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post #21 of 32 (permalink) Old 05-15-2014, 08:00 PM
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Went through with the dealer on this one..
87 for ls
91 for SS
Said you'd be doing harm then good... For one said your Cadillac convert wouldn't last as long cause of the extra additives that aren't being burnt..

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post #22 of 32 (permalink) Old 05-15-2014, 10:00 PM Thread Starter
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And what are these additives if I may ask?

Shell is touting their nitrogen enriched gasoline. It sounds like BS to me. 78% of the air we breathe is nitrogen. Supplementing more of it doesn't sound like it would do any good.

But I'm no chemist. Ask Swanman lol

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post #23 of 32 (permalink) Old 05-15-2014, 11:03 PM
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Well here's the thing on that.. nitrogen in gas acts as a detergent. Just like the detergent all gas has in it to clean carbon build up. It's supposed to clean the carbon build up out of the engine, which then makes the engine more efficient, because a "dirty" engine wont perform as efficiently as a clean engine. Sure, it sounds like a good idea and all, but like i said before.. all gasoline now has detergents in it to clean carbon from an engine.. does the nitrogen clean it better? Maybe.. Shell's "nitrogen- enriched gas" does exceed the EPA's requirements for gasoline.. but in my opinion it isn't going to have a huge impact on our engines.. it will increase nitrogen oxide (NOx) levels, which is a huge contributor to pollution(acid rain, smog, etc). I don't think running 91 in an ls will harm it at all though.. the "additives" are just detergents to help clean the engine a little more and to burn the fuel more efficiently.. i dont see how that could cause harm to anything.

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---------- Post added at 10:03 PM ---------- Previous post was at 09:55 PM ----------

Also the octane rating wont give you much better gas mileage or any kind of performance increase in a low compression engine. The higher octane gas is less likely or more resistant to spontaneous combustion. You may notice a small increase in gas mileage, but in reality you're not saving money because of the extra money soent on the gas. Now in a high compression engine you want to run high octane gas to prevent detonation

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post #24 of 32 (permalink) Old 05-16-2014, 12:48 AM
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No ethanol in my area. Best brew on tap is 94, and only at certain stations.

Doesn't Colorado usually have higher grade gas than other parts? Something to do with high altitude and less oxygen molecules in a given amount of air I think.
Because of the altitude in Colorado we can run cars on a lower octane rating versus being at sea level but like in a couple days when I go to AZ Im gonna fill up on 87 since thats premium here in colorado but Ill being decreasing in altitude
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post #25 of 32 (permalink) Old 05-16-2014, 06:00 AM
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Because of the altitude in Colorado we can run cars on a lower octane rating versus being at sea level but like in a couple days when I go to AZ Im gonna fill up on 87 since thats premium here in colorado but Ill being decreasing in altitude
Altitude has no effect on gasoline, your fuel injectors adapt to different environments and altitudes. When TBI and MPI was popular, yes, it did make a difference and a sensor was required for different altitudes. Not today though and carb'd engines you would have to adjust your jets for different altitudes.

Octane ratings are based upon combustion of the fuel atomization. It does burn a bit cleaner, but not a real HP gainer. Different engines require different octanes to keep the engine from detonation. The nitrogen enriched fuels act as what someone said correctly, a detergent, to clean up your intake valves and the top of your pistons. Its more of a carbon cleaner

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post #26 of 32 (permalink) Old 05-16-2014, 10:34 AM
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From the owners manual...

Gasoline Octane
If the vehicle has the 2.2L L4 engine (VIN Code H), use regular unleaded gasoline with a posted octane rating of 87 or higher. If the octane rating is less than 87, you might notice an audible knocking noise when you drive, commonly referred to as spark knock. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible. If you are using gasoline rated at 87 octane or higher and you hear heavy knocking, the engine needs service.

If the vehicle has the 2.0L L4 engine (VIN Code X), use premium unleaded gasoline with a posted octane rating of 91 or higher. You can also use regular unleaded gasoline rated at 87 octane or higher, but the vehicle's acceleration could be slightly reduced, and you might notice a slight audible knocking noise, commonly referred to as spark knock. If the octane is less than 87, you might notice a heavy knocking noise when you drive. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible. Otherwise, you could damage the engine. If you are using gasoline rated at 87 octane or higher and you hear heavy knocking, the engine needs service.
Where's the verbiage for the 2.4??
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post #27 of 32 (permalink) Old 05-16-2014, 12:29 PM
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Looked it up, 2.4 is the same. If you don't live in a mountainous region and you don't pull a utility trailer you don't need super or premium.

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post #28 of 32 (permalink) Old 05-23-2014, 08:48 AM
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It has to do with direct injection, a car cannot detonate if fuel isn't there yet. Plus now with both variable cams you can play with ignition timing a lot more so you don't need gas with reduced volatility.

Look at the new Buick Encore, it is Turbo and still runs on regular gas recommended by GM.
Ah I see.

Re. the cams though, a knock sensor would retard the timing until it won't knock but that doesn't mean we're getting the best out of the car as we could. That was my logic behind better mileage. Adding higher grade gas would let the knock sensor increase timing ahead of regular. That's just my theory. I am not an engine designer though

Also, a turbo by itself need not require higher grade right? It would depend on what the pressure the turbo is letting through is. A turbo with a richer mixture would decrease chance of knock on an engine running regular. Plus, it is a really small engine. A 1.4 could do away with a lower compression ratio and a turbo and give higher power (like an SUV would need) but low gas mileage. If the gas mileage is better than most other comparable SUVs though, a customer wouldn't complain. The CR on that is 9.5:1. Again, I don't really know. I am just reading stuff online and educating myself. I don't know an engine designer, unfortunately, to ask the technicalities.
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post #29 of 32 (permalink) Old 10-23-2014, 01:58 PM
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Higher Compression = Higher required octane level to avoid pre-detonatoion or "knocking"

What does octane mean? - HowStuffWorks
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post #30 of 32 (permalink) Old 10-24-2014, 03:32 PM Thread Starter
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Have you seen Mazda's SkyActiv stuff? Super high CR, regular gas. Not sure how it works.

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