the smallest difference in prices between regular and premium seem to be at costco. They are somewhere 20-40 cents, a lot of times only 30
cents more. Other places seem to gouge premium prices beyond reasonable.

Yeah, we got a lot of places here that charge 80cents more for premium, thats outrageous. I only go to costco, it happens to be on my daily drive path, which is nice

Did not happen in my RDX. But before this I owned a 2015 Q50S. For a few weeks i started using regular gas because I did not think it would effect anything at all. Come to find out, a few weeks late (2-3 weeks) i started hearing this AWFUL knocking noise.

Eventually I started using premium fuel again. And I always will. It really is not worth the risk , just pay the extra few cents

Each vehicle is different of course and on page 9-4 of ur Q50S manual it states the min octane is 91....87 octane can be used but not for long term, so yes it prob was going to knock. ......reminds me of "needing" regular cream in my coffee! Swore I could tell the difference.....well my beloved wife switched it with fat-free cream....told me a week later...didnt even notice!

I guess you didn't read the manual. It says for the Q50s that premium is REQUIRED. 87 may be used but only for emergency only 91 isn't available. For the RDX it says that 87 is required, but premium is recommended. There's a difference here.

Also, the Q50s has higher compression ratio which requires premium gas.

I'm about a 1k miles on 87 Sunoco.. No issues and getting close to 25mpg. I'll try 91 eventually but it would have to be significantly better for me to stay with it.

Just paid $2.47 for 93 octane at costco

If your doctor recommends something, do you listen or just do your own thing?

My doctor is not selling me cars. Honda recommends Regular for this engine/transmission in the Accord. Just because they can publish numbers with 91 in their ‘premium’ brand does not make regular in this car wrong.

I have used both, and the differences are so slight as to be nearly invisible.

Aged old topic, usually at least one per forum.

Reminds me of when synthetic oil first came to market.... hell, people are still debating about that too.

we are not driving a race car people..... if you really need higher octane to feel the performance, you are in the wrong car.

You mean "vet" ?


https://www.petmd.com/sites/default/...ppyvet.lg_.jpg

You can’t compare cars, which are easily replaceable and fixable if something does go wrong, to a human being’s health.

I work in the healthcare field myself and I can tell you that not everything a doctor recommends is necessary. Sometimes they do it to make more money off of you, adding procedures that sometimes does more harm than good. A good doctor will give you all possible choices, telling you benefits and risks for each one, and allow you to make your decision yourself.

It depends heavily on the vehicle. Some do, some don't.

https://www.caranddriver.com/feature...dodge-charger/

.

well, yeah. What else? Doggies are people too, you know.

This thread is now worthless, full of troll comments by aggressively stupid people with no knowledge of octane and modern turbo engines. To not be a troll myself I will unsubscribe from this thread and resist the temptation to read in the future.

I’m using regular 87 octane fuel in my RDX since the manual only states premium fuel is recommended and not required... I’m also leasing the vehicle so I’m not concerned about long term reliability since my lease term is fully within the manufacturer’s warranty.

Does'nt the TL have a anti kock sensor which will automatically advance timing as soon as it hear pinging ?

Knock sensors are used on all* modern engines to retard timing when knock is detected. However, the engines will only advance timing by a limited amount which is why there's more to lose by running regular in a vehicle desired for premium than there is to gain by running premium in a vehicle designed for regular.

*Some engines (like Mazdas') use the spark plugs as ion sensors to detect detonation instead of a piezoelectric knock sensor, but the end result is the same.

Hi All,
The Costco in my area has only 87 and 93 octane gas. the fuel cap mentions 91 recommended so is it okay to go for 93 octane?
Some engines I have dont prefer to go above the mentioned octane rating.
I tried searching but couldnt find if anyone else has answered this question.

Thanks in advance.

@solaris16 There is no harm using a higher octane than you need, other than to your wallet. There’s also no benefit.

Acura benefits from changing your air filter and your oil. But how does Acura benefit if you buy premium gas at Wawa? Just because they recommend something doesn't mean there is a financial incentive for Acura. Sometimes the recommendation is legit.

It allows them to up their image as a premium brand, and to kick up the rated power over the virtually identical Honda Accord powertrain.

Absolutely agree. On another forum I frequent the topic comes up at least twice a year in each sub forum and usually ends in a blood bath between the two sides. My favorite comment, which will always make an appearance, is “if you can’t afford to put premium in this car then you shouldn’t have bought it.”

That was the argument on the BMW board, but that car said ‘required’, so I put premium in it. I also only used BMW parts, except for cabin filters and wiper blades.

Here, the RDX says recommended, and the same 2.0/10 speed that is in the Accord says to use regular. So Regular is OK, but if you want the advertised power number, you likely need the 91 to get it.

I have tried both, and don’t see much of a real world difference in my day to day driving.

As always, YMMV.

No idea how accurate this is, but...I have read that the higher HP may only be recognized at "pedal to the floor" acceleration. Who drives like this?

Basically, yes, there's no reason to pull timing if the car isn't at or near wide open throttle (WOT) since it won't be making anywhere near peak horsepower, which is around 6500RPM. So, if you're not revving your motor anywhere close to that, it's also not making anywhere close to that advertised power, hence the need for 91 Octane to prevent knock is also not needed. Most every day driving at low speed and low RPM, you likely won't feel the difference. It's when you want that extra performance that you'd feel the difference ... ie: WOT or "pedal to the floor".

And I put the pedal to the floor quite often. So, I guess tally one for me for who drives like that, lol. Not all the time, obviously ... less than 1% of my driving is like that, but if I'm feeling antsy and get a nice open stretch in front of me, I'll floor it. Also when you go to pass some buttplug doing 60MPH in the left lane and then they speed up to prevent you from passing ... that's a good time to stab the throttle.

I disagree with some if what you wrote. An engine can knock at any rpm under any throttle position. It is not confined to high-load/ high-rpm conditions. The ECU’s job is to keep the engine operating at its most efficient level possible, at any rpm and load. It accomplishes this by advancing the timing until it hears a knock and then pulls back on the timing just enough to avoid that knock. At all times, the ECU will use slightly more advanced timing on 93-octane than on 87-octane. Because of that, at all times the engine will operate more efficiently on 93-octane than on 87-octane. For a given amount of fuel, the engine will always produce more torque and therefore more HP on 93-octane than on 87-octane. But by how much and does it really matter in real life?

If your goal is to accelerate a certain “casual rate,” does it matter if you need 22% throttle on 87-octane verses only 21% throttle on 93-octane? Or if you need 20 hp to maintain 70 mph, does it matter of you need 15% throttle on 93-octane versus 16% throttle on 87-octane? Obviously no. Your foot will adjust without knowing it. If you lose 1 mpg at 70 mph because you need 16% throttle versus 15% on premium fuel, is that meaningful? Probably not, especially because regular fuel costs much less than premium.

I agree that the only time you will (may) feel the benefit of premium fuel is under WOT throttle. But that doesn’t mean there is no benefit to 93-octane in daily driving. The ECU will use more advanced timing (just below the knock threshold) under all driving conditions, except coasting when no fuel is burned.

As someone else asked, does anyone use 89 mid grade? I tend to by this in all the time it seems to provide better performance and efficiency in our eco boost Fords. And since most gas has ethanol in it I figure that 87 octane stuff started out as really poor base stock.

At today's prices, the use of premium would have to result in a fuel economy improvement greater than 20% to justify the additional cost. For the RDX, this would be more than 4 MPG on average - that's not happening. ;)

With the RDX's torque-based engine management strategy, that happens automatically. Pressing the pedal by x<100% will result in y torque. Pressing the pedal by 100% will result in slightly more torque with premium fuel.

Don't forget: Ignition timing is only one of several control variables that the ECU in modern engines can control in order to produce the desired output with target levels of detonation and efficiency - there's also valve timing, valve lift, boost pressure, injection strategy (timing, quantity, and duration of multiple injection events per stroke), exhaust gas recirculation, EGR cooling (Mazda), and variable piston stroke (Nissan). :)

Agreed. Running premium fuel will never reduce fuel cost. If using fuel that cost 20% more results in an increase in fuel economy of 4%, the total fuel cost still increases by over 15%.

As you stated, a torque-based system contains many variables. But the “automatic nature” of those variables eventually cancels out. What remains is a more efficient engine on premium fuel, for any throttle position and any rpm. The entire curve (map) shifts.

When using less than 100% throttle, the driver automatically compensates for that curve shift (or lack of curve shift) by using slightly more throttle with 87-octane than with 93-octane. In daily driving, it is imperceptible. And when using 100% throttle, the RDX might be .3-seconds/2-mph faster in the quarter mile with premium. Nearly imperceptible in the seat of the pants. For most drivers, a complete non-issue. Splitting hairs. Nothing more than an academic discussion. Admittedly a fun academic discussion, but still only academic.

Again, they don't have to. If pressing the accelerator pedal 20% = 60 lb-ft torque request, for example, the engine management system will do whatever it needs to do to produce 60 lb-ft of torque by controlling multiple variables. If it's more efficient and less damaging to produce that 60 lb-ft by fully opening the throttle blade and fully bypassing the turbocharger, that's what it's going to do. With electronic throttle control, the accelerator pedal no longer has a direct connection to the throttle blade. You can see this by monitoring the accelerator pedal position and its relation to the actual throttle opening - the latter of which will change even without changing the position of the pedal. :)

The torque-based engine management system continuously finds the best combination of fuel mixture, boost, cam phase position, ignition timing, etc. to maximize efficiency at any rpm/load. The result will be a specific amount of torque produced with respect to a specific amount of fuel burned at some given rpm. For your argument to work, it implies the ECU was not operating at it's most efficient mixture, and then changed some of those variables to find the extra power at a given rpm. Why would the engine ever “want” to operate at less than optimum efficiency? It wouldn't.

If at 20% throttle/2,500 rpm, the “optimal mix” of engine variables on 87-octane results in 60 pound-feet of torque, the optimal mix on 93-octane will result in more than 60 pound-feet of torque. There is no way the ECU will find a more efficient blend of those variables on 87-octane than on 93-octane fuel. Whatever the torque-based system can optimize with respect to boost, fuel mixture, cam-phase, ignition, etc. on 87-octane, it can better optimize on 93-octane because it can take advantage of more advanced timing. On premium fuel, the engine will always be more efficient. If the load demands 60 lbs-ft. of torque at 2,500 rpm, and that requires 20% throttle on 87-octane, it will require less throttle on 93-octane, perhaps only 19%, but still less.

Right, but the driver won't notice that because the ECU will modulate the throttle and make other adjustments to produce the requested amount of torque independent of accelerator pedal position. If the driver requests 60 lb-ft of torque by pressing the pedal 20%, the ECU may open the throttle blade 35% on regular and 33% on premium - totally transparent to the driver. The engine still produces the same amount of torque at the same pedal position while making other adjustments that the driver can't notice.

I may be confused on this.It is my understanding the ECU does not modulate the throttle. The driver does and ONLY the driver. That is how we control speed. Yes, our gas pedal input must “go through” the ECU, but the driver still instantaneously controls the amount of throttle opening. Based on a given throttle plate opening and load, the ECU controls all the variables downstream to maximize torque/efficiency. But it does not control the throttle opening. If the driver requests 60 lbs-ft of torque to accelerate at a certain rate, that is all he requests. He does not request 60 lbs-ft AND 20% throttle. To get that 60 lbs-ft of torque, the driver will simply keep pressing down on the gas pedal until he gets (feels) that 60 lbs-ft of torque. That defines the driver's feedback loop. That is how we control speed. It may turn out to be 20% throttle on 87-octane or 19% the throttle on 93-octane. But whatever it is, the driver controls the throttle plate opening. Is that different than what you said?

It most certainly controls the throttle blade independent of accelerator pedal position. Some examples you might be aware of when this happens:

• On the Honda 3.5L with VCM, you'll see the throttle blade open more during during 3-cylinder mode with no change to the accelerator pedal position to compensate for the loss of half the cylinders (it's more efficient to run a 3-cylinder engine at WOT than a 6-cylider engine at half throttle due to pumping losses).
• The relationship between the throttle opening and accelerator pedal position changes with drive modes (i.e., "sport" and "ECON").
• On some Honda models (the 2016 CR-V I owned and the 2021 Ridgeline I currently own, for example), the throttle opening will increase on its own while the vehicle is going up hill without the driver pressing the accelerator pedal more which gives the vehicle a more powerful feel.

All of these are easy to observe if you use a scan tool with a data logging function and review the accelerator pedal position sensors and throttle position sensors - you'll see they're not always "directly" connected.

Simply put, the driver controls torque, not throttle opening.

Completely agree. My major point was that SOTP, the main difference you're going to feel is going to be at WOT. And timing may be retarded at lower RPMs as well, but nowhere close to any degree as in higher RPM WOT scenarios. This is a pretty good presentation of how much power difference you can be making with different octanes on the same engine. Obviously, not the same as ours, but its a representation rather than anything else. Also, peak numbers aren't everything, look at how much more power under the curve you get at higher RPM.


https://cimg1.ibsrv.net/gimg/acurazi...83ba2bd7dc.png


Here on LI, there aren't many stations that sell 91. So, I normally fill it with 93, and if I remember if my last fill-up was 93 and I'm above a half tank, I'll use 89 to "dilute" it to 91 Octane. There's no point in the extra octane rating since it isn't tuned for it, so it's wasted money. It's also easier on the wallet, seeing as when I do see 91, it's usually only 4c or so cheaper, whereas 89 may be 20c or more cheaper.

And just an FYI, midgrades are almost always made by mixing 93 and 87. Most stations only have two tanks (three for diesel) and they're simply mixed when dispensed. A lot of people don't know this. This has been a "now you know" moment. I have heard of stations having separate tanks for each grade, but I haven't seen any myself.

Are we discussing the same thing? Without question, when VCM engages under light load on the V6, the ECU forces a wider throttle plate opening to reduce pumping losses on the intake side. But once in VCM mode, doesn’t the driver once again directly control the throttle opening? And when the engine switches back to all six cylinders, doesn’t the driver also directly control the throttle opening? The ECU controls the changeover, but once in that new “mode” the driver controls the throttle opening and torque.

And yes, different modes will use a different throttle map. But once in a mode, the relationship between throttle position and throttle opening does not change. That throttle map remains consistent and thereby still gives 100% throttle control and to the driver.

And if you are going up a hill and the throttle opens more by itself, are you in cruise control? If yes to cruise, the driver willing gives the ECU control to change throttle position as required to maintain an even speed. If not in cruise control, I’ve never heard of any car that can detect when it’s going up a hill and “corrects” for the driver not maintaining an even speed.

"Simply put, the driver controls torque, not throttle opening." With respect to this statement, I still maintain the driver does control torque by controlling the throttle opening. The parameters of the throttle map may vary from mode to mode, but once in a mode, the driver controls the throttle opening to arrive at the desired torque.

That’s quite a significant change above 4,500 rpm when the engine can maintain more advanced timing/higher boost and still not knock. And yes, big difference between high-rpm (WOT) and low-rpm.