Cablerat

Im sure this will open up a can o worms, but wanted to ask if everyone is filling their

Cablerat

Stupids ipad! And no edit feature...grrr

Anyway, are you filling premium 91+ or regular gas? What makes the rdx engine different from the odysessy, where the odysessy is good on regular?

Colorado Guy AF Ret.

This issue is sometimes kinda "obscure"...but, I have found that in many different types of vehicles....they will state to get the "best performance" use the premium fuel. Since my new RDX is waiting to arrive it is something that I will get straight with my Acura tech. friends. One thing I do know, living at altitude you can drop down to regular...such as 89 here in Colorado. My 87 octane vehicles I was able to run 85 here. Not an issue and OK'd by Honda.
My '12 Accord Cpe, with this very same engine that is in the '13 RDX, runs on 87 regular. Honda does not require premium. So....same engine but, telling us different things. I'll get it straight.....unless anyone else that has THE answer from Acura can chime in here. Thanks to all.

bh9712

Well, the manual says anything under 91 can cause pinging and anything under 87 can cause engine damage. Here in Denver, stations usually have 85, 87 and 91, so I'd be hesitant to use anything under mid-grade.

There are a lot of messages on the forums saying that going with higher octane will give you better mileage, but I haven't seen it.

I run the 91 - I figure $0.20/gallon x 16 gallons... What's another $3.20/fill up after paying for a "premium" car? I gas up about every 10 days - 2 weeks, so I'm really looking at about $100/year difference between low grade and premium fuel. That's less than I spend on car washes, so why risk it?

weather

bh9712....i agree with you 100%! That is how I look at it and my calculations are about the same as you. About 3$ a tank so if I use 4 tanks a months (which is on the pessimist side for me), then that is 12$ a month X 12 months a year, that is 126$ a year.

Peanuts if you ask me! I spend on average 80$ a month on Tim Horton coffee....All Canadian will know what I am talking it about when I say Tim Horton

hawkeye62

Hey, I paid around $40,000 for a luxury car. Why would I scrimp on fuel?

Jim

TLtrigirl

iTrader: (1)

the rdx engine is tuned differently than the odyssey.

long term wise, regular will cause the engine to lag and lead to poor MPGs which in turn will make you fill up more (spend more money on gas) vs premium fuel.

folks on the MDX side and the TL side have experimented with this.

and if you have to ask which fuel to use...maybe you should have considered a different vehicle. just sayin'

weather

Oups...I meant 144$ a month! No wonder my forecasts are never accurate...I can't do the math right *lmao*

charcoalwan

yup consider we spend $50-100 a week on coffee, the car have a cheaper hobby then we do , and in the long run , running regular may save you some now (cant say that as a saving, $120-200 a year) could cost you alot more in the future.

my MDX always runs shell 91's still get some engine ping, if i run esso92 it gets even worse.

weather

You spend 50-100$ a week on coffee? Did you say a WEEK? Wholly crap...you must be extremely fidgety

Cablerat

Didnt ask which fuel to use, asked which one others are using. I know from the tsx, i was getting better gas mileage with premium vs regular. But... U gotta wonder in some cars, that have the exact motor, same power output, yet require premium in the luxury model and regular in the lower equivalent.

weather

cablerat....I am far from an expert here so I may not be right at all but from what I read, the same engines can be tweaked differently and thus the reason for using the higher octane. I am not sure what Acura would gain from recommending to use supreme over regular as they don't have kick backs from the oil companies (or do they? hummm). I would argue that if they could get away from using supreme (or higher octane), it would even more appealing to some buyers....so the fact they don't seem to suggest there is a legit reason for it.

TLtrigirl

iTrader: (1)

the RDX engine is tuned for performance...the honda line is tuned for efficiency?

the RDX engine puts out more horsies and power than the pilot or the odyssey from what i can tell. maybe an engine expert can chime in here.

Cablerat

Definitely agree in the case of the RDX and most other engines: ECU tuning and engine timing can vary considerably (more air / fuel) resulting in greater piston compression and more HP. That can create more heat requiring a higher octane fuel to avoid pre-ignition. From tidbits of readings across many forums, I've read that it's NOT always a requirement even though some engine tuning has been implemented to push greater results. Automobile manufacturers may take the "safe than sorry" approach to recommend premium fuel to ensure the safety of the engine is maintained even though potential negative affects may be negligible, especially with the knock sensor being standard in most cars now.

Anyway, not worth any risk on the RDX to drop to a lower grade, however I'd love to find some credible information around this topic. Or even examples of engines dying due to 87 octane fuel vs premium on a factory luxury vehicle (non-turbo.)

I've heard plently of stories about people filling regular (87 oct) with zero issues for well over 200K. From a 07 Nissan Murano, 05 TSX to 98 - 00 GSRs, that just come to mind right now.

hawkeye62

This is an interesting discussion. I for one, would like to hear from a real engine expert. I do know that "knock" and "pre-ignition" are not the same thing. Pre-ignition is caused by a hot spot in the combustion chamber that ignites the fuel before the spark plug fires, and can cause severe damage to an engine. Knock happens when the spark plug fires and the combustion flame front compresses the remaining fuel until it ignites before the flame gets there. Knock will rarely damage an engine, but it will decrease performance. Knock is what you hear when you put the pedal to the metal and you are using regular in an engine tuned for premium.

One other thing, while the engines in the Pilot, Odyssey, Accord and RDX all look like the same engine, they all have DIFFERENT engine model numbers. So, there may be differences that are not obvious from the gross specs.

Regards, Jim

Colorado Guy AF Ret.

TLtrigirl.....just would like to disagree with your statement that the RDX is "tuned for performance and Honda's are tuned for efficiency." That's not entirely correct. If that is so..why did they work very hard to make the new RDX engine...which by the way is NOT a NEW engine...it's a Honda engine that has been around...and they tweaked it.. and their intent was to get more mpg out of this V6, by various methods, AND to have better performance than the previous 4 cyl. turbo engine?
Facts are...this "new" RDX engine gets very good mileage and is pretty quick. In today's automotive climate...engineers must work on efficiency also. And they did with the RDX. And so it goes for the Honda car line. They work to get great effciency, but, also, trying to get good/better performance each year.

I'll give you a great example. Do you consider the Corvette a car tuned for performance?? Of course it is. Did you know that Chevrolet also tuned this base engine to have great hwy fuel mileage when cruising...meaning if you don't have your foot in it all the time....it will deliver well over 20 mpg! Efficiency AND incredible performance from a great V8 engine putting out 435 hp.

This all exists because of the new CAFE standards from good 'ol Uncle Sam. The "Corporate Average Fuel Economy" standards that a car builder must meet across their entire line of vehicles. ALL their cars built...in total... must average a certain mpg number. So, any one vehicle that is just tuned for performance...will lower the companies CAFE numbers, and thus work toward keeping them from meeting the mandated numbers. So, it's in no car builders interests to NOT have efficiency in mind when tuning a new engine.
Yes, some are more efficient than others. But, it's turning out that the RDX is one of the most fuel efficient SUV's in it's class.

I can speak with some authority since my background is/was working with and teaching; gas engines, diesel engines, and turbine engines. For Boeing, prior McDonnell Douglas....I rode with and helped deliver the very last DC-10 jumbo jet sold. I taught the customer all of the major systems, including the engines.

To add to what others have mentioned about the new RDX engine....yes, there are different ECM mapping techniques that can be done as well as other minor tweaks, etc, to an engine that is basically the same but sold in another vehicle. Such as the Honda Accords's 3.5, 273 hp, 10.5 to 1 compression ratio engine, with the same torque specs. It is the RDX engine....with some tweaks. This gets us to the fuel "requirement" issue. I'm still working on why Acura wants/prefers 91 premium and the Honda badged engine requires/prefers 87. When I get the definitive answer I will share here.

For me...and this is for those that say what the heck...pay the extra for premium....it's not about the money. I can afford the extra. But, I look at it from an engineers mindset. Why....exactly why is it necessary. Just something I have to find out for myself. It never was about the cost for me. It's the "technical need" for premium vs the "why." That's all.

And to...hawkeye62......yes, "pinging" will eventually cause engine damage...faster if the pinging is pronounced. That's just a fact. Even though "knock sensors" are used....damage can and will occur if the octane grade "needed" by any particular engine is way below what the engineers deemed necessary.

You can "fact check" that anywhere...with credible sources, and you will find you don't have to trust me...but, trust the facts and reality of this engine issue on fuel. Pinging as most know it...has been around forever. An improper burning of fuel under compression leads to engine damage. That's just a cold hard fact.

Best wishes to all. This is a great web site. Keep up the good work.

justnspace

iTrader: (1)

Colorado guy, What is the engine compression ratio for the new RDX?
could it be higher than the accords, 10.5:1?
could that explain the premium over reg. fuel?

as you said, "pinging is the death of an engine" (paraphrased)

sixsixfour

the 2013 RDX runs a 10.5:1 compression ratio. not high by typical Honda standards to require premium.

frankly a much higher octane would burn more evenly, and have less a likelihood of pre-detonation (knock or ping) compared to lower grade gasoline.

the higher the compression ratio in an engine, the higher the internal pressures and heat, and therefore, a low-octane fuel would ignite (or pre-detonate) long before the spark plug fires. repeated instances of this is what causes engine damage. all a knock sensor would do is retard timing and run more rich (inject more fuel into the air:fuel mix to cool off the mixture), thereby lowering the intake charge temperature, and preventing knock. the downside to this is that your fuel economy goes out the window.

higher octane gasoline would allow the engine to operate at or near its peak performance envelope without having to retard timing and use more fuel to prevent knock. so if that engine is designed to output a certain HP amount and yield 30MPG, you are more likely to attain that HP figure and mileage using premium fuel than you are by using regular grade fuel.

justnspace

iTrader: (1)

^right.

I remember reading a thread by I hate cars, saying that he monitored knock.
Mixing 100 octane and 93 to make about 96 stopped the knock.
but this is with our high compression TL. 11:1

sixsixfour

yeah. I put 100 octane to mix with 91 during the really hot summer months. intake air is already warmer than it usually is, and the car literally struggles to get to speed under full load (a/c, four people). but when you put about 3-4 gallons of 100 mixed with 91 and reset the ECU, the car comes alive even in hot weather.

knock does its most damage when the piston is in the upward travel of the combustion cycle. when the fuel detonates while the piston is moving up, thats when you have the possibility of bending the rod - especially if that happens at WOT at high engine speeds (excess of 5000 rpm). imagine something preventing the crank from spinning at 5000 rpm and you have the recipe for disaster. the rod is gonna bend at best and the crank will crack at worst.

TLtrigirl

iTrader: (1)

@colorado-thanks for the clarification. i was making a generalization, but thanks.

my point was that hondas in general are geared towards the masses who could probably care less about HP. they want a car that gets great fuel efficiency and it reliable. folks looking at the acura line are probably a little more performance oriented first prior to being feul efficient (and i know the govt regulations are pushing for more fuel efficiency so acura is looking for that too while still trying to balance the high performance). then again with the new ILX...you lose some of that fun factor (a completely differnt discussion entirely). and i am well aware that the RDX has the same engine that is used in the honda line up with a few "tweaks" henced tuned differently.

again...thanks for the clarification.

damaged442

Based on the 11:1 compression ratio, I will run 93 octane. Over the long run, the price difference is not substantial. I have seen no benefit from running a lower octane.

mrgold35

I think Acura is recommending 91 Octane because of the cylinder deactivation. Having the 2013 RDX loaded down with people, gear, and fuel would put the curb weight at 4800-5200lbs PLUS the possibility of towing 1500lbs. I don't think the 2013 RDX will like regular fuel if cylinder deactivation kicks in under those conditions.

Acura is the performance branch of the Honda automotive group. They have to add a few more HP and recommend 91 octane to give folks the feeling of a premium name plate. I rather run with 91 octane because you never know when you need all 273 hp.

sixsixfour

spec shows the 2013 RDX curb weight of about roughly 3700lbs. for comparison, the base Odyssey which also uses cylinder deactivation tips the scales at 4337lbs. so the weight of the vehicle under full load is not likely the reason behind premium fuel as a requirement, as the Odyssey runs on regular and has variable cylinder management.

besides, cylinder deactivation is designed to activate under steady low rpm situations (i.e.) cruising, so any extra weight on the vehicle would kick in the extra cylinders on demand. the RDX wont run on 3 cylinders under full load anyway. if you tow something on it, it is unlikely the cylinder deactivation feature would even kick in.

Colorado Guy AF Ret.

Hey sixsixfour......great job on answering others on this engine fuel issue!
Cylinder deactivtion is NOT the reason for 91 octane fuel...for those that think that. sixsixfour is right.
Again...for those that missed it.....I have "basically" the same engine in my '12 Acccord Cpe. I only have to use 87 octane. Same horsepower, same 10.5 compression ratio, etc. Just some tweaks to the timing is what I've found out so far why the RDX might be required to use 91 octane.

To all that answered some of my postings. You guys are all pretty great when it comes to this forum. We seem to be able to work things out...and work through various subject matter without someone getting their nose out of joint. When I was on one of the Honda forums....well, let's just say they are mostly neanderthals and always seem ready to pick a fight. I got tired of that pretty quickly.

hawkeye62

I am re-posting this here because it seems to fit here better. One other thing I have learned is that although all of these engines appear to have the same specs, they all have different Honda part numbers. So, there may be differences not apparent from the gross specs.

The RDX, Accord, Pilot and Odyssey all appear to have the same 3.5 liter V-6. The Accord and RDX have the lowest curb weight, highest HP and the highest red line (6,800 RPM). I suspect the differences between the engines is the tuning of the Variable Valve Timing. But, I don't see why the RDX requires premium fuel. If the Accord can deliver 271 HP at 6,000-6,200 RPM on regular, the RDX should be able to deliver it's rated 273 HP at 6,300 RPM on regular. Probably has more to do with marketing than technical issues.

In any case I would very much like to know the answer to why Acura recommends (not requires) premium and Honda recommends regular.

Regards, Jim

bh9712

Is it possible that it was an economic decision? The RDX has an extra year and 10,000 miles on the powertrain warranty. Maybe Honda figures using premium fuel will decrease claims in that last year?

Or maybe if they recommended premium for Accord/Odyssey, the lost sales would have more impact than potential warranty claims where Acura buyers may be less put off by it.

Just a thought since it isn't clear that it is a performance issue.

gbriank

This discussion has been beaten to death over on the Second Generation RL board. My experience with my 2005 RL was that regular unleaded yielded about a 2-3mpg drop in economy (70% City, 30% Highway). I do not know of any engine damage (as the ECU will "adapt" the spark, air intake and fuel ratios), but performance and fuel economy had suffered. I went back to Premium and everything was back to normal.

Colorado Guy AF Ret.

gbriank....is right. This subject has been battered around quite a lot here. But, then again, it is one of he "hottest" topics no matter what forum you go to.

Let's look at what we DO KNOW. Acura...RECOMMENDS 91 premium. They DO NOT REQUIRE it. That's their words in their RDX Owner's Manual. That means that if you are where you can buy 89 octane fuel then you would be good to go. The computer does adjust and compensate.

In another thread I was wrong about Colorado. I said we didn't have 89 octane. We do. We don't have 91. That's due to the altitude. Don't need the highest octane made. I'm as sure as Grant is buried in Grant's tomb.....Uhhh...he is isn't he???.......that I can safely burn 89 octane in my new RDX. How do I know....easy....'cause I can't buy 91! LOL!!

But, even if I had 91 and 89 available, I am confident that 89 would burn just fine and the ECM would easily compensate. That was the case for my Honda engines. After personally speaking with Regional Service Engineers...they admitted as much. At corporate levels they don't like to say much about this subject area. They are like politicians...they talk "around" the question and you never get a straight answer.

mrgold35

Is the 2013 RDX 3.5L engine a de-tuned version of the current TSX/TL 11.2 compression engine OR the tuned up version of the Odyssey/Pilot/Ridgeline/Accord engine? Dropping the compression from 11.2 down to 10.5 might produce 273hp/251TQ and provide the option for reg/mid/premium fuel in the process (add in different cam profile, ECU calibration, intake/exhaust, combustion chamber design, valve design, cylinder head design, etc...).

Are we saying the RDX engine IS the same as the Accord because the HP/TQ number are so close? I don't know one way or the other; but, I'm leaning toward Acura keeping everything in the family and using a de-tuned TL/TSX engine. Give me hope they can up the power in the future for a Type-S sh-awd model down the road (compete against the Lexus RX F-Sport).

I would like to see the dyno on this engine compared to the TL, TSX and Accord 3.5L; I think it would be interesting.

Colorado Guy AF Ret.

In essence...all the 3.5 Honda/Acura engines use a "base" engine and then tune from there. It just so happens that my '12 Accord Cpe. engine has almost the exact same specs. I'm sure the RDX's timing is bumped slightly and some very minor tweaks to "recommend 91 vs. my Accord engine recommends 87."
Personally I don't believe that any of these engines are "exactlly alike" but, their ECM's are tuned for that particular vehicles useage, etc.
But, some of them, like my Accord engine and the RDX are so very close to being the same engine. It's in Honda Corps best economic interests to have them very similar with just tuning tweaks as needed.

One Honda Corp example. The Acura TSX, 4 cyl. engine is rated at 201 hp. The almost same engine in the Accord...there are (2)...on is rated 171 hp and the other 190. They are based on the same basic engine, just tuned to the need of the application.
I had the 190 hp 4 cyl in an '08 Accord Cpe. It was a sweet 4 cyl engine. Pulled hard when the RPM's started cranking. Felt every bit as strong as the TSX's 4 cyl. engine. The TSX required, I believe, 91 premium....could be recommends.....but, my Accord was good to go on 87 octane. And again, it pulled very hard and felt as strong as the TSX. And, it gave incredible fuel mileage, esp. on a trip. I was amazed.

TLtrigirl

iTrader: (1)

i was just at my dealer. and one of the salesman had approached me after he saw me playing in the RDX in their showroom. he said that the RDX is the only acura that can take regular. i started talking about how the engine is the same one used in a few of the honda lineup, but the RDX is tuned slightly differently. i think that's where i lost him b/c that's where he started mentioning that it had more HP than the hondas. he didnt' say much else after that.

now i haven't seen what the owner's manual states, but this is from the sales guy at my dealer. not saying all sales guys know all the intimate details of the cars, but this is what he said.

weather

^^^ So after sitting and checking it out in person, what are your thoughts on the RDX? I am still a HUGE fan of the MDX and I was driving around town this evening and saw a white 2012 MDX coming towards me and OMG that vehicle is sooooo nice! I can't see how Acura will be able to improve on such a well executed vehicle. Too bad it was much bigger than what I needed....

Colorado Guy AF Ret.

TLtrigirl....As I stated earlier....the TSX engine has more horsepower, but, is basically the same engine as the Accord's 190 hp version.
My Accord Cpe 3.5 V6 is rated at 271 hp at 6,200 rpm, and 254 lb ft of torque at 5,000 rpm.
Compare that to the RDX engine: 273 hp at 6,200 rpm, and 251 lb ft. of torque at 5,000 rpm. They both have 10.5 to 1 compression ratio and they red line at 6,800 rpm
I don't know how much closer you can get. They are tuned "slightly" differently, but, not by very much.

First, of all, most every sales person I've ever met knew next to nothing about the technical aspects of the vehicles they were selling. Heck, many don't know much about the cars/SUV's themselves...only what they memorized from a book or watching/listening to someone else. I've always known more than a salesman, and have often times taught them something about their own vehicle they were trying to sell me. Most aren't true auto sales professionals. Many have sold other things...non auto related. I was told by one guy....he sold refrigerators and now he's selling cars...he said, "selling is selling." Yeah right!!
Now, technically your guy was right....the RDX is listed at.....2 hp....more than my Honda badged engine. But, the RDX has slightly less torque. Trust me...that will never be noticed or felt. My engine background tells me those figures fall within the "margin of error."

I doubt he knew the true figures or knew anything about the Accord's 3.5 engine. I'd bet my dog on that....and I love my dog!!!

Now, nothing is all encompassing. Yes, I know we can all find a handfull of car sales folks that know a lot about what they are selling. But, not that many.

One of the top sales guys at an Acura dealer I visited didn't know the RDX tail gate can be opened by hand...meaning it can open and close without using the electric motor closing and opening it. I showed him where the manual unlock and lift lever was!!
Most don't take the time to learn the vehicle. They just want to get you excited about it and sell it to you and move on to the next potential sale.

hawkeye62

pitaE=TLtrigirl;13833681]i was just at my dealer. and one of the salesman had approached me after he saw me playing in the RDX in their showroom. he said that the RDX is the only acura that can take regular. i started talking about how the engine is the same one used in a few of the honda lineup, but the RDX is tuned slightly differently. i think that's where i lost him b/c that's where he started mentioning that it had more HP than the hondas. he didnt' say much else after that.

now i haven't seen what the owner's manual states, but this is from the sales guy at my dealer. not saying all sales guys know all the intimate details of the cars, but this is what he said.[/QUOTE]

The manual says recommended, not required. So, I am sure that the ECM will compensate for regular fuel, with some hit on performance and/or gas milage. BUT, I don't care about a few cents a mile more for premium. What I would like to know is WHY does Acura recommend premium. I think it is just a marketing strategy, luxury vehicle, luxury fuel.

Regards, Jim

TLtrigirl

iTrader: (1)

let me see if i can pick a brain over in the service dept next time i'm over there. the sales guys aren't really that big of gear heads as the guys who work on cars all day.

krazydan19

i have a 2005 tsx since had 28k i run 91 or better every tank have 102k now and mobil one every 5k. getting 29 mpg on long trips driving to fast. and 23 mpg during my normal work week driving again driving to hard..

also a 2010 RDx since she had 9k same 91 plus every time with 32k now and mobil one every 5k. was getting 22 mpg in the mtns everyday work week gettin 15mpg

both have hondata i dont know love them both and they ask for the good stuff so thats what they get. what do you guys think of the 2013 rdx? new motor? alll that stuff ?

VegasSmitty

I asked the dealer when I went back in to pick up some paperwork, he said to putting in regular would be fine. When leaving I went around back to the repair area and asked a mechanic, he said the same thing.

Colorado Guy AF Ret.

I'm not mistaken....your RDX REQUIRES premium fuel for that turbo engine. Check your manual and see what word they used...Required or Recommended????

The '13 RDX it is Recommended...not required. But, you should use no less than 89 octane. The computer will get used to it and make the adjustments. But, as many have said, if you can afford the RDX, then you can afford the extra fuel costs by burning Premium.

At altitudes you can normally run a lower octane, but, I don't have 89 available. I have 87 and 91. So, I burn 91....I probably would anyway.

Mikey Dallas

I have been burning 93. I just think the extra twenty cents a gallon is worth it for my baby. Anyway, the engine just sounds so sweet when you give it what it wants...