Mid-grade gas - do you?

[BerserkerCatSplat]

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For real? Ive been running 91 minimum in my Grand Cherokee. This thread just saved me a few bucks...

Yep, I checked a 2017 owner's manual just in case and they still recommend 89 but allow 87.

This engine is designed to meet all emissions regulations and provide satisfactory fuel economy and performance when using high-quality unleaded gasoline having an octane range of 87 to 89 as specified by the (R+M)/2 method. The use of 89 octane “Plus” gasoline is recommended for optimum performance and fuel economy.

I run 87 in the winter but I switch to a 91 tune in summer.

[triplep]

I usually fill up the Accord with 91 as 87 gives me engine knock. However, if I am going to do a lot of highway driving say going over to B.C. I will use 89 as it seems to work really well. In the city unfortunately 89 will at times produce engine knock.

[Tik-Tok]

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For real? Ive been running 91 minimum in my Grand Cherokee. This thread just saved me a few bucks...

You can probably save a few more as at our altitude, you don't need as high of octane. So if they recommend 89, 87 should suffice.

[speedog]

So if the mixing is done at the pump then what guarantee does one have of the level of the octane in the mid grade?

[killramos]

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So if the mixing is done at the pump then what guarantee does one have of the level of the octane in the mid grade?

Those fancy government calibration stickers are a good start

I would be way more concerned about what’s in the fuel than how they mix it lol

[speedog]

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Those fancy government calibration stickers are a good start

I would be way more concerned about what’s in the fuel than how they mix it lol

I do know that pumps are checked for actual volumes being dispensed versus what the pumps say is being dispensed but are they actually checked too see if the mixed midgrade actually meets the stated octane numbers?

[ExtraSlow]

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I do know that pumps are checked for actual volumes being dispensed versus what the pumps say is being dispensed but are they actually checked too see if the mixed midgrade actually meets the stated octane numbers?

They probably don't check octane for any grade at the pump, but they do check volumes of each grade, so if you trust that 87 and 91 are correct a 50/50 mix of 91 and 87 will be 89 by definition.

[speedog]

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They probably don't check octane for any grade at the pump, but they do check volumes of each grade, so if you trust that 87 and 91 are correct a 50/50 mix of 91 and 87 will be 89 by definition.

And therein lies the problem, are pumps being checked for the midgrade mixture ratios? Any searching I've done doesn't seem to mention any testing of midgrade octane levels at the pump or any octane levels at the pump, 87 and 91 are regulated at the source (manufacturer) but what of midgrade? Does a consumer really know what they're getting in a midgrade fuel?

[killramos]

Better just buy 91 JIC

Sounds like a water in the gas type conspiracy theory

[ExtraSlow]

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And therein lies the problem, are pumps being checked for the midgrade mixture ratios? Any searching I've done doesn't seem to mention any testing of midgrade octane levels at the pump or any octane levels at the pump, 87 and 91 are regulated at the source (manufacturer) but what of midgrade? Does a consumer really know what they're getting in a midgrade fuel?

Maybe I didn't explain myself. They don't need to test octane at pump if they test that the pump is mixing correct volume ratio of 91 and 87. I think they do test that volume ratio.

[speedog]

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Maybe I didn't explain myself. They don't need to test octane at pump if they test that the pump is mixing correct volume ratio of 91 and 87. I think they do test that volume ratio.

But do they actually test/calibrate that ratio? I can not find anything that verifies this is done.

[ExtraSlow]

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But do they actually test/calibrate that ratio? I can not find anything that verifies this is done.

I'll bet they do, but I can't prove it.

[Super_Geo]

F30 328i says minimum octane 89, and that's what I use.

[DboyNismo]

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High compression N/A?

Ultimately it just depends on what fuel specs the engine was designed for.

Apparently the 2ZZ in the Corolla can run on 89 no problem - I've always used the recommended 91 as it is a high compression engine.

Another note, any subie owners run co-op 91? I've only used Shell due to the non-ethanol blend, but I read below that Co-op in Calgary also has no ethanol. Any downsides?

[killramos]

I wouldn’t go with “can run” specs.

I’m sure my car “can run” on dirty 85 from Idaho, doesn’t make it a good idea.

[Misterman]

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So if the mixing is done at the pump then what guarantee does one have of the level of the octane in the mid grade?

You're guaranteed a minimum of 89 as advertised on the pump. The 87 and 91 it mixes from are both guaranteed to be that at a minimum, if either option is over its minimum requirements as they often are, then you'll get better than 89 out of the pump. If you're worried about accuracy of mixing, well that stuff is pretty regulated. If a station was found to be mixing too much 87 in the mid grade and underselling it, they'd be in trouble.

[speedog]

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You're guaranteed a minimum of 89 as advertised on the pump. The 87 and 91 it mixes from are both guaranteed to be that at a minimum, if either option is over its minimum requirements as they often are, then you'll get better than 89 out of the pump. If you're worried about accuracy of mixing, well that stuff is pretty regulated. If a station was found to be mixing too much 87 in the mid grade and underselling it, they'd be in trouble.

You could very well be correct but I am surprised that there doesn't seem to be any information out there from a regulating/standards body that details/addresses this - one can find almost anything on the web but this is like a ghost.

[Aleks]

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I wouldn’t go with “can run” specs.

I’m sure my car “can run” on dirty 85 from Idaho, doesn’t make it a good idea.

Doesn't 85 exist in Colorado because some places there are so high up that 87 isn't needed for a lot of engines even if they recommend 87?

I bet a lot of cars here could use 89 or 87 just fine on a lot of days with no knock even if their cars recommend 91 for "optimum" performance.

[Tik-Tok]

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Doesn't 85 exist in Colorado because some places there are so high up that 87 isn't needed for a lot of engines even if they recommend 87?

I bet a lot of cars here could use 89 or 87 just fine on a lot of days with no knock even if their cars recommend 91 for "optimum" performance.

Not just Colorado, go to Montana and you'll see plenty of 85 at the pumps. It's surprising that with the number of professional O&G engineers on Beyond, not a lot know much about their own end product.

[killramos]

Yea, even in the oil business, most peoples “end product” here is Crude.

Not really a fair statement, that’s an entirely different business.

I also have next to no knowledge of plastic for that matter.