle. I've added performance mods to it anyway that require 91 octane, but if I had left it stock I'm sure I would've found a way for it to run on 87 like 01+ Durango models.