Did an interesting bit of analysis...

"Smallbear wants a modern Syclone, local Maple Leafs spammer" (smallbear94) 09/18/2015 at 08:41 • Filed to: None

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Yes, yes, I know that it's just the octane rating, which is just the anti-knock properties, but...

Going over a period of my driving (this winter) when my driving on every tank was nearly identical (all commute or equivalent balance), I tried a bit of mid-grade gas.

My average on mid-grade was 6% better than on regular. One tank was actually 10% better.

Mid-grade costs about 6% more.

So, why buy regular? Even if a vehicle doesn’t need more than regular, it will definitely not run worse on mid-grade. If, therefore, I get a little more range out of mid-grade, and it costs the same, it’s just not worth putting regular in. In any case I've just filled up with 89. If this has a similar result, good enough as far as I'm concerned.

supra-squirrel > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/18/2015 at 08:49

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Please keep us informed on what you find. I am very interested in a real would test to validate some of what I already suspect.

Party-vi > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/18/2015 at 08:55

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If you try premium you may find that your increase in efficiency also off-sets the increase in cost of the premium fuel. Your engine can advance timing as much as the ECU will allow with higher grade fuel, meaning you’re getting as much potential for efficiency and power out of that 5.3L that you can.

ETA: There was always a noticeable difference in economy in my Renix Cherokee with premium, so I always ran premium.

Firewrx234 > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/18/2015 at 08:56

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Many cars are tuned for different octanes. I’ve seen some cars that even recommend regular 87 octane. They can take higher octane but get no better fuel economy than what they do on 87 octane.

My Charger is built to run on any octane but tuned to operate better on mid grade. This means that I’ll lose a few mpgs using regular but it won’t be detrimental to its health. (I still use mid grade anyway). Whereas, my C250 requires 91+ octane because of the increased compression. So running on regular or mid grade could be bad for the car, especially for prolonged amounts of time.

Smallbear wants a modern Syclone, local Maple Leafs spammer > supra-squirrel 09/18/2015 at 08:58

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Sure. I actually did it just because I like to get some of the detergents once in a while, but I was just going through it and found it was actually significantly better.

Which is wierd, since octane rating isn't actually related to power or economy. I did hear from one tuner that when he did a truck like mine that there was a lot of spark retard and pinging, so it could be vehicle specific, ie mine "can" be run on 87 without blowing up due to its tuning, but has the compression to benefit from higher grade... I don't know.

Smallbear wants a modern Syclone, local Maple Leafs spammer > Party-vi 09/18/2015 at 09:03

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Found this. It’s a bit on a tuners site about a truck basically the same as mine. He does note a lot of knock retard... you're probably right. If I get the same results, from this run of 89, 91 is the next experiment.

https://innovativetuning.wordpress.com/customer-rides…

Smallbear wants a modern Syclone, local Maple Leafs spammer > Firewrx234 09/18/2015 at 09:05

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See my comment to Party-vi. The more I think about it, the more I’m sure that’s what’s happening.

Talk about welcome surprises though :)

Party-vi > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/18/2015 at 09:15

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That’s why GM says you can run regular in a V8 - they’ve built protection into the engine programming.

supra-squirrel > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/18/2015 at 09:16

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Well, my supra needs the high octane and ethanol free to run well, though since I now also own a pathfinder I have accidentally put high octane in and it seems to run significantly better than the midgrade, tank also lasted a lot longer in a highway drive than it did previously. Trip to Atlanta took a quarter tank instead of almost a third round trip.

WhiskeyGolf > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/18/2015 at 09:59

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I’m going to try this next time I go for an extended spirited drive through the forest. I should also point your findings to my dad, who puts regular in his 328i because it “doesn’t seem to harm it.” Maybe not, but think of those horses that have run away!

BigBlock440 > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/18/2015 at 10:19

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I think it could be that it has less ethanol in it, at least that’s the theory I’ve heard. Ethanol has such a high octane rating that really crappy gas (40 or 50 octane) can be mixed with it to achieve the required 87. With the upper grades, you start with better gas and need less ethanol to bring it up to the required rating.

Smallbear wants a modern Syclone, local Maple Leafs spammer > BigBlock440 09/18/2015 at 10:27

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Could be, but I doubt it. In Ontario they can all have up to 10% Ethanol, but no more (unless they tell you and sell it separately).

BigBlock440 > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/18/2015 at 10:38

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That’s the same as here, and the “up to” is the key. Still, even if they use the same amount of ethanol, the upper grades start with a higher quality base with more potential energy. I guess it still comes down to if your vehicle can actually use the higher potential energy or not.

Smallbear wants a modern Syclone, local Maple Leafs spammer > BigBlock440 09/18/2015 at 10:44

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OK, then that could be the case. Though I would think that the higher grades would actually have more ethantol, as an easy way of raising octane. Who knows what the oil companies cook up...

I’m actually wondering if it can use it. See my reply to party-vi. Seems promising. If so... welcome surprise :)

Snuze: Needs another Swede > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/18/2015 at 12:34

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The General says the Snuze is rated for 87 octane, and it will run on it... like a dead dog. It pulls so much timing out and retards boost to keep the engine safe. I switched to 93 octane and saw a significant difference in performance and fuel economy. As many have said, a lot of the newer engines will adjust their timing based on the fuel you’re using to keep the engine safe. So a lot of engines *can* run on 87, but that doesn’t mean they will run best on it. And as you have seen for yourself, the gains in economy and performance often offset the cost.

Now with the tune I am required to run 91+ because of the added boost and timing.

Smallbear wants a modern Syclone, local Maple Leafs spammer > Snuze: Needs another Swede 09/18/2015 at 12:40

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That’s one thing that comes into it for me, actually. I was thinking of getting it tuned, and while they can tune to get the most out of 87, I’ll probably see enough gains on 89 or better to just base the tune off that. Of course provided that it will run on 87 in a pinch.

Maybe I could just carry around a bottle of octane booster...

BobintheMtns > BigBlock440 02/16/2016 at 12:40

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Higher grades of gasoline have more ethanol in them. And all gas is the same ‘crappy gas” to start with- the differences between low and high grade is the amount/quality of additives to bring it up to spec. Regular gas has the absolute minimum of additives to get it into spec, Premium has all the good stuff added- and mid-grade is just a mixture of the two.

I did a bunch of fuel testing back in the day- and we did a lot of experimenting on ethanol blends and ratios into gasoline- and on paper, because ethanol has less btu’s than gasoline- the more ethanol you add to the fuel, the lower your fuel economy should be. However in lab testing, we found the opposite: ethanol actually raised the fuel economy. It wasn’t until about a 25% blend that we saw fuel economy drop to where you’d mathematically expect it to be...

We surmised that while gasoline has more btu’s, not all of it combusted. And by adding ethanol, you’d increase the combustion efficiency- creating higher fuel efficiency while using a lower btu mixture.....

Edited to add- in the testing I referenced, we were using motorbikes that didn’t have computer controlled FI/spark advance, etc.