TLX recommends premium gas. Looks like it has the same engine that Honda Pilot has (3.5L) which uses regular gas. Does anyone have any details on the differences of these engines?

Carl

 

Nope

 

They share the same compression ratio. After a while, I used only regular and I didn't see any drop in fuel consumption. Possibly 3% in ultimate availalble power at 6500rpm who cares?

 

For all intents and purposes, it's effectively the same motor. Using regular in my 15 MDX would probably result in the Pilot's 280hp rating. Begs the question of whether or not the opposite is true in using premium with the Pilot.

 

Most likely the biggest difference is marketing. Folks might think less of Acura as a luxury brand if it uses regular gas compared to premium. Second biggest reason is Acura/Honda seems to stick to a horsepower hierarchy with the most expensive models always having more HP than the lower priced models with the exact same engine. They do the same for similar sized models from Honda with the same engine where a MDX will have more hp than a Pilot or the TLX I4/V6 will have more HP than an Accord I4/V6. Honda probably uses a more restrictive intake and/or exhaust to drop the power.

 

Could easily be a difference in software, that's how other manufactures do it. Slight change would enable the 91 octane motor to be pushed harder before the ignition retard kicks in. Regardless I would run what's on the gas filler tag especially if I lived in hill or mountain country.

 

Acura is a premium brand and likes premium gas. Honda is a regular brand and likes regular gas. Put regular gas in an Acura, and it becomes a Honda. Put premium gas in a Honda, well, that's like putting caviar in me... I can't appreciate it and it would be totally wasted.

 

It would be interesting to see if they use the same camshafts or if the camshafts are computer driven. Two cars can have the same static compression ratio but different dynamic compression ratios.

An easy example of this is my COBRA aka the ugly kit car. I have multiple ECU programs on my hand held tuner. Street, Street Performance (DD program) Track & Ghost Cam. Ghost cam is the one that really proves the point. The engine is a 5 liter V8 32 valve 4 cam alloy racing engine. Even under the track program its very smooth even at idle. Loud but smooth.

When I run the Ghost Cam - Car Shows, Cars & Coffee etc the engine sound is just like a 65 427 Le Mans engine at idle. What the Ghost Cam does is start the exhaust valve to open early & extends the overall duration to create the ruff muscle era idle sound.

The GC is not all that suitable for DD because it requires more finesse at traffic lights to prevent a lot of tire smoke. Once up on the cams it smooth's out. Car also wants different levels of octane based on the program that is running

 

If you're going to buy an Acura it means you can afford the gas, put what is recommended.

This is the same "argument" that many on the 3G TL forum have.

 

Interesting. Indeed modern computing technology seems to be able to really put different "engines" in cars depending on tune/cam/valve timing using the exact same hardware, as you illustrated.

So in the case of Honda motors which are likely majority recycled up into the Acura cars....if the hardware is the same...then could we say that the Acura arm will have a slightly more aggressive tune/ECU programming to optimally take advantage of 91/93 vs 87 octane?

And with this technology, could it go the other way.? Suppose the same hardware is used between the Honda and Acura cars and assuming the Acura motor is programmed/tuned for 91/93 octane. If we put 87 into the TLX....the modern ECU should be smart enough to obviously prevent pre-ignition. Obviously this works for 1 to 1/2 tank of gas in emergencies...but the real question is would it cause any harm over long time....say years?

 

ONLY if you are desperately in need of that 10HP at 6500rpm.

 

I would follow the recommendations. They are recommended for a reason. It could be very well a marketing scheme to make people think that Acura is upscale. But at the same time, I don't think it is a good marketing scheme as I'd rather tell consumers that regular gas is okay to run without sacrificing mileage, performance, and longevity.

 

there are a number of people spending $250+ for an intake in order to gain about 5hp. Spending the extra $.10/gallon for a whole 10hp would be a no-brainer.

 

Its not just about the 10 horsepower @ 6500. The Torque or twisting force the engine puts on the crank will also be greater at the lower RPM levels. Its about when ping sets in under load. All things being equal the Acura on 91/93 will be able take a given grade in a higher gear than running it on 87. Less shifting = a more comfortable ride. When you do downshift & go to WOT for a pass you will be in the left lane for less time regardless of what speed you started out with.

IMHO $250 will maybe cover a nice meal with wine at a good restaurant. Really not going to worry about using the less than the recommended grade of fuel to save enough to go out to dinner one extra time in a year.



The purple line shows two timing pulls then the timing setting in at a lower advance on my car when the octane level of the fuel was insufficient to support the load being put on the engine. IIRF there was 93 in the tank at the time.
.

 

I used to think that was the case. But I think it might actually be a combo of this, and the actual tune for the engine being the same for both Honda and Acura products. What I mean by that is that I would bet the V6's in the Honda lineup would appreciate premium gas and might even run slightly better on premium. But they are not tuned so aggressively that putting in regular would cause much effect. I would bet that putting in regular to the 2014+ MDX would have no noticeable effect on power but that premium allows the engine to run slightly stronger. Same case with putting in premium to the pilot, you would get a slight bump in power but won't notice it.

Now models like the RLX (310hp) and my MDX/the 4G TL and 3G TL-s with 285-305hp do require premium given the technology to power ratio is not favourable. I.e they are SOHC setups pushing small V8 power numbers and really do need that premium fuel so fully extract that power and you will risk knocking with those and feel a strong power decrease.

Look at the RDX, literally the EXACT same engine as the Accord yet it "needs" premium to make 1hp more? I don't think so. So in that case it is a marketing thing. At the end of the day, OP feel free to use whatever you want, I don't think the TLX needs premium AT ALL, but your mileage may vary (not literally and no pun intended).

 

Not the same reality here as the difference is like 13%, or about +$400C yearly.

This V6 engine has no problem at all handling regular gas, as it does in the Pilot and Ridgeline.

 

$7.69C a week. OK I see now there is a substantial argument for using cheap gas. Just be sure that the cheap gas you buy has the full additive package. Places like COSTCO are a good place to buy fuel, Cheaper than most stations & all grades have the full additive package regardless of grade.

 

The salesman who sold me my 16 TLX told me to use regular gas and was one of his selling points when i told him i owned an 07 TL

 

everyone needs to look at it on a case-by-case scenario.

What may not be economical for one member, may not be the same case for another. What hasn't been mentioned is how much does every member drive on a weekly basis? Some people might be spending $3.00 a week more. Some $10.00.

All I know is I'm likely to spend $8/week on something completely stupid and/or unnecessary. If I can justify that, I can probably justify the $8 on gas

but once again- it's a case by case scenario.

And yes, people DO care about that 10hp more at 6500rpm. Maybe not everyone. But many do. Otherwise you wouldn't have folks asking what intake to get for their car, as one makes 1.5hp more than another.

 

I use only Esso / Exxon as I have another 3c/litre discount.

 

One thing to note - as the OP said - the TLX manual RECOMMENDS premium. I take this to mean exactly what it says - you can put regular gas in if you wish.

That said - I always use top-tier high octane because I like that extra horsepower boost for when I'm carving up the twisties on my way to the grocery store

 

Twisties all the way to the grocery store?

I'm moving to Ohio!!

 

Well - to be fair - in Ohio when we say carving up the twisties what we really mean is dodging giant potholes...

 

Oh, so no different than here

I love over all the cars I see around town with a decal on the back window that says "I'm not drunk. I'm just avoiding potholes!"

 

A similar thread about premium gas exists on the 3G TL forum and I reiterated my same technical curiosity: that Honda appears to re-use much of the same hardware (to what extent, in terms of cams/etc. not as well known) in their Honda cars as the Acura cars. Seemingly the "same" engine used in both marques have two vastly different "recommended" octane ratings....87 for Honda and 91 for Acura.

Looking up the owner's manual exact language for my 06 base TL:


source: http://techinfo.honda.com/rjanisis/p...u/TL0606OM.pdf

And the language is essentially exactly the same for the 2016 TLX from its owner's manual: (except is also adds Acura's endorsement for the Top Tier gas brands)

source: http://techinfo.honda.com/rjanisis/p...BTZ31616OM.pdf

So over 10 years the language is the same and seems that Honda's position can be deduced down to a few points:
Honda recommends but does not require the use of 91 octane.
Using less than 91 octane can cause occasional knocking and reduced performance.
Using less than 81 octane can lead to engine damage.

The question that seems to be a bit ambiguous is....if you use less than 91 octane but equal or greater than 87 octane, will there be long-term issues to the engine? We know it can reduce hp and may cause occasional knocking (maybe in very hot weather) but the owner's manual does not explicitly say it can cause damage to the engine (only if we use less than 87 octane...)

So assume one wants to save that $400 a year (or thereabouts by using regular gas), disregarding their reason for wanting to do so (which is a another discussion) could that be a justifiable savings IF there are no severe long-term engine issues by running 87 octane. Of course the other counter-argument is to not buy a luxury branded car if you cannot afford a few more dollars per week in gas.

 

What about brands like Mitsubishi and Nissan which call for premium in their V6's? Not trying to derail, just that it's not unusual for brands to reqest premium even when they aren't really performance vehicles/needed. For example the mitsubishi V6 makes 230hp from a 3.0l V6 and in contrast the older NA 3.0l BMW V6 made 260hp and required premium.

This is just a really long way of saying things need to be looked at on a case by case basis and not necessarily as black and white as "premium brand needs premium and regular brand needs regular". I drive a 2007 MDX with a 3.7l V6 making 300hp, to me the ratio of engine to power and the request for premium is justified. However in the case of the RDX needing premium to make 280hp and the Accord making 279hp on regular while using the same exact engine is hogwash and I don't care if the RDX is from a premium brand.

 

It's a case by case basis, really. I really do now think that Acura says it, just to differentiate the more "premium" engines. It costs them nothing, is safe to do and all it takes is some slightly different text on some decals, or manuals. There might be the odd engine that might actually require it, but most, at least these days, are ok running one or the other, with the only difference being slightly less HP in the lower octane scenario.

Let's face it, we can argue it all we want, but it's clear people are running regular fuel in their Acuras and we've yet to hear someone come complaining that their engine failed. You know full well- for anyone who's been here awhile- some poor soul would eventually admit to a failed engine due to using regular fuel, and we'd ridicule them relentlessly.

However, we would also dissect it in discussion and pull whatever we can from it and learn from the mistakes. But there's an inherent problem with it all, and that's that no one has come forward with any proof yet, that regular fuel in Acuras is a terrible thing.

 

Agreed 100%. Also Acura is not the first brand to require premium in the same engine in their luxury counterpart. Lexus in 2010 had the familiar 3.5l V6 in their RX and it asked for premium while making 275hp, the same engine in the rav4 and highlander made 269-270 and asked for regular. Interestingly enough, in the 2011 model year Toyota now rated the RX for regular fuel and set the HP the same as the highlander and rav4 further proving it was the same engine and that the only differentiating was one was put into a mainstream brand and the other into a luxury brand.

Something I do wonder about is, does putting in premium into other normal engines also have any net effect? Like for example I am looking at a 2012 Kia sorento with a 3.5l V6 making 276hp, if I started filling it with premium, could I push that to 280-285Hp? I have always been in the school of thought that states that you should only put in the tyoe of fuel the car asks for, but cases like the one presented by Toyota and Acura have ne wondering if maybe all engines benefit slightly from going to premium? I don't know.

 

If the manual recommends it, do it.

 

It won't do anything. If the engine isn't rated for requiring premium fuel, absolutely nothing will happen.

You put a higher octane gasoline in, so that you don't premature ignition of the air/fuel mixture in the cylinder. This is what you would call engine knock.

The only time you would need premium is to resist knock from happening, aka premature ignition of the air/fuel mixture. The best time for igntion to happen is when the piston is at the very top of it's movement, and just about to go down. The mixture explodes, forces the piston down, creating power.

If you use regular fuel in an engine that requires premium, the air/fuel mixture ignites prior to being at top dead center (TDC). Essentially, the piston still wants to move up in the cylinder, but the fuel/air is igniting prior to it doing so and forcing it down prematurely. It's an inefficiency, causing you to "lose" power.

Air/Fuel does not need an ignition source in order to ignite. Simply increasing pressure will cause it to ignite. This is why high compression engines require premium fuel, to ensure the fuel isn't igniting prematurely.

All the higher octane does is helps resist premature ignition of the air/fuel mixture. So if your car requires regular fuel, if you add premium in, you're giving your engine the ability to resist that premature ignition, but there is no reason for premature ignition to happen anyway. The timing will be controlling the ignition itself at that point. The engine is optimized to run on regular. By giving it premium, your lowering the ability of premature ignition happening, but it will never happen, since the spark timing will still be controlling the engine.

I feel like I'm rambling in circles. Does it make sense?

 

So in such a case, the car needs to be designed and programmed to be able to handle the Premium gasoline. The factory ECU can only make accommodations up to a certain extent, when stuff changes. If it's not programmed to handle premium fuel, you won't notice a change.

Back in the day when I had my '03 Accord Coupe, the car stated everywhere that it ran on regular fuel and produced 240hp on regular pump gas. However, there was a rumor that if you put premium into the car, it would actually free up 10-15hp "according to Honda engineers". Well if that is true, the engine is actually running better on premium. However, there is no issue running regular, save for a bit less horsepower.

 

In your post before this one, yes you did make sense lol and yes I do understand what you meant. That is always how I looked at it as well. In regards to what you are saying with your accord coupe is a simpler and much better way of saying what I was trying to say in my previous post comparing the J37 to current engines and how it is case by case.

So now my next question would be, if I could get someone to tune the ECU in the Sorento (for example) to speed up timing I would then require premium to resist pre-ignition and with faster timing right. Does that then increase compression ratio and therefore power? So effectively tuning the engine towards needing premium and actually getting a power increase however much it turns out to be?

By the way thank you for the well thought out replys Adam.

 

I honestly don't know, but I don't think it's that easy.

Compression ratio will not change, based on a change in timing. I know that much. Compression ratio is based on two numbers, actually. The size of the combustion chamber and cylinder when the piston is at the bottom of its run (call it X), compared to the size of the combustion chamber when the piston is at the top of its run (call it y). You compare the two as in x:y. You reduce both numbers in such a manner to get y=1, so you have a X:1 ratio.

compression ratio therefore can be changed by playing with the bore and stroke of an engine. The bore pertains to Cylinder diameter, and stroke is the length of travel the piston covers. If I'm not mistaken, it's proffered to have a short stroke for high revving engines, because the longer it gets, the faster the piston moves-stops-moves-stops, up and down, the more the forces act on the parts and therefore likely the lower the rpm the engine can safely handle.

Anyway, now that we've completely deviated, at the very minimum, you would need an aftermarket tuneable ecu for your car. I have no idea who makes it for Hyundai/Kia cars and who here knows how to even tune it. I feel there is more to it than that though, and I can't imagine it being worth your effort.

 

We ran regular unleaded in my wife's 2009 MDX for most of the summer. She started complaining about how the engine was running in August. I noticed that it felt rough and sluggish.

Switched back to premium and it was back to smooth and responsive. The difference was obvious.

And this was in sedate, relaxed two-unrestrained-dogs-in-the-back kind of driving.

So to those who decree that the only change is a small, unnoticeable loss of power I say "poppycock".

 

You right that CR will not change due to timing changes. Timing just lets you adjust how much spark lead an engine/fuel combo will tolerate. That said the CR does infact change (dynamic CR) when the engine is running but the same mechanical CR when its not running.. Two identical engines with different camshafts can have different dynamic CR's. When the valves open & close & how much overlap the is when both intake/exhaust valves are open at the same time will change the dynamic CR.

 

But this point if view is not correct either. In terms of the MDX, yes 100% it needs premium, it makes 300hp, it needs to have fuel that won't detonate early in order to perform at max power. In 2011 (roughly 5 years after the J37 came out) Ford came out with a 3.7l V6 making 305hp but this engine had the advantage of direct injection, dual variable valve timing, and DOHC. So for the MDX to make that much power back in 2007 given that engine size is really really good.

Now you look at more modern Honda J-series engines. In the RLX it makes 310hp while still being the same size and relative layout of the other J-series. The rest of the J-series 3.5l lineup in various other Honda-Acura products (and more specifically the same exact engines in a Honda/Acura product like the Accord/RDX and Pilot/TLX) make 279-290hp....while in some instances they make the same power. On one hand they require premium in the Acura and regular in the Honda. How does that make any logical sense? I know that you can state they have different ECU profiles...etc. Howver I don't beleive this because they make the same max torque and same max HP at the same RPMs....while they can look drastically different and end at the same end point, I just don't see this being the case honestly.

So as Adam and I were saying earlier, I think it is really car specific.

 

Thanks guys! It is posts like these that make me love forums. I have learned SO much from forums over the past few years and it is awesome. I don't think I would actually go as far as playing with the ECU for the sorento (not worth the pain like Adam mentions) but it is just very interesting to know how these things work. I think the most I would do is take out some of the restriction in the exhaust. Nothing else more because it isn't worth it.

 

Yes, but it wouldn't look as cool to list "premium gas" as a mod in your sig...

 

Bolded part is not broad enough a statement. It needs premium to run well, even at a small fraction of max power. My 2004 TL also runs noticably better on premium, but not to the degree that the MDX does.

I agree that the degree of need is car-specific.

 

I think we are on the same page man!