87, 89 or 91 octane?

87, 89 or 91 octane?

  • 87

    Votes: 69 88.5%

  • 89

    Votes: 3 3.8%

  • 91

    Votes: 6 7.7%
  • Total voters
    78
B

Bob-Loblaw

Member
:
2016 CX-5 GT
I've always driven trucks with poor mpg so never really considered anything above 87 octane fuel. However, I'm considering switching to 91 for this car. It would only be a few more bucks per fill up and when I think how often I spend a couple bucks w/o a second thought I'm thinking, "why not"? Any real world benefit to running higher octane or am I just throwing money away? What are you running? If you have a gas station preference, please list that as well.
 
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cybercruiser said:
My understanding is, since it's designed for 87, running 91 doesn't buy you anything.
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If that's the case then I suppose one could argue that any cost benefit from mpg efficiency is being negated at the pump when filling with higher octane (more expensive) fuel.
 
I tend to get better mpg with 93 octane but I will use 87 or 93. When I have the cruise control set at 90mph or higher with the AC on the engine seems to do better with premium fuel.
 
MidwestCX5 said:
I tend to get better mpg with 93 octane but I will use 87 or 93. When I have the cruise control set at 90mph or higher with the AC on the engine seems to do better with premium fuel.
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Cruise control set at 90 mph??!???! In Detroit, MI????? whoa....
 
We in Finland do not have such a low octane gasoline. I use mostly 98 octane in my CX5! Other option is 95 octane.
Markku
 
Different standards See: http://en.wikipedia.org/wiki/Octane_rating

Difference between RON, MON, and AKI

Because of the 8 to 12 octane number difference between RON and MON noted above, the AKI shown in Canada and the United States is 4 to 6 octane numbers lower than elsewhere in the world for the same fuel.
 
Do some research on-line from reliable resources. You'll find that higher octane does nothing for you if your car is designed for 87 octane. Yes, you'll get anecdotal stories from people who say that they get better mileage, but the science doesn't support that.
 
I just run 87 in my CX. My G35x requires premium and you can feel it if you drop 87 in that one. I assume the knock sensor is kicking in and taking out at least 20HP or so...
 
Bob-Loblaw said:
I've always driven trucks with poor mpg so never really considered anything above 87 octane fuel. However, I'm considering switching to 91 for this car. It would only be a few more bucks per fill up and when I think how often I spend a couple bucks w/o a second thought I'm thinking, "why not"? Any real world benefit to running higher octane or am I just throwing money away? What are you running? If you have a gas station preference, please list that as well.
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Don't waste your money by putting premium gas (93 AKI in Texas) into CX-5. The only benefit for you is it has more detergent. SkyActiv engine in US has lower compression ratio, 13:1, which is designed for using regular gas (87 AKI). If your CX-5 bought in any other places such as Finland where SkyActiv G engine is having 14:1 compression ratio, then premium gas (95~98 RON) is "recommended" to reach rated maximum horsepower which is approximately 5% more than US version.

Our CX-5 GT AWD has only 750 miles on it and we had pumped Shell regular twice. The MPG is 26.3 from computer and 25.8 calculated by distance/gallon with all city driving. We'll keep using top-tier gas such as Shell or Costco.
 
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The skyactiv engine re-engineered the cylinder structure and piston to be able to run on regular gas at a high compression ratio that would normally require premium gasoline. This is actually one of the great design features - that you DON"T have to use high octane fuel!
 
Ross_Richfield said:
The skyactiv engine re-engineered the cylinder structure and piston to be able to run on regular gas at a high compression ratio that would normally require premium gasoline. This is actually one of the great design features - that you DON"T have to use high octane fuel!
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Mazda's SkyActiv G gasoline engine uses advanced direct injection with very high 2900 psi injection pressure and six-hole injectors, the volcano-top pistons, and lengthy 4-2-1 exhaust header to overcome excessive heat build-up in the cylinders due to the high compression ratio. Cylinder block has been thinning out to reduce the weight. But it doesn't mean all SkyActiv G engines are designed to use regular gas. In fact, only in Northern America SkyActiv G engines run on regular gas due to lowered 13:1 compression ratio as the rest of the world is getting 14:1 ratio which should use premium gas with 5% more horse power. For example, SkyActiv G 2.0 in NA rated 155 hp at 6000 rpm and 150 lb-ft at 4000 rpm but 163 hp at 6000 rpm and 155 lb-ft at 4000 rpm for the rest of the world.
 
I sometimes confer with an expert who has a PhD in Mechanical Engineering and has been involved with the Society of Automotive Engineers. According to him, buying gas with a higher octane than your engine requires does nothing but line the pockets of the oil companies, who generally seem to be doing well enough without any gratuitous contributions from me.
 
Higher octane retards to fuel from igniting

If Your car was not designed for it and if itis operating correctly it will not do anything but actually hurt your performance

I run high-octane on my Mustang but it's got a supercharger and a custom-built engine. and a little bit different than this situation.

If your car is pinging then I might feel differently about it
 
I use 87 octane, but in my CX-5, running 91 octane makes a very noticeable differences in how the engine runs at low RPM and high load.

For example, with 91 octane the engine is perfectly happy driving up a steep driveway at ~1000RPM in 2nd gear.
Not so on 87 octane. With 87 the engine noticeably lugs at the same speed and requires a downshift to 1st gear.
 
piotrek, driving up a steep driveway at 1k in 2nd gear is probably not something you want to do often... That's 'lugging' it a bit, imho and harmful/stressful to the engine.
 
ramius said:
piotrek, driving up a steep driveway at 1k in 2nd gear is probably not something you want to do often... That's 'lugging' it a bit, imho and harmful/stressful to the engine.
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I don't always go up hills in 2nd, but when I do, I prefer 91 octane
 
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