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post #1 of 11 (permalink) Old 08-05-05, 05:48 PM Thread Starter
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premium gasoline necessary?

Hi there. I'm a new member of this forum, and a new owner of an 04 MDX. The literature for these cars is clear that they require you to use 91 octane or higher, but I have not really been able to see why this a requirement rather than a recommendation.

Does anyone have the facts on this? If I put mid grade gas in my MDX, is something really bad going to happen, or is it just not going to perform at the levels described in the performance documents?

Thanks, Matt
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post #2 of 11 Old 08-05-05, 05:53 PM
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I would recommend you stick with 91 or higher. Feel free to ask Tim in our "ask the dealer" forum if you want it from the horse's mouth.

The issue I see lies with any future engine problems and Acura blaming you for not following the requirement that car has been using the right octane thereby allowing them to refuse giving you any work under warranty.
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post #3 of 11 Old 08-05-05, 07:10 PM
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The reason Acura recommends 91 octane for the MDX is because the engine compression ratio is 10.0:1. That's relatively high compression for a normally-aspirated engine, and high compression is a common cause for premature detonation. Lower octane fuels are more likely to experience premature detonation under high compression (i.e. knock). Your engine has knock sensors that will detect knock and try to prevent it, but to prevent knock it will retard the timing and/or change the fuel mixture/mapping as necessary. When this happens, the engine no longer performs at peak efficiency and your horsepower will suffer. Also, although knock sensors will save the engine from any longterm damage, they are meant for correcting the problem occasionally--they are not designed to prevent constant knock. So the solution is to run a higher octane, which is less prone to premature detonation.

In other words, you won't necessarily harm your engine by running 89 octane every now and then, it is not designed to operate efficiently with it constantly. To achieve the maximum horsepower available, it is recommended you run 91 octane all the time.


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post #4 of 11 Old 08-08-05, 12:10 PM
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Quote:
Originally Posted by hafid
The issue I see lies with any future engine problems and Acura blaming you for not following the requirement that car has been using the right octane thereby allowing them to refuse giving you any work under warranty.
Premium Octane 91 is NOT an Acura requirement; is is "merely" a recommendation. The owners manual clearly states that an octane LESS than 91 CAN be used, however a loss of performance may occur.

Unless you tow a trailer or drive at wide open throttle any horsepower loss well be trivial. Feel free to try any octane you want - it will absolutely NOT void your warranty.

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post #5 of 11 Old 08-09-05, 11:55 AM
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People always seem to ask similar questions about the TSX. With a compression ratio of 10.5:1 on the TSX, I would not and have not used anything less than 93 octane.

My thoughts are:

1) If Acura mentions "Premium Fuel" only, it's probably there for a reason. It's not like Acura is making money off of you or anybody buying premium fuel. With the TSX, I've heard people using regular gas, which killed their gas mileage and performance. Purpose defeated...

2) Those of us, who buy Acuras know that they aren't exactly the cheapest vehicles to buy. My point being, we can probably spend the extra couple of $$ to stick to the manufacturer's recommendations and be at peace of mind

D.
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post #6 of 11 Old 08-10-05, 09:30 AM
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Quote:
Originally Posted by bosox2004
My thoughts are:

1) If Acura mentions "Premium Fuel" only, it's probably there for a reason.
I would tend to agree with you IF that were indeed true. HOWEVER Acura never has said 91 Octane ONLY for the MDX. I am on MDX number two and know this for a fact! Acura says 91 Octane RECOMMENDED.

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post #7 of 11 Old 08-10-05, 04:51 PM
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Funny this should come up, my wife and I were test driving a new MDX last weekend and the sales man added "you can run lower grade fuels in the MDX and the computer will adjust for the fuel, it's a feature Acura added since fuel prices have risen".

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post #8 of 11 Old 08-11-05, 01:48 AM
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Wow! Great responses on the octane thing. I like the timeliness of this group. A testimonial about switching octane from a real life testamonial.
My brother in law drives a 2003 Touring Model. (I have a 2004). He's a daily driver from San Bernadino, CA to Redlands, CA. He decieded to switch to a cheeper octane gas of 89 when the recent inflation hit. He documented an average 16.9 a gallon on the trip computer. Gas has gone up 10 cents since then, he went back to 91 premium and he's now back to geting 19.5 pg.

Wow, not rocket science afterall.
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post #9 of 11 Old 09-02-05, 04:27 PM
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PING PING PING THAT WHAT A LOWER OCTANE FUEL DOES, I WOULD RECOMMEND THE 91 OCTANE ITS BETTER AND IT WILL BURN LONGER
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post #10 of 11 Old 09-06-05, 09:18 AM
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Quote:
Originally Posted by maximus
I WOULD RECOMMEND THE 91 OCTANE ITS BETTER AND IT WILL BURN LONGER


People read the manual - Premium is NOT required, but recommended for maximum power at WOT or towing.

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post #11 of 11 Old 03-18-19, 10:34 PM
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I have a quick quick will the if you have always ran in higher octane and still have the “which sounds to me the lifter needing adjustment” would that go away or best to get it in for adjustment?
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