Request for those that put REGULAR gas in your RDX (gasp!)
 

Hello.

This request is for those of you that put Regular gas in your 2019 RDX. You likely hide your face in shame, or maybe disguise yourself when pumping gas at the gas station :) but you know you skip the Premium and push that button for Regular!

I'm curious to know what kind of terrible things happen to your RDX due to this Regular gasoline. Does it knock? Ping? Is it sluggish? Reduced performance? What have YOU personally experienced from using Regular gas instead of Premium?

If this is you, could you PLEASE take a minute to shoot me a PM and let me know? I'd greatly appreciate it. You could post your reply here publicly, of course, but I understand if you'd prefer to avoid the ridicule. Thanks very much.

Oh, for the rest of you reading this post, please don't say "If you can afford a premium car you should be able to afford premium gas." It's already been said. ;)

I came from an 05 TL where premium was required. Since buying the A-Spec RDX I've been putting in regular gas. I have not noticed any discernible difference in performance.

As the Accord 2.0T makes 252hp on regular gas and is otherwise the same engine (same engine code AIUI) I would assume that running regular means the RDX motor makes 252hp instead of 272hp. The electronics are sophisticated enough that it should be easily able to handle it - Mazda does exactly this with their 2.5T, it's makes 227hp on 87 and 250hp on 93.

The FACTS

1. The only Acura that currently requires premium gasoline is the NSX. It is recommended in all others.

2. In order to achieve the peak advertised horsepower and torque ratings, you must use premium gasoline.

3. The peak horsepower and torque ratings are achieved only at wide-open throttle.

Turbocharged Honda engines use a torque-based engine control system. This means that pressing the accelerator pedal requests a specific amount of torque from the engine. The ECU determines the best way to produce the desired amount of torque in real time using valve lift and timing, ignition timing, fuel flow, throttle blade opening, and turbocharger boost. If pressing the accelerator pedal halfway requests 150 lb-ft of torque, the engine will do what it needs to do to produce this amount of torque whether you're using regular or premium gasoline. Using regular gasoline will simply limits the maximum amount of torque the engine can produce. In short, there won't be any difference in performance in "normal" driving, but the maximum amount of torque will be reduced by a relatively small amount. Very few drivers regularly push their accelerator pedals to the floor.

Because of the adjustments the engine must make to operate on regular instead of premium, fuel economy will decrease a bit which will offset some of the savings of using regular gasoline instead of premium. Also, premium gasoline tends to contain even more detergents than what is required by law or to meet Top Tier standards which can help keep your fuel system cleaner.

The vast majority of RDX drivers won't notice a difference between regular and premium gasoline. In fact, about the only time you may notice is if you take two identical RDX's to the drag strip - one filled with regular gasoline and one filled with premium gasoline. The race will be close, but the one running premium will win.

With that said, when I spend the money for a "premium" vehicle that recommends premium gasoline, I run premium gasoline. I DO use wide-open throttle regularly and want the best possible performance under this condition.

I'm pushing 5000 miles on mine. I did 1500 miles on regular, 1500 on premium and now back to regular where I'm going to stay. There's was no noticeable difference in performance or mileage so I see no point in wasting 60 cents a gallon (30% more at today's prices) for the sole purpose of making my exhaust gases more expensive to produce.

In my area "regular" contains "up to" 10% ethanol (87 octane) or 15% ethanol ( 88 octane ), while "premium" often contains 0% ethanol ( 91 octane ).

Ethanol produces less energy per unit volume than gasoline but the price difference for ethanol-free gas is huge. It was $0.70 but it just went up to $0.80 per gallon in my area, $2.86 vs $2.06. Ouch!

BTW, this also goes the other way with 15% ethanol fuel; the small reduction in per-gallon cost usually doesn't make up for the decreased fuel efficiency.

Our MDXs are noticeably peppier running ethanol-free premium, and get measurably better fuel economy ( but not nearly enough to compensate for the cost difference vs regular at current prices ). They get a steady diet of premium, as does my 2019 RDX, but that may be about to change.

Technically, the ethanol-free premium gas is reserved for "collectible cars, boats, off-road vehicles, etc", but I have yet to be given any trouble about pumping it into my not-so-collectible vehicles.

Recent study done on burning regular vs premium when premium is only recommended. Earlier studies with different vehicles (including an Acura) had the same outcome.

https://newsroom.aaa.com/2017/12/don...s-worth-price/

https://newsroom.aaa.com/wp-content/...heet-FINAL.pdf

https://newsroom.aaa.com/wp-content/...rt-FINAL-2.pdf

"no benefit in using premium gasoline in a vehicle designed to operate on regular fuel"

The RDX will self destruct if you put in regular. It will realize its the same engine and transmission in a Honda that uses regular and die in shame when it realizes its been pretending to be a luxury vehicle this whole time.

Regular *recommended* has made it around the entire lineup now!?!


I'll be sticking with the (A) then!

'cuz recommending premium fuel makes it a luxury vehicle, right?

Of course, you have to use premium fuel to extract the finest grades of leather and soft touch materials or its just a regular car that uses regular fuel. Who would want that? Premium fuel is reserved for premium luxury vehicles. If I don't use premium fuel the Acura RDX is built on a throne of lies!!! loll

Winter is coming, bend the knee!

Thanks to everyone for replying, I really appreciate it. I was taking notice of local gas prices and saw that the spread between Regular and Premium was close to 90 cents in some cases. That's an insane difference. Anyway, thanks again!

Read a few articles and I am no expert or pretend to be....but a few of them stated when a vehicle states "recommended" ur better off sticking with Regular and probably the most important factor is using a quality gas product...Top Tier seems to be 1 that is often recommended. https://toptiergas.com/licensed-brands/ and I tend to goto busy gas stations as the gas should be "fresh" usually goto good old Costco!!

It is likely not worth the extra cost in premium fuel for the amount of MPG/HP gain, as AAA already did a study and another poster factually stated that if you look at Acura owner's manual it only "recommends" and does not "require" premium. The only car that does require premium is the NSX.

The only time where it is a clear detriment to use regular all the time is if there is noticeably ping/knock...as that AAA study demonstrated in that Audi engine.

Obviously others will gladly pay the price difference to extract a bit more mpg/power out of it. Whether that price/performance discrepancy is worth it? Up to each driver to decide

A summary of actual research data:
https://cimg1.ibsrv.net/gimg/acurazi...c328ad388c.png

Note those red statements are only found under "extreme" driving condition. Usual city/hwy driving saw essentially NO benefit between using premium and regular. (Unless the motor knocks on regular, in which case you should always use premium, obviously)

Basing my usage averaging 10 gallons a week.

10 gallons a week x 52 weeks = 520 gallons
520 gallons x $0.60 savings using regular = $374.40 over that year

And u will find people that say..oh its only $374.40......I would be pretty happy to find $374! lol

This is copy and pasted from my cars owner manual; (TL with the 3.7 page 468)

"Your vehicle is designed to operate on premium unleaded gasoline with a pump octane of 91 or higher. If this octane grade is unavailable, regular unleaded gasoline with a pump octane of 87 or higher may be used temporarily. The use of regular unleaded gasoline can cause metallic knocking noises in the engine and will result in decreased engine performance. The long-term use of regular-grade gasoline can lead to engine damage"

FYI, The TL basically required premium.

Yeah seems like a requirement to me for the TL. Unless your okay with potential engine damage.

In the RDX, I use about 30 gallons a week. This adds up quick. Premium here ranges $0.60 - $0.80 more a gallon. It used to be $0.40 more a gallon when I got the RDX nearly three years ago.

We aren't talking about a TL here, the new RDX is only recommending premium, not requiring it like the TL (and most all past Acuras) did

My TL (non S) says that it is designed for 91 octane and using lower may decrease performance and can cause knock. Then says that using lower than 87 octane may cause may damage. In CT regular is $2.23/gal and super (93) is about $1 more. I do about 26k miles per year, so about $1000/year regular vs Super. BTW 91 octane is almost impossible to find around me.

And it soon could be $1 (or more) extra per gallon.

Oh. I hope not...

I haven't tried to put in Regular Fuel; but, to give perspective, I use Premium Fuel (Costco or Chevron) and have spent a total of $908.25 since I purchased in September 2018. Running regular would save me about 10%.

https://cimg6.ibsrv.net/gimg/acurazi...bb6b645940.png

Costco Top Tier premium a couple of miles from my house costs about $0.45 US more than their regular at the present time, so I just go with the premium especially since it is currently $2.26 a gallon. I would not expect that price to be the case long term. Compared to the total cost of ownership of the vehicle, the difference does not seem to warrant low balling the octane even if it does not make a huge difference in performance and longevity.

I know that were talking about the RDX its just people were saying only the NSX requires premium.

is that an app? What is it, looks pretty cool.

Yep, absolutely true. But I wanted to hear from folks that used Regular gas in the RDX they already own, since I don't own one. At the end of the day, that's what this forum is for, right? Happy posting.

https://cimg2.ibsrv.net/gimg/acurazi...92291ca73c.png
this is what it say in the manual.

I've tried all grades from 87 to 94. My observations concur with those of the dog. It does seem like the accelerator has to be pressed further to get the same performance with lower octane fuel. Further, there seems to be odd surging with lower octanes, as though someone was lightly and variably applying the brake while accelerating. Stronger and smoother with 94. That said, my experience has shown :moon:-o-meter measurements are not always accurate. At some point I would like to dragstrip test the various grades to know for sure.

Of course it "CAN" lead to engine damage. But I highly doubt anyone uses LESS THAN 87 octane!

And as already stated, it reads that it "recommends" 91 octane.

We obviously know it can lower performance, as noted in the AAA study the performance can be either miniscule or un-observable.

The fact remains that there is no "require"-ment to use 91 vs 87.

For comparison.

The following is found in the 2019 NSX Owner's Manual and it clearly states a fuel "requirement" for 91 octane, and it recommends a 93 octane:

https://cimg4.ibsrv.net/gimg/acurazi...aecf5e6d8e.png


https://cimg2.ibsrv.net/gimg/acurazi...2385f2d5d0.png

Reading the language between the RDX and the NSX. It is clear that there is a distinction between:

• Fuel octane "requirement" (91 octane for NSX, none for RDX)
• Fuel octane "recommendation (93 octane for NSX and 91 octane for RDX)
• Warning for engine damage (less than 91 octane for NSX, less than 87 octane for RDX)

Honestly, this discussion is not much different from the "change my oil every 3,000 mile" threads. Technology has changed; just some of our habits/prejudices haven't.

If it makes you feel better, run premium. It's not required and the benefits are minimal. It's much more important to run Top Tier gasoline.

Obviously there are owners here who the $150+ per year is irrelevant. There are also those here who will drive across town to save $0.05 per gallon too.

My Audi TT RS requires premium. My Tacoma takes regular. When we finally purchase an RDX sometime later this year - almost pulled the trigger on an MDX just before New Years - we'll run regular. What used to be a $0.10 per gallon differential has grown to way over $0.60 per gallon in my area. For me, and the mileage my wife puts on her car a year, there in no benefit to running premium.