russianDude

I will be using premium gas in 3rd gen RDX. You can use what you like

Madd Dog

And this combo of 2.0/10 speed is also in the Accord, which calls for regular gas and has slightly lower numbers.

I have switched back to premium. It still feels slightly smoother, even though I admit it might be all in my mind. The difference in price with summer gas around here is not too bad. Sinclair premium is $3.13 and Sunoco regular is $2.95, and they are both Top Tier and within a mile of each other.

NooYawkuh

I've gone through a couple tankfuls of 87 since running only 93 for the first 2500 miles. If I've noticed a difference, it's only because I'm conscious of it. If I didn't know what was in the tank, I probably wouldn't be able to tell by driving it.

johnnyhatchback

you have no idea. The state with the most breweries per capita.

corners

$3.13 for premium in NY??

Madd Dog

Yep. At a Sinclair station in the northern suburbs.

Madd Dog

The Sinclair station and the Mobil station are literally a couple of minutes apart. Look at the price delta.

Lend27

I'm curious.
Does using 87 octane have any effect on the Turbo/DI gas/oil contamination issue?
Would 87 octane lead to a higher amount of unburned fuel in the oil vs 91 or 93?

Madd Dog

I think 87 burns easier, as octane is a measure of resistance to ignition, higher octane resists ignition and allows for higher compression.

But I think the basic culprit in gas contamination is the fuel getting past the piston rings in the compression cycle rather than any unburned fuel from the power stroke.

But I am not an engineer, and I could be totally right, mostly wrong, or completely wrong, and any point in between.

zroger73

^ Higher octane gasoline is more resistant to compression ignition (the bad kind that causes ping/knock/detonation) - not to spark ignition (the good kind where the flame front starts at the spark plug at the desired time). Once ignited, lower octane gasoline doesn't burn any "easier" or faster.

Madd Dog

I’ve seen stuff like this in other places. Maybe they were not being precise.

https://www.hemmings.com/blog/2014/0...-priced-fuels/

Yotrek

Yes good article to read, good share..

OliveBread

My anecdote. 90% highway driving.

My wife accidentally put in 89 octane in our SH-AWD RDX from Chevron on the end of very long road trip. The car felt sluggish and it felt similar to driving through mud. Had about 22 MPG.

I ran the tank down to just about 0.5 gallons left. Filled with Shell 92 Octane. Wow, what a difference it made. Had about 28 MPG, and it felt way lighter in terms of pressing the gas pedal, and feeling the responsiveness of the car.

I can't see myself ever running anything other than premium. Even mid-grade felt really bad.

DriverOne

Even if you wanted to attribute a performance improvement to a higher octane, it wouldn't be that drastic. As far as I know, octane also isn't related to mpg performance, but rather things like acceleration. Additionally, the performance difference in modern cars is relatively small: you might notice it if you were an enthusiast and pushing the car to its limits, but not during general driving. That's my understanding, at any rate, but I don't profess to be an expert on that. I also use the recommended premium octane, but it's really just because I'm "babying" the car and following all directions. In other words, it's just me being weird. But it actually wouldn't harm the car to use regular grade gas. As long as people know that, then they can fill up with anything they want.

JB in AZ

As I've mentioned before, I have always used regular 87 octane in my 19 RDX and it performs absolutely fine. Very great acceleration, great fuel economy (my average is right at 27mpg over 7,500 miles). There is a good article discussing regular vs premium in July Car and Driver issue.

I can't speak for poster OliveBread's experience.

This debate will not have a winner. Everyone should use what you feel is appropriate for them.

Dereileak

I wonder if the octane level will have any difference on the carbon build up from being direct injection and the amount of blow by that gets thrown back into the intake

mathnerd88

I've done a couple tanks of premium and a couple tanks of regular and have noticed absolutely no difference.

I've even set my car to sport plus mode to see if there was any difference and haven't noticed anything.

On my previous car, a G37x, I've noticed a big difference between regular and premium gas. The engine would run rough on the regular gas. The engine has a much higher compression ratio than the RDX.

mlody

You guys are lucky. In Chicago area the difference in regular vs premium approaches .80-90c on a gallon. If you are lucky you can find stations where the gap is $.65-.70c however, it is not rare to see an actual $1 difference in the Chicago city.

Now, in our case, we got both cars that require premium and have crappy city MPG. At only .65c difference premium vs regular (Costco pricing) we are already spending over $1000 on average a year using premium gas. Now if the $1 difference spreads out more into suburbs, the cost of driving two cars that require premium it would raise to over $1500 which is ridiculous. Now add that up over a course of 5 years for instance and that really adds up to a significant chunk of money.

When shopping for our next cars, I will definitely factor that and will look for cars that are happy with regular and perhaps only recommend premium, not require.

anoop

^ Interesting. Does Chicago tax the grades differently? Most places the difference is 20-30 cents.

Yotrek

as long as you don't hear knock on the engine when using regular, you're good to go..IMO

mathnerd88

That sounds more like a problem with the quality of gas rather than the actual octane rating itself.

Meto

I just did a 4160 mile trip in 12 days through the mountains and a lot of Highway driving using 87 Octane for the entire trip. Averaged over 24 mpg and had zero decrease in performance compared to Premium..

mlody

As far as I know, the tax is the same regardless of the gasoline grade, but it got jacked up by .19c in the recent days - yey for another hike. Chicago is just being Chicago I guess but the tax hike was state wide.

anoop

I thought the engine automatically retards timing in order to prevent knocking when using a lower grade and this results in some loss in performance.

Yotrek

yes it does, that's why you can use both octane grade..