Regular Vs. Premium Fuel

Scotty1981 said:
I've been told there are only two tanks at the stations for reg and prem fuels and the plus grade is a blend of both reg and premium, not sure if that is true but if so, it would be a good compromise of reg vs prem.
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Yes the ones that do mix have a metering valve to give to proper amount of mid grade fuel........
 
depending on the users geographic location, 91 octane could be their "premium", where other parts of the US have 93 as premium.
 
webby said:
depending on the users geographic location, 91 octane could be their "premium", where other parts of the US have 93 as premium.
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Right. Here in FL premium is usually 93, whereas 91 is rare but I do see some stations (rarely) with 91 octane premium as the top option. The typical FL gas station carries 87, 89, and 93. There's even a 7-eleven down the street from me that sells 87, 89, 91, and 93 ("super-premium"). 89 octane is pretty much always mid-grade here though, which is why I would say mid-grade ("plus") is not acceptable for our engines.
 
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Yeah ^...and as you travel west, it becomes next to impossible to find 93. Regular turns to 85 octane instead of 87 and so on.
 
webby said:
Yeah ^...and as you travel west, it becomes next to impossible to find 93. Regular turns to 85 octane instead of 87 and so on.
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Interesting. Had no idea, especially about the 85 octane. Regardless though, west coast mid-grade "plus" isn't okay either then, it's even worse.
 
I usually run 91 but have noticed the Mobil sells 93. Is the 93 worth the extra 15 cents a mile?
 
Brooksie 365 said:
I usually run 91 but have noticed the Mobil sells 93. Is the 93 worth the extra 15 cents a mile?
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What does your manual recommend ? If it's 91 then run 91.... The only time you might need a higher mix is if you suspect that the station you got it from has a slow turn over of traffic and that the ground gas isn't refreshed often enough for the octane to hold it's rating(old gas).
 
FooBird said:
Aw man you guys got me going today....

Brooksie, how much do you drive a month? You then have to ask yourself the question whether it's worth it to save that $3 per tank of gas, for me $15 per month by using an unrecommended fuel in the motor. Where does that $15/month trade-off come from, one less time going out to dinner, one less steak, three lattes in the month? The real problem is knocking. Yeah, the ECU in the Civic can correct for it, but I know from experience with my old Nissan Pathfinder, it DID NOT like anything less than 91 (yeah, it required premium, gotta love that VQ35) with both bad gas mileage and knocking. Do that for a long time and you could cause your engine to die at an early age, or cause no problems whatsoever. But with the high compression ratio on the Si, I'd personally just try to figure out where that extra $10-15 per month on what is a $200 gas bill is going to come from.
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Maybe I've got no right to post since I don't own an SI but we do have a 2011 Honda Accord EX-L coupe that should have a similar engine. What makes the 2.4L engine in the SI so different? Is the compression ratio a lot higher on the SI? The recommended fuel for our Accord is regular.
 
Internalaudit said:
Maybe I've got no right to post since I don't own an SI but we do have a 2011 Honda Accord EX-L coupe that should have a similar engine. What makes the 2.4L engine in the SI so different? Is the compression ratio a lot higher on the SI? The recommended fuel for our Accord is regular.
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Stolen from wikipedia:

K24Z7

  • Found in:
    • 2012 Honda Civic Si (US)
      • Displacement: 2,354 cc (143.6 cu in)
      • Bore and Stroke: 87 mm x 99 mm (3.43 x 3.90 inches)
      • Compression: 11.0:1
      • Power: 201 HP @ 7000 rpm
      • Torque: 170 lbs·ft @ 4400 rpm
      • Redline: 7000 rpm
      • Fuel Cutoff: 7200 rpm

K24Z3

  • Found in:
    • 2008+ Honda Accord LX-S/EX/EX-L trim models (CP2, CS1)
      • Displacement: 2,354 cc (143.6 cu in)
      • Bore and Stroke: 87 mm x 99 mm (3.43 x 3.90 inches)
      • Compression: 10.5:1
      • Power: 190 hp @ 7000 rpm
      • Torque: 162 lb·ft @ 4400 rpm
      • Redline: 7100 rpm
For those who may know, these engines do look extremely similar being K24Z series. I, too, am curious as to the differences in fuel requirements?
 
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The Si is at an 11.0:1 compression ratio versus 10.5:1. I'm sure the CR-V, which has the K24Z7 (same as Si) at 10.0:1 compression only requires regular, so the premium would be likely base tune and compression ratio.
 
Internalaudit said:
Maybe I've got no right to post since I don't own an SI but we do have a 2011 Honda Accord EX-L coupe that should have a similar engine. What makes the 2.4L engine in the SI so different? Is the compression ratio a lot higher on the SI? The recommended fuel for our Accord is regular.
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On the same exact page as you. I owned a 2003 accord with a k24 and it was regular. I understand compression and that mumbo jumbo. I just think its strange that 3-4 octane makes that big of a difference. I test diesel for c tane every single fuel tanker we get before offloaded which is 3 times a week. The amount of c tane varies in every load but 2-7 with in spec is fine with the diesels and that's 30-1 compression. Gas is a different world to me and me no likey.
 
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According to wiki
BP, Chevron, Cumberland Farms and other companies that acquired former Gulf operations continued to use the Gulf name through the early 1990s. This caused consumer confusion in the US retail market as the parent companies would not accept each other's credit cards. All former Gulf stations franchised by BP and Chevron in the United States have since been converted to those names.
 
webby said:
valero is exxon,... and exxon is top tier.
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Other than Valero purchasing one of ExxonMobil's refinery's in California along with 350 Exxon stations, I can't find any relation between the two companies. They even trade under different stock symbols.
 
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