Gasoline Choices
 

Where I live in the summer, (out in the sticks in Central Oregon) unleaded 91 is my only choice. I also can easily get 100 octane leaded avgas.

For a Vortec supercharged engine would adding a octane boosted work or should I use a 91 unleaded and 100 avgas blend? And is so, what ratio?

DO NOT put leaded gas into theses cars
91 will do just fine .

Someone will chime in on the reasons

Burn the Cat's out, I didn't think of that.

I'm not wanting an all out race car, just a fun daily driver I can take to the track. So with a good Dyno tune 91 is OK with the Vortec?

Wouldn't the lead potentially foul up the plugs?

You have easier access to 100oct than e85?

Just run 91 like the 40 million people in California do.

Will do, makes life easy for me. With all the talk about E-85 I just wasn't sure if 91 would be OK.

I had no choice but to fill up at a 7-11 the other day, I chose 91 of course but after the fill up, I noticed the car seemed to be lacking, I have my speculation, I think the 7-11 charged me for 91 octane but ended up giving me 87 or 89. At any rate, it prompted me to try doing a blend with 100 octane, just to make sure I was getting at least 91, but I was shooting for a 93 octane blend. just so happens there is a VP gas station a block away from my house that has 100 octane VP street blaze it is unleaded. I talked to the guy working there to get his thoughts on the blend ratio. he told me if you run 91 and you go with a 50/50 mix of 91 and 100 octane, the result is 95 octane, so he told me to run a 70/30 mix to acheive 93octane. needless to say I noticed a tremendous difference in power right after adding the 100octane. I wouldn't make it a normal thing to do just because the price ($8.89/gallon for 100octane)

More likely a placebo effect in reverse!

Kay I honestly don't understand most people in the US are using 91 octane fuel unleaded. I own a toyota 86 FT in argentina, and the owners manual says.

Fuel type : unleaded
Octane number: 98 or higher

If 98 NOI it's not avaialbe in you region, you may use a 95 octane NOI without affecting durability of the car.

How come ? I don't get it what do your owners manual say. Cause the engine it's the same on my car and on SCION FRS

yes, I think it was all in my head, Its the first time I have not fueled at either a Shell or a Chevron, and I have my reservations. I always hear from others there is no difference in gasolines, all gas comes from the same place etc etc. I still have my conspiracy theories though lol

Gasoline Choices
 

Our manual says to use 93 octane. If that is not available, 91 octane can be used as a substitute.

We most likely have a different octane rating system than yours. I know US 90-94 octane rating is equivalent to European 95-99 octane. It may the same in South America as well.


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So you're saying that the octane rating here it's lower than in the US ? like 91 from the US would be equivalent to 98 ?

They're right!

There's a tank farm near QCOM stadium where various brands fill up with generic gasoline. The driver then plops a brick of aptly named "additives" in the tank and shoves off for his first delivery. How the brick is supposed to dissolve and mix in uniformly with a tank full of fuel in time for the first station down the road is anybody's guess.

I've never had any problems with Costco fuel. Somehow I trust them more than the fru-fru brands. They certainly have the freshest fuel since half the time I see a tanker unloading. I can't remember the last time I saw a tanker at a Chevron station as I drove by...

Octane is measured differently in some countries. The mon/ron ratio is different.

Someone who isn't lazy may want to explain .... :cry:

Something along those lines.

Here's a simple explanation from wikipedia:

In most countries, including Australia and all of those in Europe, the "headline" octane rating shown on the pump is the RON, but in Canada, the United States, Brazil, and some other countries, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI, and often written on pumps as (R+M)/2). It may also sometimes be called the Pump Octane Number (PON)


To get back on topic. I'm sure it'll be fine sticking to 91 even after going FI.

I think it's 93 (R+M)/2 (US) = 98 RON (Euro), if I remember right, but I could be wrong...

Ok so now I think I got it in my country it's stated as RON+MON/2 and in the US it's not that nomenclature right? so US 91 would equal a 95 octane in my coutnry?

Not sure how true this is, but a buddy of mine drives truck, and said that the Techron they use at Chevron is just one bottle that they dump into the tank of a whole truck full. Maybe it's super concentrated? I know it's off topic, i've just always wondered.

Can u use e85 ...


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I only use Shell V-Power 93 here in TN. If only they didn't use any ethanol, it would be perfect. If all you've got is 91 though, go with that. That's the very minimum you want to use in this boxer engine.

Mine (and all my four-cylinder cars) run best on unbranded 93 octane Stop & Shop grocery store gas. Their additive pack seems to be well suited for smaller high performance engines. I started out using Shell V-Power but the FR-S and the MX-5 both run much better on the grocery store gas.


My V-8 Mustang runs terrible on the grocery store gas and I have to use Shell V-Power 93 for that. BP Ultimate 93 works well in the Mustang also but it's hard to find in my area.

Basically, there is more than one way to actually measure the octane of a fuel (as in, laboratory methods). The two methods commonly used with automotive fuel are RON and MON. Most of the world only lists RON as it gives them a bigger number. MON mixes up the RON test a bit to better simulate how an engine actually behaves. (Just consider their first letters: RON=Research, MON=Motor) The United States (and presumably, those countries dependent on US refining capability) average the two together, giving our comparatively lower rating.

Aviation fuels use yet more mechanisms to measure the octane, so 100 Low Lead (current standard for AVgas) cannot be directly extrapolated to 100 octane as it would be rated on automotive fuels. Aircraft engines operate at significantly higher altitudes than automotive engines and are run at 80% power continuously during cruise. As you'd expect, that requires different testing conditions for the rating system.

Also, the lead content is AVgas is super high. Despite being called "Low Lead" (or even "Very Low Lead"), it's lead content is significantly higher than automotive fuels ever were. And the danger from lead poisoning (of the engine) is far from theoretical. It attacks the cat, O2 sensors, and the sparkplug gap (especially at lower power outputs). You'd probably end up with a CEL before finishing the first tank. Oh, and the fuel is dyed blue, so it would be pretty trivial for anyone to see you were doing something wrong.