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I found this article on Jalopnik today about Premium Vs Regular fuel in a car that recommends Premium.

http://jalopnik.com/why-putting-regular-gas-into-a-car-that-needs-premium-w-1796463139

The article is somewhat informative and gives you a few things to think about. Personally, I use Premium only, but thats just me. As they say... Your mileage may vary...
I for one, think some cars can run on regular, instead of 91 oct. beside the high performance cars. I have used the 89 octane and noticed no difference between 91 and 89, in performance or economy. But due to EDL, I still had 89 octane in tank, but was suggested to switch to 91. I understand the EDL makes the engine more performant and therefore run 91 octane makes more sense.
 

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Run exclusively 93MON(98RON). It's a turbo. It'll put it to good use. For sure the car will be dialling back the output to preserve itself if you run less than 91MON in it.
 

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It has to knock to know it needs to pull timing. I'd rather it not knock at all.
 

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I mean, typically putting in whatever grade that the manufacturer specifies for it is essentially the route to go. I don't understand why anyone would want to put the lower grade fuel when the engine specifically calls for the higher grade juice. Saving a few bucks here and there will ultimately end up costing you a lot of bucks later on.
 

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Abarth Europe specifies ROZ95 (Super) in the manual of some models and writes: Full power only with ROZ98 otherwise 5hp and 30Nm less.
 

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It should be noted that those running tunes or piggyback boxes should only ever run premium fuel. The same probably could be said for any performance related mods.
 

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There are many factors that go into what octane a vehicle should or can use.

One thing is for certain, however, that turbocharged engines should use premium fuel. I've driven some turbocharged cars that called for 87 octane and while the engine can be tuned to run the lower octane fuel, the result is reduced power and sometimes a rougher running engine, especially in high temperatures and during stop and go traffic where the engine gets heat soaked. The engine just pulls a ton of timing. Modern ECUs are very good at detecting and even preventing knock and responding to it very quickly, but as noted above, I'd rather it not knock in the first place. In addition, not pulling timing due to low octane fuel will also improve efficiency, which negates some of the cost of running the higher octane fuel.

In the 124 Spider, I couldn't fathom running anything lower than 91 octane (US). Fortunately, we have 93 octane where I live, which is what I fill with. The dynamic compression produced in turbocharged engines requires that high octane fuel be used for optimal performance.
 

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I wish I had 93 readily available here in CA. If I had better fuel here, I'd be running higher boost on my Challenger!
 

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I wish I had 93 readily available here in CA. If I had better fuel here, I'd be running higher boost on my Challenger!
Around here, everyone that wants to run stupid levels of boost fills with corn...
 

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Around here, everyone that wants to run stupid levels of boost fills with corn...
I'm not quite there LOL. I'm running a stock Edelbrock E-force with an ATI 17% OD damper, putting me at just around 9 psi (seeing a little less pressure with the Hellcat cam in my Apache block, but the power is there). I would like to have pullied up at the blower, which would have put me at around 11 psi, but as configured I'm at the ragged edge of 91, so I couldn't go higher.
 

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Discussion Starter #12
I posted this article because this can be a very controversial subject. I got trapped into a long thread about this in a different forum. A lot of Jalopnik articles are kinda dumb, but this one actually has some good information for anyone who is running regular because it is the minimum acceptable. In the long run, perhaps you are not saving as much money as you think.
 

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Can't grasp the concept of putting lower octane gas in a high compression engine. On the other hand, I also can't grasp the concept of putting premium in a car that doesn't need it - a fool and their money are easily parted I guess.

One interesting development is the push for an unleaded aviation gas blend - those little Cessna and Pipers pulling banners up and down the beach are the last bastion of leaded gas and there's finally a for-real push to come up with an alternative. But a lot of the aviation piston engines are turbo charged or turbo-normalized for better performance at altitude and that means a high-octane blend. Currently 100LL (low lead) avgas is roughly equivalent to 100MON compared with 85 to 87 MON for mogas. If a functional unleaded blend is developed with anything like that octane, might be interesting...totally illegal from tax and environmental standpoint, but interesting....
 

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I posted this article because this can be a very controversial subject. I got trapped into a long thread about this in a different forum. A lot of Jalopnik articles are kinda dumb, but this one actually has some good information for anyone who is running regular because it is the minimum acceptable. In the long run, perhaps you are not saving as much money as you think.
On a technical level, one cannot argue with the benefits of higher octane fuel in high compression and forced induction engines. Heck even my 2011 Odyssey has more power. With a 10.5:1 compression ratio stock, kick A/C on high while towing a boat and drive red light to red light, and you'll feel the engine start pulling timing on 87 octane. Turbocharged engines kick up that effect to 11. Heat is the #1 enemy of small forced induction engines. On the Cruze, the cars would become **** near unsafe to drive because it would bog down and hesitate so much on acceleration off the line on 87. Every single summer, we get the same questions, "my car is bogging down, what's wrong with it?"

I've fought with people on this subject before, and I find that my opponents usually fail to understand how ECUs handle timing and knock on small forced induction engines.
 

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In the 124 Spider, I couldn't fathom running anything lower than 91 octane (US). Fortunately, we have 93 octane where I live, which is what I fill with. The dynamic compression produced in turbocharged engines requires that high octane fuel be used for optimal performance.
I live in a county with 91 (no ethanol) in the premium.
The county south of me has 93 (10% ethanol)
AND the shell station near the race track I AutoXed last weekend has 91 (0 E) & 93 (10% E)
What do I choose?
 

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I live in a county with 91 (no ethanol) in the premium.
The county south of me has 93 (10% ethanol)
AND the shell station near the race track I AutoXed last weekend has 91 (0 E) & 93 (10% E)
What do I choose?
Use the 93.
 

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In Europe FCA writes Super (95ROZ/91RON) as minimum specification in the manual (140hp and 170hp). As I wrote before, the 1,4l benefits from better fuel. I have made the comparison between 91RON (Super) and 94RON (Shell Vpower100) and you definitely feel the difference. More power in low rev. regions and smoother engine sound and run, also the idle mode is smoother. And about 0,5l (7%) less fuel consumption over 100km. Fuel is so fu..ing cheap in the US that I always would use 93RON.
Btw. the ECU needs time to adopt to a new fuel. About 22 heat up cycles or you remove battery for about 15min.

btw. with a OBD2 tool you can watch at the ignition timing and boost levels and see what happens during hot days or fun on twisted roads. ;)
 

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Discussion Starter #18
In Europe FCA writes Super (95ROZ/91RON) as minimum specification in the manual (140hp and 170hp). As I wrote before, the 1,4l benefits from better fuel. I have made the comparison between 91RON (Super) and 94RON (Shell Vpower100) and you definitely feel the difference. More power in low rev. regions and smoother engine sound and run, also the idle mode is smoother. And about 0,5l (7%) less fuel consumption over 100km. Fuel is so fu..ing cheap in the US that I always would use 93RON.
Btw. the ECU needs time to adopt to a new fuel. About 22 heat up cycles or you remove battery for about 15min.

btw. with a OBD2 tool you can watch at the ignition timing and boost levels and see what happens during hot days or fun on twisted roads. ;)
The US manual says Premium Unleaded 91 Octane or above (96 RON and above) Then it goes on: "Regular unleaded fuel with an octane rating from 87 to 90 (91 to 95 RON) can be used, but this will reduce performance slightly, such as reduced engine output and engine knocking."

My 500L's fuel filler door says "91 octane preferred, 87 octane acceptable, and my 500 pop says the same thing. (Or something like that, Same Turbo 1.4 engine as the 124 in the 500L, and a NA 1.4 in the 500.) I don't know if the 124 says the same thing on the fuel filler door, I don't have it yet. (2 or 3 weeks, it went on the boat may 31st)

93 octane is available here in New Hampshire, and that is all I use.
 

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Yup, Sunoco Ultra (93) here in NY. Only 2 cents/gal more than 91. Can't ever see 91 going in. Pretty simple math to me.


Gas is less than bottled water in the US for crikes sake. Drink less Poland Spring and treat your car to the proper fuel. Jeez.
 

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I live in a county with 91 (no ethanol) in the premium.
The county south of me has 93 (10% ethanol)
AND the shell station near the race track I AutoXed last weekend has 91 (0 E) & 93 (10% E)
What do I choose?
Can you send me some of that 0E for my lawnmower and snowblower. It's unobtainium out here.
 
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