Hi all,

I am not trying to start another which gas to use, but I am curious if you all are using regular vs. premium in your RDX's? I just filled up for the first time with premium, but I'm wondering if I can get similar performance from regular gasoline. Will this cause knocking?

Thanks much!

 

I have used Mobil Super (93 octane) gas in my fill-ups on my 2018 RDX about 95% of the time. Never tried using anything less.

 

Search bottom is your best friend, plenty of threads about this....

https://acurazine.com/forums/third-generation-rdx-2019-454/request-those-put-regular-gas-your-rdx-gasp-976228/

https://acurazine.com/forums/third-g...ar-gas-986078/

https://acurazine.com/forums/third-g...pe-gas-976269/

https://acurazine.com/forums/third-generation-rdx-2019-454/premium-regular-unleaded-979323/

There are more, just didn't get to them all

 

91 Recommended.

 

Minimum 87 required. In 30,000+ miles I have never used 91. No ping, no knock, plenty of power... 0-60? I don't really care! LOL

 

As JB said, right on the inside of the gas tank it tells you 87 is minimum. I have tried both 89 and 91.

After trying both, i consistently use 91. No, Not because I am afraid of engine knocking - but because the performance difference is palpable. I decided there is no point to buy an almost 50k car and then drive with less acceleration available than I could have. with 91 the car is eager to accelerate and is amazing in sports mode.

So likely wont get you in trouble to use less octane than 91, but car will be more anemic.

 

Decide for yourself. I do feel the difference between 87 and 91+, the car feels a bit more responsive, and medium to hard accelararion seems to come more with ease.
We can focus on "minimum required", but we can also notice focus it says on tank "91 recommended"

 

Thanks, all! I am using Shell 93 VPower. The vehicle is very responsive, and runs well on it, so I will stick with it.

 

I’m pretty sure Honda’s ignition map is based on 96-octane fuel. That means if you use any fuel with an octane lower than 96, the engine will knock. But that’s when the knock sensors do their job and tell the ECU to pull timing/reduce boost until the engine no longer knocks. Amazingly, the ECU can pull timing/reduce boost enough to prevent knock even on 87-octane fuel. Even the Civic Type R can safely run on 87-octane.

It’s not that the engine advances timing on 91 or 93 octane fuel. It’s more that it does not pull it as much on 91 as compared to 87. If you ran 97+ octane, the ECU would not use a more aggressive ignition map than on 96-octane. The ignition map operates on its most aggressive setting on 96-octane. With any fuel less than 96-octane, the ECU is always is a state of pulling timing to some degree.

It is a given the engine will produce less power and get lower fuel economy on 87-octane compared to premium fuel. The engine could produce 10-15 fewer HP on 87-octane than on 93-octane. But can you feel that difference in power? How often do you fully floor your car? And from a financial perspective, the extra .5 mpg you might get on 93-octane will NOT offset the higher cost of premium of fuel. 87-octane will work perfectly and in no way damage the engine.

 

What I do is this: when my driving is all just around town, I fill up with 87. On long trips, I use premium, which is 93 around here.

Either way, I only use Top Tier. I have a Shell Fuel rewards card that gets me 5¢ off each gallon, and the Shell credit card which usually gets me both the cash price, and another 5¢ off a gallon. The Shell stations are plentiful where I live.

 

That's a good idea! Perhaps I will give that a try!

 

Interesting. I’ve always done the opposite. Around town when I accelerate regularly and can appreciate the extra power, I select 93-octane for improved acceleration and to not restrict the engine. But on long highway trips that imply a constant, light load on the engine, like the need to produce at most 25 HP, I switch to 87-octane because the extra power premium fuel permits makes very little difference. Under very light load (highway driving), the difference in fuel economy between regular and premium fuel is perhaps .2 to .3 mpg. Why spend 20% more on premium fuel just to increase fuel economy by 1% when highway trips don’t take advantage of the extra power? I could be wrong, but that’s my perspective.

 

In local traffic, I generally drive sedately. But on highways, with trucks and lane hogs, I find I need acceleration.

Everyone drives differently.

Oh, and I’m retired. So I virtually never need to make time on a daily basis.

 

I have Shell card with Fuel rewards too. I get 15 cents off every refill. The deal is even sweeter if you have T-Mobile. T-Mobile Tuesday get you another 10 cents. I get 25 cents off at every refill.

 

Good info on T-mobile.

Sounds like it should work for Exxon-Mobil, not Shell, but there it is.

 

Wait. The inside of the gas tank says "minimum 87" but the owners manual says "minimum 91."

I use 92 here in the Pac NW and pay $3.86 gallon. Oh well.

 

When 87 was about $2.00 /gal., I filled up with 93 @ about $2.50.

Lately, I've been filling up with 87 @ about $2.80. If I notice a difference, it's barely perceptible.

 

I cant believe on price differences between 87 and 93 on some stations, 60-90 cents!! Costco been very steady with 20-30 difference, on few occasions it was 10 cent more.
Maybe if you drive like grandma, you wont notice, I definitely notice that car runs better

 

91 is recommended, 87 is required.

 

It's even stupider than that. Around here, there is only 87, 89 and 93; no 91, as Acura recommends. 89 is about 60 cents more than 87 and 93 is only about 12 cents more than that. Why would I use 89? Why would anybody?

 

You can usually get 91 at Sunoco.

 

sunoco is the most overpriced station in my area, it rarely has any cars, and I see them going out if business. I like stations that maintain their equipment, sell a lot of gas, and have too tier gas.

 

I use Gas Buddy, and am always surprised to see the price difference between stations that are a short distance away from each other.

 

On another blog, a guy there mixes 93 and 89 to get to his 91.

He’s an engineer, so that kind of explains it.

 

I always wondered if that actually works. I'm an engineer too but electrical, not chemical. Mixing is not blending.

But the difference in price (10 - 15 cents) between 89 and 93 doesn't justify it.

 

I've always used premium...91 or thereabouts...in both our RDXs. Like Madd Dog, we're retired so don't usually need to hurry and we don't drive a lot anyway...we've averaged a little over 300 mi a month since we bought the 2021...so the price difference isn't all that much over time. I do like the acceleration now and then, and zooming on the freeway on-ramps is cool with the AWD now and then. And, the 65 mph speed limits on the local freeways seem to be mostly advisory...doing under 80 can get you dirty looks and occasional one-finger salutes...so it's nice to be able stomp it once in a while and watch the boost 'gauge' light up.

 

Costco Top Tier Premium is what I go with when I can. Not doing high mileage daily commutes make the incremental cost of premium over regular small compared to the total cost of ownership of the vehicle. If I was a high mileage driver, I might look at this differently.

 

Everyone has different ideas about which level gas to use. The only ones who are wrong are the ones who use less than 87 octane...Is that even possible?

Acura advertises the RDX as having 272 hp. What they don't say is to get the HP you need to use 91+ octane. Using lower octane will result in slightly lower HP...like in the Accord with basically the same 2.0T engine.

I am not sure, but I seriously doubt any of us can tell the difference in acceleration between using a WHOLE tank of one vs the other with out instruments...and NO, seat of the pants is not an instrument.

 

What convinces me is that this same engine and transmission is in the Honda Accord, and it uses regular.

So the Accords power numbers are on regular, while the RDX is on premium. Accord is 252HP at 6500 and 273 at 1500 torque. The RDX is 272HP at 6500 and 280 torque at 1600.

So premium holds higher torque at peak, and likely (I don’t want to bother to do the math) holds it proportionally higher throughout the range.

As a reminder, Horsepower = Torque x RPM / 5,252.

 

yes, but ECU programming is different.
Its optimized for 91, and while timing will adjust to protect engine when you run 87, the programming was done assuming 91

 

Yes, but if you never go WOT, I just don’t see much of a difference on the road.

 

I can tell the difference at 1/2-2/3 of WOT

 

I couldn’t, and I went back and forth with this for quite a while.

 

I have been using premium (91 or greater) although I was told I can use unleaded.

 

I mean I use premium vs regular. I’m new so not sure how to edit the original reply.?

 

You only get a certain amount of time to edit a post.

If you are still within that window, an edit button shows, if not, not.


On the Regular vs Premium question, Regular won’t hurt the car, so run a few tankfuls of one, then a few of the other, and choose.

 

Yes. That's because you may be at 80% of max boost at 1/2 to 2/3 throttle. That's a pretty heavy load on the engine.

 

The higher octane fuel slows down the burning rate of the gasoline at higher temperatures and pressures. Under "normal" (sedate) driving you vehicle has little if anything to gain from higher octane fuel. If you are under a hard pull, high load, WOT, your engine could see some benefit from the higher octane.

"For most vehicles, higher octane fuel may improve performance and gas mileage and reduce carbon dioxide (CO2) emissions by a few percent during severe duty operation, such as towing a trailer or carrying heavy loads, especially in hot weather. However, under normal driving conditions, you may get little to no benefit." (From "Oak Ridge National Laboratory for the U.S. Department of Energy and the U.S. Environmental Protection Agency.)

To (slightly) raise the HP rating of the 2.0 Honda engine the engineers can just add some boost and advance the timing a bit. This will likely only help under a heavy load. For normal driving the control module just backs off the time and boost and keep the combustion pressures down thus being able to run fine on the lower 87 octane fuel. Good knock sensors really help. Some years back I did my own study on fuel performance in a vehicle with a higher compression engine. I drove the same interstate route back and forth to work every day. I did logs of fuel usage and mileage over a 30 day period to make the data more accurate. My results pretty much match up with what the government agencies have concluded. I did get an increase in fuel economy but the increase did not keep up with the price of the gasoline. I got something like a 3% increase in MPG but at a cost factor of about 20+%. In other words....I had a net loss in "efficiency when one factors in all aspects of the costs.

Its your dime. If you feel OK to basically pay more to drive your vehicle that is your choice. But the science is clear, the higher priced fuel is no bargain and it will cost you more to drive.

 

thanks for advice, but to some of us extra performance is worth the dime.

 

For the record, high octane fuel does not burn slower or faster than low octane fuel. It depends on the exact fuel. There are different ways fuel can reach a certain level of resistance to detonation.

In the old days, cheap premium fuel achieved that higher octane level by adding cheap additives. Those cheap additives did combust slower. But 100-octane race fuel (pump Sunoco 100) combusts much faster than 87-93 octane fuel. That is what permits high rpm race engines to have most of the gasoline combust before the piston passes 18° ATDC in the power stroke. (At 6,000 rpm it takes 1/1000th of a second for the piston to travel from 18° BTDC to 18°ATDC.) That is also why the fuel costs $7 per gallon.

Most top tier fuel todays must use a high-quality additive package. That is why they cost more. Top tier premium fuels should combust as fast if not faster than their low octane fuels while still resisting detonation at the required level for that octane.