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MDX requires 91 octane or above. No advantage to running anything higher than 91 though. The stations in this part of the US generally only carry 87, 89, & 93 so we have to run 93.
 

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No matter what car you own, the owners manual will tell you what octane to use. Octane levels have nothing to do with the purity or quality of the gasoline. The fuel system in your car is made to run on whichever grade the manual calls for. Running higher than reccomended is a waste of money and doens't improve mileage' while using lower than reccomended causes loss of performance and efficiency. These egines come with variable valve timing and are especially sensitive. Having to compensate for low grade gas causes premature wear and bad mileage.
 

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I usually stick with 91 octane Sam's or Costco gas depending on how long the lines are (most are across the street from each other in my town). I also travel and either Sams or Costco are my gas stops. The quality of the gas seems to be pretty consistent from Cali to FL (and they are always 5-20 cents cheaper compared to big name gas stations).
 

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MDX requires 91 octane or above. No advantage to running anything higher than 91 though. The stations in this part of the US generally only carry 87, 89, & 93 so we have to run 93.
Are you sure there is no advantage running higher than 91?
 

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^ Yes, There should be a compression bump or a F/I Tuning in order to burn 93 more effectively by the time your done you are better off with Race Gas..
91 is all you need with a stock or bolted-on MDX, if that isn´t available then 93 but you wont get any benefit from using it if you have the option of 91 vs 93.
 

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Here in Canada, most 91+ gas is also ethanol free. The motor might not benefit from the higher octane rating, but the lack of ethanol is certainly beneficial.
 

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^ Yes, There should be a compression bump or a F/I Tuning in order to burn 93 more effectively by the time your done you are better off with Race Gas..
91 is all you need with a stock or bolted-on MDX, if that isn´t available then 93 but you wont get any benefit from using it if you have the option of 91 vs 93.

FYI 94 +octane booster showed improvement 4hp to wheels on my STOCK MDX. Dyno was done some day, two hours apart, few runs..... So yes, higher is better, especially if it is hot outside or you are doing some towing, or driving in or driving in hilly areas...

In Chicago area Shell is da best and really not a fan of Costco gas. And I have to agree with Supertech... Costco is worst fuel I have tried. Last Place I would go is Costco to get my fuel for my MDX. If i would have Dodge Neon, yeah right, no problem, but not for my Acura ;)
 

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FYI 94 +octane booster showed improvement 4hp to wheels on my STOCK MDX. Dyno was done some day, two hours apart, few runs..... So yes, higher is better, especially if it is hot outside or you are doing some towing, or driving in or driving in hilly areas...

In Chicago area Shell is da best and really not a fan of Costco gas. And I have to agree with Supertech... Costco is worst fuel I have tried. Last Place I would go is Costco to get my fuel for my MDX. If i would have Dodge Neon, yeah right, no problem, but not for my Acura ;)
Costco gas actually uses more detergents than most gas stations out there in their additive packs! Plus with high turnover there is a lower chance for water in fuel.

Technically, using a higher octane CAN provide more power but in very limited circumstances. For example, its a 110 degree day and you've been driving for an hour or so. The engine is HEATSOAKED to where the ECU is cutting back on timing due to detonation with 91 octane. You fill up with 93 or 94 octane and MIGHT have a little bit more power as 93/94 is slightly more resistant to detonation than 91. This means the ECU can advance timing and allow for a more air which means a larger boom for more power. With that said, you might get as much as 5HP switching from 91 to 93/94. Remember that's about a 1% improvement if that with 300HP.

It does come with diminishing returns as the engine is only programmed to allow enough air for a car with 91 octane running at optimal conditions (no retard of timing).
 

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We stock up on 93 (long story, but I generally have at least 15-30 gal on hand that we use in a first in first out matter) so I use it in my Accord as well--it's strictly a matter of convenience. I've not noticed anything different on the Accord. I also use it in my lawn mower since it's on-hand and there it makes a world of difference! Pull starts on the second start w/o using the primer bulb. Never got that with the 87 octane.


Before we stocked up on the 93, I'd occasionally stick 89 in when I had at least half a tank ... mixes to around 91. Or, I'll use 89 Shell brand in an empty tank without any perceived differences. Got that tip from a Cincy Acura dealer.
 

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Hate to get into gas debate but as long as you're using top tier gas regardless of brand, your engine should run good long term and minimize deposits left with lower octane and/or low tier gas as they do not contain as much cleaning additives. Try talking to some fuel tanker trucks or following them around. It's not uncommon that the same trucks will deliver the same fuel to different branded gas stations.
 

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I've never had a need to add oil or fuel additives with my 3 Acura since sticking with syn Mobil 1 and Sam/Costco fuels for the last 10 yrs. No issues with power, no additional maint issues, and mpgs are consistent. I have about 340,000 miles between all three vehicles and plan to add around +70,000 miles each before trading any of them in.
 
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The only additive I use is a can of Seafoam every 6 months (Oil and Gas) or 1 Year in my Cars but I haven't done this in the MDX.

I did that on my TL-S + Syn Oil and well you will never guess this valvetrain has 215K on it:
 

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Costco gas actually uses more detergents than most gas stations out there in their additive packs! Plus with high turnover there is a lower chance for water in fuel.

Technically, using a higher octane CAN provide more power but in very limited circumstances. For example, its a 110 degree day and you've been driving for an hour or so. The engine is HEATSOAKED to where the ECU is cutting back on timing due to detonation with 91 octane. You fill up with 93 or 94 octane and MIGHT have a little bit more power as 93/94 is slightly more resistant to detonation than 91. This means the ECU can advance timing and allow for a more air which means a larger boom for more power. With that said, you might get as much as 5HP switching from 91 to 93/94. Remember that's about a 1% improvement if that with 300HP.

It does come with diminishing returns as the engine is only programmed to allow enough air for a car with 91 octane running at optimal conditions (no retard of timing).
On the other hand, opposite to your scenario, in a cold climate, perhaps higher octane is harder to ignite and can cause incomplete combustion resulting in slightly less power and carbon build up?
 

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On the other hand, opposite to your scenario, in a cold climate, perhaps higher octane is harder to ignite and can cause incomplete combustion resulting in slightly less power and carbon build up?
Not quite! The spark plugs are designed to provide enough energy to burn most of the fuel injected! In winter time, gas stations switch blends of gas causing fluctionations in MPG. In winter, ethanol in gasoline will hold onto more water making the "octane" higher, but the energy per gallon of fuel will be less.
 
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