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What about using octane booster with regular gas to compensate?
Pointless, imo. Just use the right grade of gas.
 
Purchasing a new 2017 mdx in 2 days. What about 89 octane from day one? 20 cents more is a heck of a lot better than 50 to 70 cents.
Thoughts
The 3rd gen MDX appears to be tuned differently than the others...less power than 2nd gen...I would use what is recommended...I am sure the MPG ratings and stated horsepower are based on recommended fuel.
 
Purchasing a new 2017 mdx in 2 days. What about 89 octane from day one? 20 cents more is a heck of a lot better than 50 to 70 cents.
Thoughts
:ghetto:

Acura recommends 91.

:lurk::lurk::lurk::lurk::lurk::lurk:

I don't understand the obsession some people have with cutting corners.

:9:

Next we'll see a thread where someone needs new brake pads and asks if they can substitute cheddar cheese, since Costco sells 2LB blocks for a good price.

Or what about using canola oil instead of Mobil 1? Canola is pretty slippery...

:2party:
 
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It appears the current Pilot and MDX have identical engines and transmissions. The MDX is rated at 290 hp and the Pilot at 280 hp. Both get the same rated mpg.

It appears in either vehicle, the primary benefit is the extra 10 hp- a 3.4% difference most people won't notice. I'd be willing to bet the Pilot makes 290 hp on premium, and the MDX makes 280 hp on regular.

However, under certain, very particular conditions, premium can get you a big mpg boost. This is because when it's working in 3-cyl mode, those cylinders are working pretty hard. Under certain conditions, premium may let it stay in 3-cyl mode when it might require all 6 cylinders using regular. That's my hypothesis on why some have noticed a big improvement in highway mpg using premium.

I live at high altitude, where the air pressure is lower, so 91 octane is a complete waste unless you're in a turbocharged car (god I wish this thing had a turbo). 89 or even 87 octane should give me all the performance this engine is capable of up here. However, because of the high altitude, regular here is only 85 octane. That make for quite a spread in cost for regular vs premium here- about 27%! I'm not paying 27% more for 3% more power! I suppose buying mid-grade is the ideal solution, but I can get premium at Costco for the same price as midgrade anywhere else. I think I'll run a few tanks of premium and a few tanks of regular to see if there's any mpg improvement at my conditions, but I think I'll make 100% of my potential power here by throwing in a third of a tank of premium every few tanks.

It's not about "cutting corners"- it's about cost benefit. Paying 27% more for 3% more power....if I'm lucky at my altitude...is not a good cost benefit tradeoff. It'd be like paying extra to water your plants with distilled water- a pointless waste of money.
 
These threads crack me up. Penny pinchers everywhere....I do like the cheese brake pad idea though...LMAO....

ME, I just burn the recommended fuel and don’t think twice...
 
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These threads crack me up. Penny pinchers everywhere....I do like the cheese brake pad idea though...LMAO....

ME, I just burn the recommended fuel and don’t think twice...
Penny pinchers? Why did you buy an MDX instead of an X5? Probably because it offered a better value to you. Using premium to avoid knock is a good value, but using it to increase power by 3% probably isn't a good value to many. At my altitude, it probably doesn't get me ANY extra power, so it's the equivalent of taking about $300 a year and just lighting it on fire. Why don't you light $300 on fire and then you can be critical of those who opt not to.
 
FYI:

Comparing the part numbers for 2017 MDX and 2017 Pilot shows the same part numbers for pistons, heads, and camshafts. Factory specs for MDX are 290HP, 267Tq, 11.5 compression ratio. Recommended fuel is 91 octane. For Pilot 280HP, 262Tq, 11.5 CR. and 87 octane.

I would bet that the only difference is a change of spark curve and possibly fueling map when the MDX knock sensor detects a knock. Probably just defaults to the same specs as the Pilot.

I also suspect that Acura tweaks their engine for premium fuel to get slightly better MPG numbers to make the EPA requirements for CAFE standards.
 
Penny pinchers? Why did you buy an MDX instead of an X5? Probably because it offered a better value to you. Using premium to avoid knock is a good value, but using it to increase power by 3% probably isn't a good value to many. At my altitude, it probably doesn't get me ANY extra power, so it's the equivalent of taking about $300 a year and just lighting it on fire. Why don't you light $300 on fire and then you can be critical of those who opt not to.

I am on my 2nd MDX because I have owned BMW's...that should tell you all you need to know right there. That said, burn what you like in your tank, I'll keep doing my best to burn what Acura recommends. It may be different on the 3rd gen...the 2nd gen I can tell a huge difference in the grades of fuel. A while back, nothing but regular was available...felt like I was dragging a boat anchor behind my 2011.
 
335i’s are nice driving cars....now we are way off track... :)
 
Whatever you do, don't try diesel. :)
 
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Right on! I totally agree, I was reading through and waiting for someone to bring up the compression ratio fact. Even if that is not what the OP meant, it certainly reads as if they had the two ideas confused.
Can you help with your thoughts and recommendation. I have a 2011 Fully loaded Acura MDX with 120,000 miles. Last summer it started burning fuel (I’ve always used premium fuel). Then this fall it started burning more oil. I’ve been using synthetic oil. Last week it was 2 litres low. I’d only driven about 2500 miles since the previous oil change. We changed the oil again (synthetic) and drove only 250 miles and he oil was low about 1.5 litres. Last week it started rattling, like metal. Metal.
What do you think is the issue?
Also This summer with the price of fuel so high (in Canada) I stated using only 89 octane fuel.
I read something that the issue could be minor, about emissions and the possibility of changing PCV valve.
Thank you in advance for your help! . It’s greatly appreciated
 
Can you help with your thoughts and recommendation. I have a 2011 Fully loaded Acura MDX with 120,000 miles. Last summer it started burning fuel (I’ve always used premium fuel). Then this fall it started burning more oil. I’ve been using synthetic oil. Last week it was 2 litres low. I’d only driven about 2500 miles since the previous oil change. We changed the oil again (synthetic) and drove only 250 miles and he oil was low about 1.5 litres. Last week it started rattling, like metal. Metal.
What do you think is the issue?
Also This summer with the price of fuel so high (in Canada) I stated using only 89 octane fuel.
I read something that the issue could be minor, about emissions and the possibility of changing PCV valve.
Thank you in advance for your help! . It’s greatly appreciated
the 2011 model is well-known to burn oil. You need to check your oil level regularly and keep topping it up.

The 2nd gen REQUIRES premium 91+, iirc. I wouldn't skimp on it.
 
You seem to make a large number of mistakes in this post, my guess is you have googled various things and just assume you know what you are talking about.

First, when running regular gas your timing if anything would advance not retard. retarding the timing would make it fire closer to TDC.
Second, yes RPM absolutely can change if pre detonation occurs, compression ratio stays the same, but the time the piston takes to travel has a large and direct effect on timing.
in other words an engine that pre detonates at high RPM might not as much or at all at low rpm.

Third, NO. high compression engines do not require premium. They MIGHT. mazda's would be a good example of this with up to 13:1 on regular gas just fine.

Lastly I have driving my 07 MDX in a variety of conditions while monitoring the timing and not only does the computer seem to sort it out quite well, but comparing regular to premium i see very little difference in Advance.

I'm by no means saying regular is necessary fine for the MDX (although my experience seems to show so), but at least get what you are saying correct.

I have heard engines before that require premium as a few of you put it, and the 2nd gen mdx is definitely not in that category, they run like crap. the mdx on the other hand, mine has 125,000 miles on it and during my 500 miles trip yesterday I averaged 25mpg and saw up to 30 on straights.

I'll let each person decide what they want to run themselves, for myself; if I'm seeing the same timing advance and the same gas mileage I'll keep running regular.
 
For what it’s worth - the NSX certified tech balked when I told him I only use 91+ and said “that’s not necessary” and I ONLY use 91+ and even still my throttle bottle was screwed.

So for me it didn’t seem to have a benefit but I don’t think I’ll switch at this point.
 
Hi!

Before you think this is another "pro using Regular" thread don't worry this isn't one. Instead I want to explain in a simple common man words why you should be using PREMIUM in the MDX or in fact in any High Compression Engine included the new Honda engines that only "Recommend" using Premium but does "Not Require it".

WARNING: If you don't like to Read then this is not for You.. But if you take your time to read through all this word fest you might learn something new and save money in the end. I had some free time and wanted to explain this in detail and in an easy to understand manner.



First the Basics:

What is Premium Gas? Premium is just a fancy way to call a high octane gasoline this means that premium is a gasoline with +91 octane.

What is Octane Rating? The Octane rating states how difficult it is to ignite the gasoline but you may think why would you need a Gasoline that is hard to ignite? Well this has to do with Compression.

What is Compression? Compression is when the Air and Fuel mixture is compressed in the combustion chamber this is calculated by the Stoichiometric ex: 11:1, 12:1, 13:1, 14:1 which means that the mixture of air and fuel is compressed a lot, This is referred as High Compression. Gasoline stoichiometric ratings for compression stop at 15:1 this is because only Gasolines with Higher Octane ratings (+100 Octane) can handle such compression. Since those gasolines aren't mainstream made engines use the most out of 91 and 93 octane which has a maximum stoichiometric of 14.5:1
These numbers refers to the amount of air vs gasoline that enters the combustion chamber, Having very little gasoline per air volume creates a Lean Mixture which in turns creates a LOT of heat.

The advanced stuff:

Honda Engines.
Honda since the very beginning is trying to make the most out of the displacement of the engines they make, by making high compression engines they can take the most out of the Combustion Stroke without using as much fuel. This is why most if not all their engine are High Compression Engines.

What about Regular?
Regular gasoline has an octane rating of 87 which means it can pre-ignite faster than Premium. Now that you know that High Compression engines run hotter this means that Regular fuel can pre-Ignite before the compression stroke ends.

What happens when the engine pre-Ignites?
Knocking, Ping or Detonation they are all results of pre-Ignite. What happens is that the engine is turning clockwise, the compression stroke builds up and when ignition occurs the piston is pushed downwards to keep the crankshaft turning clockwise. If Regular fuels pre-Ignites before the compression stroke can end it will fire up then the Piston is moving Upwards which then will be pushed Downwards causing the crankshaft to force it to turn counter-clockwise. This will cause SEVERE Damage to the Piston Rod which is pushing the piston upwards.

How come my Honda Engine can run Regular then if its High Compression Engine?
Since the dawn of Computer Controlled Ignition (PGM-FI) the ECU (Car computer) can control when to fire the spark plug, how much gasoline enters a combustion chamber and know when the engine is going to pre-Ignite. What the ECU will do in this scenario is simply put retard Ignition thus Timing.

What is Retard Timing?
Timing is referred to the exact moment the valves closes to start the compression & ignition stroke, the ECU can use the spark plug and timing (i-VTEC) to reduce the combustion chamber HEAT this is done by opening the exhaust valves sooner during the ignition stroke and by igniting the spark plug as late as possible (VTEC) so part of the combustion can exhaust sooner.

What are then the consequences of Retard Timing?
An Engine with Late Timing has more wear on the exhaust valves since its letting hotter combustion gasses pass through. This allows the combustion chamber to run cooler in order to prevent Regular gas from self-igniting but it also mean the Power Stroke is losing force thus the engine runs weaker and less efficient.

So why am I using Regular in a Honda Engine?
You might think you are "Saving Money" at the pump but in reality you have more wear and less MPGs using a Gasoline that technically is not made for High Compression Engines.

Why Honda then is Pushing "Not Required" in the 3rd Gen?
Simply put because of Demand and Supply.. People want to save money so if you are cross-shopping 2 cars and one demands premium and the other not then you have a higher chance of losing a sale.

What Honda did to make it able to run Regular on the 3rd Gen?
Honda engines can run Regular because the ECU can pull timing in order to run less efficient but safe. At this point you might be thinking Perhaps my 3rd gen MDX does not have a High Compression Engine! and you are wrong.. the J35Y5 has a compression of 11.5:1 making it a High Compression Engine.
This means it DOES require Premium because Regular is not meant to be used in such environment's. This means that every time you fill up with regular your engine is running less efficient and with less power than what Honda states.

But.. The car feels fine running Regular?
Of course it does silly we already made clear that the car can Pull Timing in order to run Regular!

But but.. People say I can run Regular if I don't WOT the car or Tow or Push the Car?
This is true again because the ECU will pull Timing so it doesn't really matter if you WOT (Wide Open Throttle = Floor It).

But but but.. People say that at lower RPMs Regular and Premium does not make a difference, it only matters at High RPM?
This is not only silly but completely untrue, The Engine was designed to run optimally with Premium in Mind this is becase again this is a High Compression engine they need to make out the most of the displacement and order to do that it needs Premium.

When the engine is running the ECU is trying to run the maximum compression it can, this is how the engine gets those lovely MPGs. So when you floor it the engine starts to hit an Air Volume Wall (Low RPMS) this is where VTEC kicks in, It makes the Intake Valves open longer and thus adding more Volume of Air which also needs more fuel to compensate and get that High Compression that makes all the power.. This means Compression ALWAYS STAYS HIGH! there is nothing like ohh yes when I am not flooring it, Regular is totally fine! again the engine runs LEAN as much as it cans because this is how you get MPGs. No one wants an engine using loads of fuel.

So if my Honda Engine is always trying to lean out to save fuel? What happens if I am Using Regular at low RPMS?
It happens the same as all the power band, the ECU will pull the timing like it or not. Lean = Hot = pre-Ignition Condition. So unless you make the engine try not to give the best MPGs there is no possible way to make the engine run efficient with Regular.

But if the ECU is preventing Knocking then its safe to use Regular Right?
But it is not normal to try to run the car in a less efficient way to save money. Just look it at this way.. If the engine needs 10oz of fuel for 1HP it means that using Regular the engine do 0.5HP for 10oz of fuel.. You are losing power which means you need more gas to move the car.. Honda states that the engine makes 290HP for the J35Y5 that is using PREMIUM! at low speed you might not feel the difference since the engine makes those 290HP at 6200RPM at normal Daily Driving RPM speeds its making way way less than that. So if the engine already has a low output using the gasoline it needs then using regular is making even LESS.

This requires to compensate by giving it more gas to do the same thing it can make with less gas. In the end you are NOT SAVING MONEY by using Regular on a High Compression Engine. Running Premium makes the engine run at its optimum performance giving you the HP you paid for, Making it last longer too.


This is the bottom line.. Its not what you THINK it is or how you THINK it works because nothing bad has happened..
This is Physics, Thermodynamics and Basic Mechanics..
High Compression NEEDS Higher Octane Fuel.
Unless Honda starts making engines with a sub 10.0:1 compression ratio then Regular is not the fuel you should be running on your +50,000 Dollar CUV.

This is why Low Compression Engines do not benefit from Higher Octane Fuel, They wont make enough heat to ignite Premium efficiently and thus might be ran less efficient running Premium than Regular a Good example is the HEMI 5.7L that states NOT TO USE PREMIUM BECAUSE IT WILL LOSE POWER.

PLEASE Do not said you are getting more MPGs out of Regular on a High Compression Engine this is Physically Impossible. You can run Regular on the car because ECUs are that smart and avoid a catastrophic failure but in no way shape or form a 11.5:1 Engine was made to be ran on Regular... Any engine that has that high of compression is pulling timing running Regular on daily basis.
Can you tell me why running the MDX with regular vs. premium seems to cause a huge amount of carbon to build up in the engine? What’s happening that causes that?
 
Hi!

Before you think this is another "pro using Regular" thread don't worry this isn't one. Instead I want to explain in a simple common man words why you should be using PREMIUM in the MDX or in fact in any High Compression Engine included the new Honda engines that only "Recommend" using Premium but does "Not Require it".

WARNING: If you don't like to Read then this is not for You.. But if you take your time to read through all this word fest you might learn something new and save money in the end. I had some free time and wanted to explain this in detail and in an easy to understand manner.



First the Basics:

What is Premium Gas? Premium is just a fancy way to call a high octane gasoline this means that premium is a gasoline with +91 octane.

What is Octane Rating? The Octane rating states how difficult it is to ignite the gasoline but you may think why would you need a Gasoline that is hard to ignite? Well this has to do with Compression.

What is Compression? Compression is when the Air and Fuel mixture is compressed in the combustion chamber this is calculated by the Stoichiometric ex: 11:1, 12:1, 13:1, 14:1 which means that the mixture of air and fuel is compressed a lot, This is referred as High Compression. Gasoline stoichiometric ratings for compression stop at 15:1 this is because only Gasolines with Higher Octane ratings (+100 Octane) can handle such compression. Since those gasolines aren't mainstream made engines use the most out of 91 and 93 octane which has a maximum stoichiometric of 14.5:1
These numbers refers to the amount of air vs gasoline that enters the combustion chamber, Having very little gasoline per air volume creates a Lean Mixture which in turns creates a LOT of heat.

The advanced stuff:

Honda Engines.
Honda since the very beginning is trying to make the most out of the displacement of the engines they make, by making high compression engines they can take the most out of the Combustion Stroke without using as much fuel. This is why most if not all their engine are High Compression Engines.

What about Regular?
Regular gasoline has an octane rating of 87 which means it can pre-ignite faster than Premium. Now that you know that High Compression engines run hotter this means that Regular fuel can pre-Ignite before the compression stroke ends.

What happens when the engine pre-Ignites?
Knocking, Ping or Detonation they are all results of pre-Ignite. What happens is that the engine is turning clockwise, the compression stroke builds up and when ignition occurs the piston is pushed downwards to keep the crankshaft turning clockwise. If Regular fuels pre-Ignites before the compression stroke can end it will fire up then the Piston is moving Upwards which then will be pushed Downwards causing the crankshaft to force it to turn counter-clockwise. This will cause SEVERE Damage to the Piston Rod which is pushing the piston upwards.

How come my Honda Engine can run Regular then if its High Compression Engine?
Since the dawn of Computer Controlled Ignition (PGM-FI) the ECU (Car computer) can control when to fire the spark plug, how much gasoline enters a combustion chamber and know when the engine is going to pre-Ignite. What the ECU will do in this scenario is simply put retard Ignition thus Timing.

What is Retard Timing?
Timing is referred to the exact moment the valves closes to start the compression & ignition stroke, the ECU can use the spark plug and timing (i-VTEC) to reduce the combustion chamber HEAT this is done by opening the exhaust valves sooner during the ignition stroke and by igniting the spark plug as late as possible (VTEC) so part of the combustion can exhaust sooner.

What are then the consequences of Retard Timing?
An Engine with Late Timing has more wear on the exhaust valves since its letting hotter combustion gasses pass through. This allows the combustion chamber to run cooler in order to prevent Regular gas from self-igniting but it also mean the Power Stroke is losing force thus the engine runs weaker and less efficient.

So why am I using Regular in a Honda Engine?
You might think you are "Saving Money" at the pump but in reality you have more wear and less MPGs using a Gasoline that technically is not made for High Compression Engines.

Why Honda then is Pushing "Not Required" in the 3rd Gen?
Simply put because of Demand and Supply.. People want to save money so if you are cross-shopping 2 cars and one demands premium and the other not then you have a higher chance of losing a sale.

What Honda did to make it able to run Regular on the 3rd Gen?
Honda engines can run Regular because the ECU can pull timing in order to run less efficient but safe. At this point you might be thinking Perhaps my 3rd gen MDX does not have a High Compression Engine! and you are wrong.. the J35Y5 has a compression of 11.5:1 making it a High Compression Engine.
This means it DOES require Premium because Regular is not meant to be used in such environment's. This means that every time you fill up with regular your engine is running less efficient and with less power than what Honda states.

But.. The car feels fine running Regular?
Of course it does silly we already made clear that the car can Pull Timing in order to run Regular!

But but.. People say I can run Regular if I don't WOT the car or Tow or Push the Car?
This is true again because the ECU will pull Timing so it doesn't really matter if you WOT (Wide Open Throttle = Floor It).

But but but.. People say that at lower RPMs Regular and Premium does not make a difference, it only matters at High RPM?
This is not only silly but completely untrue, The Engine was designed to run optimally with Premium in Mind this is becase again this is a High Compression engine they need to make out the most of the displacement and order to do that it needs Premium.

When the engine is running the ECU is trying to run the maximum compression it can, this is how the engine gets those lovely MPGs. So when you floor it the engine starts to hit an Air Volume Wall (Low RPMS) this is where VTEC kicks in, It makes the Intake Valves open longer and thus adding more Volume of Air which also needs more fuel to compensate and get that High Compression that makes all the power.. This means Compression ALWAYS STAYS HIGH! there is nothing like ohh yes when I am not flooring it, Regular is totally fine! again the engine runs LEAN as much as it cans because this is how you get MPGs. No one wants an engine using loads of fuel.

So if my Honda Engine is always trying to lean out to save fuel? What happens if I am Using Regular at low RPMS?
It happens the same as all the power band, the ECU will pull the timing like it or not. Lean = Hot = pre-Ignition Condition. So unless you make the engine try not to give the best MPGs there is no possible way to make the engine run efficient with Regular.

But if the ECU is preventing Knocking then its safe to use Regular Right?
But it is not normal to try to run the car in a less efficient way to save money. Just look it at this way.. If the engine needs 10oz of fuel for 1HP it means that using Regular the engine do 0.5HP for 10oz of fuel.. You are losing power which means you need more gas to move the car.. Honda states that the engine makes 290HP for the J35Y5 that is using PREMIUM! at low speed you might not feel the difference since the engine makes those 290HP at 6200RPM at normal Daily Driving RPM speeds its making way way less than that. So if the engine already has a low output using the gasoline it needs then using regular is making even LESS.

This requires to compensate by giving it more gas to do the same thing it can make with less gas. In the end you are NOT SAVING MONEY by using Regular on a High Compression Engine. Running Premium makes the engine run at its optimum performance giving you the HP you paid for, Making it last longer too.


This is the bottom line.. Its not what you THINK it is or how you THINK it works because nothing bad has happened..
This is Physics, Thermodynamics and Basic Mechanics..
High Compression NEEDS Higher Octane Fuel.
Unless Honda starts making engines with a sub 10.0:1 compression ratio then Regular is not the fuel you should be running on your +50,000 Dollar CUV.

This is why Low Compression Engines do not benefit from Higher Octane Fuel, They wont make enough heat to ignite Premium efficiently and thus might be ran less efficient running Premium than Regular a Good example is the HEMI 5.7L that states NOT TO USE PREMIUM BECAUSE IT WILL LOSE POWER.

PLEASE Do not said you are getting more MPGs out of Regular on a High Compression Engine this is Physically Impossible. You can run Regular on the car because ECUs are that smart and avoid a catastrophic failure but in no way shape or form a 11.5:1 Engine was made to be ran on Regular... Any engine that has that high of compression is pulling timing running Regular on daily basis.
I know I am late to this discussion.
I am doing my research on the 2008 MDX and learned of the 91 requirement. My favorite used car dealer just got one. I test drove it, loved it. Honda and Subaru are the only Asian makes I will buy. For some reason, I have a revulsion to Nissan & Toyota The rest just give me jitters, especially the H pretender.

I test drove it, loved it. I am set to pick it up today. It has 161K. I did feel like it wanted to give me more kick than it did. I thought it was a 4-cyl the way it drove. It drove like my Bride's 2014 Buick Encore. I drive a 2014 Jetta. That sewing machine (in size only) engine is second in my experience to the 97 BMW 528 I once owned.

Reading this article, I wonder in hindsight if the power was compromised by the grade of fuel. I am not paying $45K+ for it. I am not even paying $10K for it. However, whatever I pay, I want to maximize my miles per dollar paid. Reading the article and replies helps me understand that the elevated octane requirement is how the machine is designed to give me this.

I thank you for taking the time to write the article. I am going to review the manuals for the Encore and Jetta to make sure I am not starving them.
 
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