To respond to the above two posts....sometimes, you just can't fix stupid.

Modern ECM systems allows drive-able conditions for motors whose owners put in 87....timing will be retarded to prevent detonation and they are losing on power/fuel efficiency.

Only reasonable use of 87 is in emergencies when you need to get gas.

Otherwise....yeah wow great save $200-300 a year in fuel.....why not just buy a cheaper car and save tens of thousands?

 

rich does not equal smart... he's a textbook example of that.

 

The sad thing is, that MB owner likely paid WAY more to get his car fixed up after using 87 octane, then he will ever spend paying for 91 for that car

 

I actually negotiated really well and paid $35 :P

 

The Pilot engine has a higher compression ratio than the RDX. However, the MDX has the same exact specs as the Pilot engine, so I was just using that as a better example since some posters were saying its a diff engine. I'm not saying that the premium gives these performance gains, I am saying the manufacturer may print that the 10 extra hp and 5 more torque is a result of the premium fuel.

 

I only use premium!!! I was just looking at the specs of the Pilot, because it has been getting rave reviews and saw it's compression ratio was higher than the RDX, yet it recommends Regular fuel and was like "wtf?" I will not put regular in my tank. I bought the Acura knowing I will run premium. This is my 3rd Acura and 7th car that has recommended/required premium.

Your second paragraph is helping answer my question though. My question isn't "Should I use premium?" My question is "How can a higher compression ratio engine (Pilot) not at least recommend it?" And if this higher compression ratio engine has no recommendation.. then why does the Acura even have one? You answered this question with your response about not pushing the engine hard and you should be fine.

Unfortunately, the Acura is not a sporty vehicle, lol. It's a high end CRV. I bought it knowing that and I'm ok with it. Thanks for your advice though.

 

AMG is a total different beast than a mass-produced RDX. AMG engine is hand-made.

 

The purpose of this post wasn't to debate about whether I should use premium or regular. I have never used anything but premium. The purpose was to find out why the PILOT doesn't require it even though the compression ratio is higher than the RDX. Is there something besides compression ratio that you look at in order to determine which type of fuel to run? I appreciate the informative posts who tried to answer this question for me.

 

While the guy should be putting in premium, that isn't the reason that he has carbon build up.

 

It is, partially. For some reason everyone here believes that all octane levels have the same amount of detergents. They don't.

The other part is the driver not mashing the go pedal. By keeping the RPM low, carbon deposits begin to develop on top of the pistons.

Performance engines are designed to be thrashed. If that guy is going for a Sunday drive every time he drives, then he's not doing his engine any favors.

 

^^I've read elsewhere on the net that modern engines really don't need to be thrashed to have carbon build up? (ie it was more true for older motors but now not so much...?)

Anyway I don't know enough technical knowledge to comment either way aside to say...if you bought a C63 AMG and drive it like grandma....what a damn waste of a car!

 

When someone buys it 'because it's the best one' and doesn't understand why, that's when stupid shit like that happens. Doesn't matter how the engine was made, it was tuned for premium as a requirement, not a recommendation, and people still fuck it up. It doesn't matter if an engine has 3 million copies of it out there mass produced, if it was tuned for 91, that's what it's best tuned for.

Compression ratio is not the only thing that makes a difference in preignition/detonation. The other BIG factor is timing. At an air to fuel ratio of 12.5-13.0, it's most efficient and powerful. If the flame generated by the spark consumes all of the fuel fast enough, a high compression engine can run lower octane fuel. If the ignition timing is advanced forward, the tuning favours higher octane.


Basically the RDX engine has a different timing than the one in the Pilot, and makes its power peaks at different points in the rev range. The TLX and Pilot use the exact same engine, but timing is set further ahead in the TLX, getting more power/torque at lower range. The TLX torque curve probably looks different from the Pilot's.

 

Actually, they do. From the Top Tier FAQ - full link below:

Is TT only for my premium gasoline? No. TOP TIER fuel marketers use the same detergency treat rate for all octane grades of gasoline sold at their stations.
Also, TOP TIER gasoline can contain ethanol up to a maximum of 10% by volume. In areas where ethanol is not always used for blending, a TOP TIER gasoline that has passed all performance testing is still qualified as the additive supplier would have tested their product on the appropriate fuel.


Top Tier Gasoline


In addition, since we know that midgrade is a blend of regular and premium, it also makes sense that all fuels have the same additives.


The minimal amount of detergents is set by regulation and is independent of fuel type.


Then there is this


Is Cheap Gas Bad for Your Car?


or THE DIFFERENCE BETWEEN GASOLINE BRANDS


The bottom line is that while some brands have more additives, all grades have an equal amount of additives.


FWIW, DI engines tend to have more deposits.

 

Yup!

I wasn't saying it was. I am with you that different grades does not mean cleaner or dirtier fuel.

I am kind of confused with what you are saying. The reason modern engines are having so much carbon issues is because most are now direct injected. Direct injection causes carbon to build up on the back of the valves because the gas is injected directly into the cylinder as opposed to port injection where gas is injected into the intake manifold and sprayed onto the back of the valves (Thus washing off carbon deposits).

Thrashing the engine won't really do anything to carbon build up on a modern engine with direct injection because there is nothing to clean off the valves. Even fuel aditives won't do anything. The only thing you can do is manually have the manifold removed and valves cleaned.

Toyota is getting around this issue by using a combo of both direct and port injection in their modern engines. It is really smart of them actually. Go onto VW forums with the 2.0t and read the nightmares with carbon buildup.

 

RDX - Sorry, that was really meant for TacoBello's first post (above) but it wasn't on the same page so I couldn't multi-quote it easily. I didn't re-read my post and it came out badly.


The problem about fuels, oil changes and deposits is that many of us are still stuck in the past - 3000 mile oil change intervals, premium has more additives and you've got to do an "Italian tune up" to keep an engine clean.


In reality, OCI have gone from 3000 to about 7500 in Honda cars and up to 15,000 in BMW (although you'll be visiting the dealership far more often with a BMW for "unscheduled issues"), to deposits being caused by DI.


Premium gas has a higher octane rating - that is all. The electronics will retard timing to compensate for lower octane IF the engine begins to knock. This results in slightly lower peak power and might lead to slightly worse gas mileage - however - in normal day-to-day driving it is unlikely that you will ever experience engine knock, so the electronics won't retard timing and there will be no loss of power or gas mileage. This would account for the premium required on the Pilot ONLY when towing.


With cars where premium is actually REQUIRED (like the AMG), then the electronics cannot compensate for the lower octane and long term use can result in engine damage but in theory at least, the use of regular gas (in a non DI engine) would actually keep the engine cleaner.

 

No worries bud! We are totally on the same page in regards to everything you said above.

 

Fixed it for you

 

Hahahah not so quick now!

 

Back when, premium gas was called Ethyl. You had regular and you had Ethyl. Ethyl was marketed either as an octane booster or as an anti-knock additive. Once they figured out that the stuff in Ethyl killed you, they changed the formulation and called it premium. To this day premium is just that - anti-knock.

 

New pilots have direct injection, that is why u can run regular gas. The injector sprays fuel directly into the chamber which allows you run a higher compression with out detonating. Our RDX V6 has injector that spray into the air path then goes to into the chamber.

 

Ceb, I dunno what to tell you. Around these parts, both Shell and PetroCanada state in their advertisements that their premium gasoline has more detergents in it and cleans better than their lower octane gasolines.

So maybe all the ads they put up all over their pumps and TV are full of shit. By the end of the day, I still buy premium, not because it keeps my engine supposedly cleaner, but because it's what my owners manual tells me to use.

 

I just realized you are a fellow Albertan! had no idea . Any local car meets you know about in the summer?

Maybe those companies really do put more detergents in their premium gasoline. That is not what we are arguing. We are arguing that a higher octane does not equal cleaner gas that is all. Unless of course the company individually puts in more detergent (Shell says this all the time), but this has nothing to do with octane...you see what I am trying to say?

 

I thought the RDX engine was also direct injected?

 

Some DI engines have worse buildup problems than others, for some reason. I don't know why that is. VW's have been the worst, and the first IS250 to use DI from Lexus as well. Other manufacturers haven't fared quite as bad.


Interestingly, the NSX uses both port and direct injectors.

 

Nope. It's port injection.

 

I don't think my neighbor is worried about saving $200-$300 on his fuel so much as he realizes it's not necessary to use premium. He spends far more money on fuel for his plane than his cars. I think most engines that "recommend premium" (RDX included) will adjust to lower octane in most situations.


As to your comment on fixing stupid.... you may have a point. Perhaps you should try duct tape. Although it won't fix stupid it will probably silence it.

 

I agree, I don't know why some have it much worse than others. Kia and Hyundai have also been having issues with DI carbon buildup. I should open a shop that fixes bent valves because as more and more engines age...hmm.

Smart of Acura! I guess they figured people would be blasting it quite often and they want to avoid the carbon buildup issues.

interesting. I wonder what goes on at honda HQ with deciding what car gets which j series engine. Another cost cutting measure I am sure.

I vaguely remember a witty quote about silence...what was it again?

 

I have tracked all my fuel-ups (2013) since I purchased the car in Fuelly and noted whether it was 93 or 87. I did a few runs with consecutive weeks of 87 and 93 over the same commute route. No real difference so for the last year I pretty much drop in 87 since the price diff to premium here is about $.50.

As a note I have owned turbo performance cars (Twin turbo RX7 and twin turbo S4) and have raced them in road courses and autox so I am aware of what octane can do on a car and know how ECU can compensate for lower octane on the newer cars. If you do that in my old RX7 or S4 you will be picking up pieces of your engine or apex seal bits from the ground .

If the RDX does compensate I don't really notice it. It may never have been optimized to use 93 in the first place since it's cheaper to use the same injector/timing map that the accord has for 87 (car makes same HP and TQ basically on same engine). Personally I don't think it will hurt the car if you use 87 but I also don't think you will gain that much benefit from 93 either (maybe some detergents added to mix, but you can always buy a bottle of the stuff every 6 months and it would be cheaper).

Also since it is just a commuter car for me I don't really floor the car anyway so.. yeah.

PS. There is a whole MPG / Octane thread if you search for it.

 

It wasn't optimized for 93, it was optimized for 91, allegedly. But in the RDX only makes 1 more peak horsepower than the Accord that it was used in, and no more torque. The RDX either has a broader area under the curve (although I can't find a dyno plot for one and an Accord that was of the years that use the same engine), or Acura just gave the RDX a really shitty tune. That wouldn't surprise me at this point. The RDX seems to be Acura's el-cheapo vehicle. Literally every other vehicle in their lineup gets more attention. For example, while it's ugly as sin, the RLX Sport-Hybrid drives really, really well and is fairly fast. The ILX has a sweet 8-speed DCT and comes with more features than the RDX. The MDX has SH-AWD, and the TLX has SH-AWD or the 8DCT, and is also more aggressively tuned. The TLX happens to have only about a 9% drivetrain loss in the 9AT version, according to the dyno that Chan_Mike did on here prior to modding his, in Sept 2014. That gives it about 25 or 26 more HP AND torque to the wheels than the Accord V6, which is a pretty big difference.

 

I wouldn't take those dyno numbers with much faith. You have no idea how high or low that particular dyno reads. What an engine puts out and what a dyno reads are two different values.

 

I agree with this very very much. I had a 2016 ilx loaner with the 8 speed dct and I was pretty impressed. Not impressed because it was a good car, but impressed because it was so much better than I expected. I thought it was going to be acuras shittiest car. It isn't. The new 2G rdx is (imho). The ilx had soft touch over the whole dash and both the front and rear door upper sills were soft touch. The 2G rdx had a 50% hard plasic dash and hard plastic in the rear doors (I beleive)/ parts of the front doors.The ilx's 8 speed dct was really really impressive! The shifts were silky smooth and the fastest I have ever seen, like instant. Imho the ilx is screaming for a turbo or small v6 though.

I don't know why acura is fumbling around with the rdx, compact luxury crossovers are selling like hot cakes...the rdx isn't doing bad, but it could be doing a lot better. They need to give it a more exciting engine, a more modern transmission, and a better awd system. Better quality materials inside OR more features. Pano roof, heated steering wheel, heated rear seats (I think we get that here?), power tilt and telescoping steering wheel, and the option of nicer/more leather options on the top trim. I actually think the current rdx looks pretty good, I know it is soft, but that is ok for the target demographic. Maybe give us an s-trim.

 

Same with me. Maybe have a regular RDX and an RDX Type S with more power, better transmission, steering, suspension, brakes and sporty exterior.


I don't think they need a Type S for the MDX. The market for a 3 row sporty crossover is too small. I think the MDX is sporty enough for its size. We don't want Dads testing the limits of their MDX with their children on board, do we? ;-)

 

You would think a 3-row sports suv is silly....take a look at audi's q7 s-line, mercedes's gl amg, lexus rx f-sport. They are selling like crazy, flying off the lots in the "sport trims". Acura needs a mdx-type-s if they want to be taken seriously. The mushy generic asian design and technology is getting old fast. I feel like all their current cars are aged already.

 

I did not say it is silly. If they are going to build a Type S MDX, it would be awesome but would I buy, no. But the way Honda/Acura is going with their lineup, they are leaning towards giving the majority of their customers and the govt want. They already stopped their sports/sporty lineup, the S2000, NSX, ZDX, 1st gen RDX, etc because they didn't make money out of them. Those who shop a Q7 S line or GL AMG won't even test drive an MDX.


But I think I understand where you're coming from, you want Acura/Honda to start making sports oriented vehicles to compete with the other luxury brands. The sad thing is we know they are capable on doing it but they just won't. They are now content on making money out of their "boring" lineup.

 

Lol when I said you, I meant like "you" as in general you. Like the general public. I guess I can understand why acura is not going into the sport line anymore. The zdx was sort of a failure (though it is actually a really good vehicle), the 1G rdx didn't sell anywhere near the volume of the 2G RDX. There is a niche market for sporty trims in vehicles, but I guess acura wants the bread and butter right now. You are right though. People who buy q7's and gls rarely look at the mdx. I would say that a majority of people who do buy the q7/gls test drive the mdx just so they can say they did and then when they do, they find it to be a step down in quality and features (though still a very good car, by far acuras best vehicle right now).

Exactly! You got me exactly. I know they are capable of making really good sport oriented cars. Right now they are kind of in between, not quite luxurious, not quite sporty.

 

Haha sorry for misunderstanding that.


If I didn't have small kids, I would have considered the ZDX back in 2013. It got good reviews and tech (back then). Or probably S2000. But practicality trumps everything when you have kids. I was searching for a used ZDX around the socal area and they are scarce. There's one that I saw and the dealer lists it for $38k, ridiculous.


Correct. They are in the middle of luxury and sporty. Which I think most of their customers, including me, are looking for.
And the Acura/Honda enthusiasts are only left with the new NSX with a $150k++ price tag. Hopefully, Honda can turn it around after the release of the NSX.