pmartone

There seems to be no difference between the 2013 Honda Accord 3.5L V6 and the 2013 RDX 3.5L V6 engines, so why isn't the RDX specified to run on regular unleaded fuel to match the Honda Accord?
Thanks in advance for your replies.

Colorado Guy AF Ret.

The RDX IS OK to run on higher grade regular fuel. Premium is recommended.....not required by Acura. Overall....some on here prefer burning premium for better performance.
The engines in the Accord and RDX are very similar but, not exactly the same. I just traded a '12 Accord Cpe. V6. HP is slightly different...engine mapping is not quite the same, etc. Basically they are the same platform to start with.

pmartone

From what I have read, the 3.5L V6 engines on both the new Accord and new RDX indicate the same HP and torque and at the same rpms for each, so to me this seems like the same engine set-up, which is why I can't imagine there would be any problem using regular unleaded fuel in the RDX, since it is specified for the Accord.
Since I am not an expert, I welcome your thoughts; thanks.

Rocket_man

Previous debates on this topic suggest that if an engine will run properly on the lower octane fuel, the resulting loss of efficiency doesn't save you much if any money at the end of the tank. In other words you tend to get what you pay for. If you put the higher octane in you get slightly higher performance and the tank goes a little further.

I think it would be an interesting experiment to do. It shouldn't harm your engine. Put in 2 or 3 tanks of premium, meticulously record your distance traveled, do the math and see what mileage you got. Repeat for regular... compare the cost per miles and see if it was worth it.

It does feel nice though to grab the regular gas nozzle and not the premium nozzle.

KeithL

Under normal driving are you really loosing efficiency? If the engine is not pre-detonating then the timing will stay as is, thus MPG should not be impacted, only under load or high demand would it impact performance? GF has a TSX and we put mid grade in it and still get 25MPG around town

ipribadi

The difficulty here is trying to do a proper 93 vs 87 octane mpg comparison is very difficult.

All factors: gas brand, quality, driving route, wind, temperature, humidity, driving style, etc has to be the same. Even knowing that you have a certain octane # in your tank will affect how you drive.

One thing I want to try is just cruising on a decent length of road and observing the steady state real time mpg readout between the different octanes ... I'll see if I get the chance to do this

geocord

I tried that and saw about 1 mpg difference. It was on the same 90 mile route which I take once a week. Took it twice with a tank of regular and twice with a tank of premium. Weather probably wasn't a factor as I don't remember any heavy winds nor abnormal traffic.

Mike_TX

It's probably my imagination, but when I tried some lower-octane gas in mine it seemed to take the edge off the initial takeoff. One of the things I really enjoy about my RDX is the throttle tip-in, or how it takes off from a stop with only the tiniest bit of pressure on the gas pedal. It felt like it lost a little bit of that eagerness.

Again, maybe only my imagination.

rdxm

I assume it was 1mpg better with premium, right? What was the actual mileage? Around 27-28mpg? I'm just trying to figure out the difference in percentage.

geocord

Yeah, a little better with the premium but neglible. I didn't notice any difference in oooomph but then again I didn't really have a reason to goose it. I was going about 65mph the whole time and it was more like 28-29. I have an AWD. The overall readings on the regular for the whole tank was about 22. I run mostly midgrade now and am averaging about 23mpg on a 50/50 mix of light city/suburban freeway driving. I don't have to drive at rush hour so I rarely am in backed up traffic....just the normal traffic signals and stop signs.

Colorado Guy AF Ret.

As I stated before...the engines are NOT exactly alike. HP numbers are slightly different and I was told by an Acura/Honda engine expert...the computer mapping is different. But, you can burn non premium fuel, but, I don't....and if I did I'd put in 89 if it were available. But, the price difference factored over a year is just not that much. If you can afford the car you can afford the little extra in fuel for the benefit of a little bit snappier engine performance and a touch better fuel economy.

pmartone

Thank you for all of the helpful replies.
When I move from my 2010 Acura TL AWD Tech, to the new (2014) RDX AWD Tech, I will continue to use premium fuel.

danmangto

After running regular and premium for equal miles in my RDX. i dont notice a diff. Gas mileage is about the same. I avg 20 to 22 mpg in mixed driving. 50% stop and go and 50% highway. Performance is about the same. You are only going to notice a small diff with premium if you go to timed track. Lol. Knowone is going to be doing that with this family/commuter RDx. Otherwise in real world driving. 87 octane is very close if not similar to 91plus in the RDX. The old argument if you can afford the car you can afford the gas doesnt work. I can afford the 93. But it is not required on the RDX.

danmangto

Yes your imagination. I dont notice a diff on how my RDx takes off with 87 vs 93 octane. I do notice the nearly 50 cents a gallon savings at some stations around here diff. $6 or more per each fill up. My mileage is about the same.

Mike_TX

Maybe I just have a keener imagination than you. Retarded ignition timing COULD translate to a softer takeoff, though, as the ECU adjusts for it.

As for price, the increments around here are generally 16 cents, so the diff between 87 octane and the 91-93 Premium is 32 cents. Sometimes it's only 20 cents. Either way, if you used Regular gas exclusively and drove the "average" 12-15k miles a year, you'd save about $200 a year, or $16 a month, IF you maintained the same mpg. You just need to decide if that amount of savings is worth it to you.

Alkraut

This is a great forum, and I am a recent member.
Here is the engineering explanation of octane: It is my understanding that octane has to do with the amount of "anti-knock" additives in the fuel. "knock" or "pinging" is pre-detonation of the combustion chamber, in other words it is the ignition of the fuel-air mixture prior to the spark plug action. This condition is actually like a diesel where the compression and temperatures can ignite the fuel. The combustion chamber is designed to ignite from the plug tip and it rapidly goes across the chamber in a "flame front". When pre-ignition occurs, there will be two flame fronts, one from the pre-ignition, and one from the spark ignition. When they collide a "knock" will occur. Over time, this can damage the surface of the pistons. This typically can occur when the engine is pushed rapidly under load, and the ignition timing is "advanced" by the computer. You can here it in some engines when accelerating on a hill.

So what does octane do? it actually is an additive that decreases the volatility of the fuel and suppresses ignition. So high octane fuel is actually less volatile. So other than the need to suppress pre-ignition, high octane fuel is not an advantage. There are some varieties of "premium" fuel that contain additional additives like cleaners, so that is an advantage in those brands.

I have both a 2010 Accord V6 and and RDX. I have had the RDX for about a month and use regular grade fuel. No knock so far, but I am currently in Florida where there are no hills. When I return to upstate NY, I will see what happens. I think the reason that Acura engineers specify premium grade is that the combination of the 6th transmission speed and the ECC (cuts out 3 cylinders for ecconomy) creates a potential for knock when you hit the accelerator in those modes. As I mentioned, knock is bad, and over time can cause piston damage. So my recommendation is use the premium fuel if you feel more comfortable. If you use regular, and never here the pinging knock, you should be fine. Maybe mid-grade is the best of both worlds, and it is a bit less costly?

weather

*sigh*

de-pro

The price difference between 87 and 91 octane fuel where I am is around 15 cents a litter. $297 a year is the total saving if I used regular gasoline. This simply is not worth it. I used to put 87 octane fuel in my 05 Maxima. After a couple of years, she was pinging like crazy until I started using the 89 or 91 octane fuel. You may not notice a difference in performance in short term but you will see it in long term use of the vehicle. Again thats just my 2 cents based on past experience.

CoachRick

Well, we've certainly beat the heck out of this horse/power(figuratively, of course). I'll chime in again that I've never noticed a difference in performance or mileage using top-tier 87 in the RDX or any of our Volvos that carried the same 'recommendation' of higher octane. When fully loaded, towing(never) or climbing mountains, I would make sure the higher octane fuel got used. Otherwise, the difference in our two vehicles amounts to $650/yr or one car payment or the insurance premium for one vehicle for the year...nothing to sneeze at.

Might as well ask the engineers another related question:
Why do the manuals state that it will take 2-3 tanks of the 'different' octane for the engine to adjust? Seems the computer can adjust to avoid knocking almost instantaneously...why would it take more than a tank-full to realize the difference in changing octanes?

And for those who say they are using 'mid'-grade(89?), is that really any 'better' than 87 when the recommended is 91? Volvo used to recommend mid-grade for many of their turbos; but have switched over the years. Acura doesn't speak to 89 as a compromise octane rating(not that I've seen).

Mike_TX

Wow, Coach - you two really lay down some miles, don't you?

Rocketsfan

The new RLX, MDX and Accord use "EarthDreams" technology/engines. What that may mean outside of end-result performance, mileage, etc, I'm not completely sure. I was under the impression the RDX and Odyssey share the same engine, though.

Doubtit

Both are 3.5L displacement, both have same compression (10.5:1), and both use VCM technology. But HP, Torque, and redline are all higher in the RDX.

CoachRick

I'd love to cut back; but I can't do anything about the 1100 miles to our NC mountain house or DW's multiple trips to Madison/Jackson, MS(550 miles each way). Fortunately, there is no daily 'commute' involved; but DW is all over the city with her interior design 'stuff'. It was easier back in Atlanta when I lived 2.4 miles from the tennis center!

de-pro

I guess that's what the forums are all about (expression of opinions and past experiences) no matter how repetitive it may sound to some others....

supera

No,actually hp and tq are higher in the accord on reg gas.

rockstar143

iTrader: (6)

So 91 is only "recommended" on our Acuras? Interesting...saw a thing on the news about this.

Mike_TX

One of the selling points my sales guy tossed out was that the RDX can use regular gas. When I pointed out it doesn't really say that in the manual, he told me they all went to an orientation course on the new models and were told it was fine.

Now, that's hearsay, but interesting that the sales people were supposedly told that.

Vividsi

Colorado Guy AF Ret.

Again....Premium is "recommended".....NOT required. But, personally I would not use 87. 89 IF you have it available. For my '13 RDX I use 91 all the time. My choice.

dirvin

My salesguy said the same thing. I was tempted to go back and ask the service manager to see if he had the same answer (but I didn't).

rockstar143

iTrader: (6)

Sales tactic since gas prices went up and the need for "premium" isn't a selling point anymore. At some point, I bet they spin it to be like you're using the the better gas cause you have the better car.

J.

PS...around here...no 91...only 93.

Doubtit

I was responding to Rocketsfan's statement (right above mine) that he was under the impression the RDX and Odyssey share the same engine. HP in Odyssey is 248 and torque is 250. Guess I should have been clearer.

saxman48

This may be slightly off topic, but related to the price of premium. I filled up at a neighborhood Chevron station this past weekend. The display on the pump asked if I had a Safeway (grocery store) customer card. I do, and pressed 'yes' and then was prompted for my card number or phone number. I gave my phone number and was then told that I was 'awarded' a 10 cent/gal discount. Sure enough, the pump price was reduced by 10 cents/gal. Nice surprise, and made premium more reasonable.

This was the second time in a week, or so, that I was offered this award but the first time I tried having the pump read the Safeway card and it failed. I'm definitely sticking with Chevron while this award program continues.

justnspace

iTrader: (1)

be careful on what sub section you're in.
your acura REQUIRES premium as we have a higher enginecompression ratio than of the 2nd gen RDX.
I believe the 2nd gen RDX is sitting at 10:5 and so is the Accord.

Our TL's, however, have an Engine Compression Ratio of 11:1
and the higher octane is needed to prevent knock.

rockstar143

iTrader: (6)

Justin, in your various internet travels you've amassed quite a huge wealth of knowledge...thank you for sharing it with me.

Colorado Guy AF Ret.

Do you have a TL, and not an RDX??? IF so aren't you kind of confusing others on here talking about TL fuel needs....since this is the '13 RDX site?? Not ALL Acuras "require" premium. '13 RDX's it is not required.

KeithL

I believe the TL 3.7 and MDX are the only PREMIUM REQUIRED engines, not sure about the RLX.

rockstar143

iTrader: (6)

No, actually this an acura site and I'll post where I please.
I was asking questions not making statements so anyone that may have gotten confused deserved to be.

Colorado Guy AF Ret.

It's always easy to try and be a tough guy via blogs where you are hiding behind the internet. I simply asked you a question.

Yes, this is an Acura site....but, more specifically the '13 RDX portion....as there are portions for all the Acuras. Mixing them up is not a help....no matter what you feel like doing.

We are not on here to "deserve" to be confused by anyone, let alone you. So save your BS comments for those that care. I sure don't.

justnspace

iTrader: (1)

mr. colorado, i had saved him and reminded him to check the subsection.
what was the point of you bringing it back up after I corrected the mistake???

yes, this is just a question.