I have a 2015 RDX which I have been putting in premium fuel since brand new. It makes me mad that premium can be up to 55 cents more a gallon where in live in PA. I did a little research and noticed the new Honda Pilot has a very similar engine to the RDX with an even higher compression ratio (11.5:1 compared to 10.5:1 for RDX), yet honda recommends regular fuel for the Pilot, but premium for the RDX. How is this even possible? Wouldn't the higher compression ratio engine (Pilot) require premium more than the lower one (RDX)?

 

This goes for all Hondas when compared to Acura's. Honda has always recommended regular while Aciura recommends premium. There is a long thread about regular vs premium gas on here. I'll pay for premium because I want the best but to me it's probably a way to make it seem more "luxurious" when compared with Honda.

 

^^yeah what he said. I beleive it is just to make you feel like you are driving something more "premium" by putting in premium fuel. On the other hand, they could have tuned the engine a bit differently with a different torque curve which requires premium (if that is possible or true). on the other other hand (3 hands now?) no one in their right mind buys a honda and wants to put premium in it. Ever. Unless of course is is the honda nsx..that doesn't count though.

But make a note to yourself here. It says premium "recommended" not "required" there is a huge difference here. Personally, I beleive you will get the same power and economy out of using regular. Has this engine made something like 300hp (like the lexus 3.5 v6) then I would have said use premium all day. But it isn't highly tuned and the same engine is making the same power on regular. I personally would go regular,

 

I'm not debating regular vs. premium. I am debating how they are pretty much the same engine, but one says premium and the other says regular.

 

I agree about the idea of making you feel like you are driving something more "premium". I just figured that the Pilot would recommend premium as well, since it's a high compression engine. I don't mind paying more at the pump, but when it's turning into $6 difference now, instead of the $2-$3 it was, I would like to understand why they don't recommend it on the Pilot.

 

You're asking the wrong question. It isn't why the Honda doesn't recommend premium but why Acura doesn't recommend normal.

My suggestion is that you run a few tanks on normal in regular driving to see if YOU can notice a difference.

I'm sure this will start another "you bought an Acura, why cheap out on the gas?" rant to send this thread into the toilet but why pay for something that brings you no benefit?

More important than grade for this car is to buy your gas at a reputable station with high turnover. If that station is a top tier station then so much the better.

By law, all gasolines must have the minimum detergents required to keep the engine clean. Top Tier is a consortium that has set a slightly higher bar for additives - but - remember that all grades have the same type and amounts of additives.

 

Here we go again!!! *sigh*

 

yup exactly my point. It isn't why is honda not asking for premium in honda branded products, it is why is acura asking for it. This was why I said no one ever buys a honda and wants to put premium in it. I meant honda branded products.

 

Curious to know, what do you mean "they are pretty much the same engine"? Based on what? They're both J35s?

You should look up the part numbers for the long blocks on one of the Acura/Honda parts pages. Different compression ratios already tells me they're not pretty much the same.

 

You're correct. For his benefit (since you already know this Taco), the engine is a J35Z2 in the 2015 RDX. The 2015 Pilot uses the J35Z4, which is a variant that is down 21 hp and 1 lb-ft, but generates the torque at a lower RPM.

The 2016 Pilot actually shares the same engine as the 2015/2016 TLX, which is the is the J35Y6, but in the Pilot, it's tuned to regular fuel and generates peak torque slightly higher and peak power slightly lower, and is down 10 hp and 5 lb-ft from the TLX.

pkolanko, you could probably get your RDX timing map modified to be optimized for regular gas if you were so inclined.

 

Yeah, I don't think the RDX and Pilot engines are necessarily a good comparison (at least not the current Pilot - perhaps the old model - not sure).

The RDX engine does compare pretty favorably to the Odyssey and Accord V6 engines however. All of them have a version of the J35 with 10.5 compression ratios.

I'm not sure how accurate this is, but this Wikipedia page (link below) says the 2008-2012 Accord V6 models had the same exact J35Z2 engine as the current model RDX. If the engines are in fact the same, it does beg the question - why does the RDX recommend premium fuel when the Accord does not? I wish we could get a definitive answer on this once and for all. I didn't mind paying for premium when the price difference was $.20/gallon (in previous cars I've had over the years), but a $.60/gallon surcharge does add up.

https://en.wikipedia.org/wiki/Honda_J_engine#J35


EDIT: YoungTL, you posted at the same time I was writing this. I'd be curious to know your thoughts on the J35Z2 and what the differences are between that engine in the current RDX and Accord 2008-2012 if they do in fact use the same engine.

 

YoungTL, are you a member of 780? Just curious

I hate these debates, but alas, I've now been drawn in. Some stuff to consider if you (OP) do plan to run regular instead of premium:

1. Your engine will retard timing and you will lose some power if not running premium.

2. I've heard that running premium keeps an engine cleaner. Is this true? Well I haven't ripped into an engine specifically to check. Premium very well may have more detergents in it. That said, I'd imagine that it would take a number of hers before you'd have a "dirty" engine. Again, can't really confirm this.

3. I would suspect you'd have slightly worse fuel economy. Those who do run regular claim this isn't really the case. Seems hard to believe, to be honest, especially with knowing the additional timing retarding.

Honestly, even if you are paying $0.55/gal more for premium, is it really that much? That's probably like $6-7 per fill up. I fill up once every ten days. I could easily cut out $6-7 worth of crap I likely don't need every week to make up the difference. The other thing is that if you stick to premium, you'll NEVER have to worry about it ever again. No speculations. No wondering. Just peace of mind. That in itself is worth the price difference.

 

Point 2 is incorrect. Higher octane fuels just won't detonate as easily which allows for higher compression and more power. It has nothing to do with amount of detergent or gasoline cleanliness. I used to be under that misconception as well.

 

Haha, I know people that are, but personally I'm not. I've never been much of the tuner type, but I have been to several car meets a number of years ago.

I don't know about detergents, but Shell, in particular, sells 91 octane fuel with 0% ethanol, while 89 and 87 tend to have 5% and 10% ethanol, respectively. That will certainly result in worse fuel economy, although maybe not enough to make a huge difference.


If you redline the engine daily like I do, I wouldn't use anything less than what the manufacturer recommends. Those more extreme forces can contribute to early detonation. And Honda engines beg to be redlined, so I'm not going to stop doing that.

 

I dunno about where you live, but around here the gas stations are always rambling about how premium has more detergents in it. About 10-12 years ago, I had a friend who's uncle was a mechanic and who drove old school cars, like his '67 Galaxy 500. He said he would put premium into it once in a while to keep the injectors and engine clean. Is it true? I dunno. Maybe it is misinformation, but i haven't seen much supporting your theory

Yes, you are right about the higher octane and resistance to early detonation, but I think there's more to it than just that.

 

You sound like my kind of driver. We would have a blast driving lol.

I didn't know about the 0 ethanol in shell premium. I now understand why they are so much more expensive than everywhere else.

Here the only company rambling about detergents is shell v-power stuff, I don't really hear about it from anyone else. I personally don't beleive the hype from shell anyways. So I stand by my understanding till actually proven otherwise. But I could be wrong for the manufacturers that do actually claim they do. I have also heard about older people saying they run premium to clean the car. I think thats where the misconception of cleaner fuel comes from.

 

Ethanol content is regional but think about this:

There is no such thing as mid grade gasoline. Stations have two tanks - premium and normal. The mid range is mixed in the pump.

A station either sells gasoline with ethanol or it sells it without ethanol. Non-ethanol gasoline generally commands a $1 per gallon premium.

You might want to ask about that if a station says their "premium" has no ethanol but their normal does. You might also want to take a photo of a pump that says "91 no ethanol - 87 10% ethanol"

 

Premium does not have any added additives. Shell is a top tier member so it has the same additives as any other top tier - including COSTCO.

Top Tier Gasoline

 

Thanks ceb. So I stand by my point. I hope this helps some people get over the misconception. This, along with people who think putting premium in a car that calls for regular will somehow equal more power, it simply won't,

 

I'm aware how mid-grade gas is made. I don't know why they even offer it though, since nobody recommended it (89 octane) since the early models of some Chrysler Intrepids.

It stands to reason that if you mix a 0 and 10% ethanol solution in equal volume, you'll end up with 5% ethanol by volume. Why would it be impossible for them to fill their regular underground tank with ethanol gasoline and their premium underground tank with non-ethanol gasoline?

And it says 87 octane is "up to" 10% ethanol.

 

I can't speak to the 2016 Pilot, but the 2009 through 2015 did specify regular fuel; however, for maximum towing capacity Honda specified premium fuel. As to running regular in an RDX, never did it with my 2010 due to the Turbo 4, but in my 2014, I will use regular when I believe that the price gap between premium and regular is ridiculously large; however, even at that I try to mix in at least one tank of premium every two weeks.

I know others will say that it makes no difference between the two, but for me it does. The RDX runs smoother and doesn't gear hunt as much at slower speeds under hilly conditions with premium.

 

Actually, the Honda Pilot and Acura MDX are the same exact Engines. I am stating the Honda Pilot is a higher compression ratio than the RDX, but it doesn't call for premium.

Here are the MDX Specs:

Engine Type Direct Injection V-6
Displacement 3.5 liters
Valvetrain 24-valve, SOHC i-VTEC®
Horsepower @ rpm (SAE net) 290 @ 6200
Torque (lb-ft @ rpm) (SAE net) 267 @ 4700
Compression Ratio 11.5:1
Recommended Fuel19 Premium unleaded 91 octane

Here are the Pilot Specs:

Engine Type Direct Injection V-6
Displacement 3.5 liters
Valvetrain 24-valve, SOHC i-VTEC®
Horsepower @ rpm (SAE net) 280 @ 6200
Torque (lb-ft @ rpm) (SAE net) 262 @ 4700
Compression Ratio 11.5:1
Required Fuel Regular unleaded 87 octane

So you can see the MDX with premium gives a 10 HP boost and 5 more torque, but it's the same exact engine.

 

Thanks youngTL. This is the answer I was looking for. I am not debating regular vs. premium. I am debating engine vs. engine fuel requirements. The Pilot seems to have the compression ratio for premium, so why doesn't it even just recommend premium?

 

That is exactly my point to this thread. Not regular vs. premium, but engine vs. engine. 20 cents for an easy decision, because it ended up being less than $3, but now it's in the $7 range, which just has me questioning the need based on the engine itself.

 

These points are valid, but my point in the post is why is none of this happening to the Pilot engine, which has an even higher compression ratio? I was under the assumption a certain compression ratio required higher octane fuel. The pilot is 11.5 and the RDX 10.5, so why shouldn't they both require it. I will gladly pay the extra to run premium, but when you see the Pilot specs stating Regular, you take a step back for a second and question the validity.

 

My question then is... Why doesn't Honda/Acura just state the reasoning behind recommending premium fuel in the RDX like it just stated in the 2009-2015 Pilot?

 

In the US at least, you won't find a pump that offers any ethanol gas alongside a non-ethanol gas.

 

My neighbor was reading this over my shoulder and gave an answer that made me laugh (he's a Toyota guy). He said anyone dumb enough to pay $42k for a Honda is dumb enough to pay an extra 50 cents per gallon for gas. He owns a lexus which recommends premium, but he has only put 87 octane in it since 2012 and has had no issues.

 

In the DC area, the difference per gallon between regular and premium is in the 75 cent range so the difference is about $10.

More importantly, the difference is about 30%. You won't get 30% more gas mileage or 30% more power.

 

BINGO.

I'm doing about 25-27k miles a year. That's about a thousand gallons a year - or $750 - or almost a year's worth of car insurance.

 

Its a recommendation, like asking someone's advice. You know what they say about opinions right? If paying taxes were a recommendation and not a requirement, would you still do it?

 

So what you're saying is, the MDX has 10 more horsepower and 5 more lbs/ft of torque do to running premium gas? Better start putting premium in my 2000 accord.

Somehow we went from RDX vs Pilot to MDX vs Pilot...

 

I don't think it was ever about rdx vs pilot. It was about rdx engine requiring premium where similar powered honda engines do not.

 

It doesn't require premium, it only recommends it.


And to that, I say if you drive the vehicle hard at all like I do, I would highly recommend 91 over 87 for engines that are tuned for it. The J-series that are tuned for 91 WILL EXPERIENCE PREIGNITION in the cylinders at very high RPM.

If you drive like a granny and never make it even into the VTEC changeover point, then I don't see any major issues with running 87.

 

Sorry I meant recommend!

 

It doesn't work that way someone already posted that the engine codes are NOT the same.

You ask us if it's ok to use regular, we suggest you use premium, you've already made up your mind it's ok to use regular, so why start this thread?

People come on here and say they bough an Acura because it's waaaay more sporty than Lexus, yet they then refuse to spend five bucks more at the pump to get the most "sportiness" out of their "sporty" Acura. I don't get it.

The reason the pilot manual says to use premium when towing is due to the heavy load being placed on the engine. It's the same when redlining the engine. In both instances, the engine will retard timing significantly if using regular. Using premium will reduce the amount of timing retard, but it still happens on the J engines. So if you putter around town, regular likely is fine. To get the most out of your 42k purchase, you should use premium. Is it required? No. Is it the better stuff to use, for a few reasons? Yes.

Do as you please, but I'm starting to realize that the true dummies are the ones who purchase the "sporty" vehicle, but then cannot afford to run it the way it was intended. Man, this dead horse is starting to smell really bad from continually being dug out of its grave. Oh well, better keep beating it!

 

How can you mention dead horse without using this emoji?

 

TacoBello....I am sorry I couldn't give you more than 1 "thanks" for your post but had I been able to give you 10, I would have!

 

Our CFO at work has a 2014 Mercedes-Benz C63 AMG (!) and puts 87 octane in it. I DON'T UNDERSTAND!!! He's already had to have it serviced for excess carbon build up (out of his own pocket).

 

What an absolute clown! You don't put regular in an engine like that! I mean damn, how much is this guy making and he still feels putting in regular is ok?