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Why do you need to be convinced to go either direction? If you want to put in 87 then by all means, do so!
Just don't go and preach to everyone to do the same.. Some people follow manufacturer's suggestions, some don't. Why does there need to be a thread to talk about it?
Our 08 Acura TSX has high compression pistons and apparently requires premium gasoline. We've owned the car since new and my guess is that we ran three tanks of premium through it before switching to regular. It runs fine on regular and I could not measure any difference in fuel economy. After running about 5000 gallons of fuel through it I'm glad I didn't waste money on premium fuel.
Why do you need to be convinced to go either direction? If you want to put in 87 then by all means, do so!
Just don't go and preach to everyone to do the same.. Some people follow manufacturer's suggestions, some don't. Why does there need to be a thread to talk about it?
Did I preach to anyone telling them to use regular? Nope....
What I am asking for is a reasonable explanation for the RDX needing 91 while the Accord V6 doesn't. Not unreasonable considering the motors in both are identical.
As to the question about a thread talking about it, this is a car forum. We can talk about whatever we like concerning the RDX, right?
Sure thing doc if you happen to think that somehow, an epiphany will happen and the other hundred threads on here won't have a definitive amswer, yet this one will..
Like dirletron said, it's been discussed ad nauseum but feel free to continue this fruitless quest
So, not to beat the already-dead horse... I grew up in New England and then moved to California, where the fuel choices were 87/91/93 octane at the pump. A few years ago, when I moved to Colorado, I found that the octane grades available here are 85/87/91. Given the differences in octane available (and I'm sure there's probably a reason behind that, like the altitude maybe?), is the 91 recommendation across the board, or is it just a general mid-grade recommendation?
Quote from acquaintance who is an Acura/Honda shop foreman with 20+ years experience: RDX has a completely different ECU module than the Honda Accord V6, with different mapping. Also different valve timing.
Sounds reasonable to me. Again, it is personal choice. I choose to stay with the hi-test. (whatever happened to Chevron Custom Supreme...I loved that white pump stuff and it's higher octane, so did my Harley!)
Also, when I've read those articles in CR, etc. that speak of people wasting money buying premium fuels when they don't have to, I think most of that is people buying vehicles that recommend regular fuel (like a Honda Civic or Toyota Camry) and then put hi-test in thinking it will make a difference, when it doesn't...just my read.
@RockTheGlobe: You are right, altitude is the reason why high plateau areas can use 85 without issue in cars that use regular. We don't have it here in Flagstaff, even at 7000 ft, because almost any way you drive away from Flag, you end up going down..... In those plateau areas, the altitude stays more consistently high.
@RockTheGlobe: You are right, altitude is the reason why high plateau areas can use 85 without issue in cars that use regular. We don't have it here in Flagstaff, even at 7000 ft, because almost any way you drive away from Flag, you end up going down..... In those plateau areas, the altitude stays more consistently high.
Thanks, Doobiewah. I guess my original question is reaffirmed -- does Acura make an across-the-board recommendation for 91 octane no matter where you are, or is it a "mid-grade recommendation that is 91 in almost all places but might vary in some high-altitude locations"?
Thanks, Doobiewah. I guess my original question is reaffirmed -- does Acura make an across-the-board recommendation for 91 octane no matter where you are, or is it a "mid-grade recommendation that is 91 in almost all places but might vary in some high-altitude locations"?
That is a very good question, but still doesn't explain the 91 vs 87 recommendations for RDX and Accord V6. I appreciate Doobiewah asking his friend again. I doubt the "different ECU maps" theory as the motors have exactly the same hp and torque at the same RPM's and also the same compression ratio. I would be willing to bet a power graph of the two motors is identical.
Thanks, Doobiewah. I guess my original question is reaffirmed -- does Acura make an across-the-board recommendation for 91 octane no matter where you are, or is it a "mid-grade recommendation that is 91 in almost all places but might vary in some high-altitude locations"?
If you use it (91) everywhere, you are OK. I accidentally put the 85 in while traveling through New Mexico on a car that recommended 87, and it ran fine through Flagstaff; but, when I got down to sea level in Phoenix, Arizona, the car ran poorly. I just don't bother with 85 anymore for that reason. A friend lives on the high plateau in Colorado and says all he uses in his Honda CRV is the 85 (and saves money on the 85 vs 87) and never has a problem. He did admit that he doesn't take the vehicle down to sea level....
That is a very good question, but still doesn't explain the 91 vs 87 recommendations for RDX and Accord V6. I appreciate Doobiewah asking his friend again. I doubt the "different ECU maps" theory as the motors have exactly the same hp and torque at the same RPM's and also the same compression ratio. I would be willing to bet a power graph of the two motors is identical.
You could be right. My friend did say that they have to empty the tanks of the 'loaner' cars when they come back and can tell that the customer filled the tank back up with regular, instead of premium (he says they get complaints from the next customer they loan it to), for the Acura products that recommend premium. He doesn't seem like a 'party line' kind of guy. They do end up selling the fuel to the crew for cheap. To be honest, I see the quandary; however, after spending $40+k for my wife's car, I'll just go by what they, and he, recommend...and just have her fill up with Shell premium. I like the peace of mind.
You could be right. My friend did say that they have to empty the tanks of the 'loaner' cars when they come back and can tell that the customer filled the tank back up with regular, instead of premium (he says they get complaints from the next customer they loan it to), for the Acura products that recommend premium. He doesn't seem like a 'party line' kind of guy. They do end up selling the fuel to the crew for cheap. To be honest, I see the quandary; however, after spending $40+k for my wife's car, I'll just go by what they, and he, recommend...and just have her fill up with Shell premium. I like the peace of mind.
The dealer empties 87 octane gas from the loaner cars tanks? I find that really hard to believe a customer would complain about the gas in a loaner car. My local dealer, Ed Voyles, told me several times all we needed to use was regular in the RDX. With the RLX I could see it as it has a lot more horsepower out of its 3.5.
Again, I appreciate you checking with him about this.
lol you are not "wasting" money by running regular gasoline in a K24A2 2008 TSX. You will get knocking by running 87 on a CL9 TSX, this has been beatin to death on the TSX forums.
"Fuels with lower octane levels are easier to ignite, and may ignite on itself without a spark from the spark plug (compressed to a certain point, heat from the cylinder walls, etc). This is called pre-ignition, and you'll hear the engine knock or ping. By using premium fuel (higher octane levels), the fuel can be compressed and ignited at the proper time (when the spark plug sparks)."
If you run 87 on a TSX the computer will adjust by reducing performance to limit most of the damage.
The dealer empties 87 octane gas from the loaner cars tanks? I find that really hard to believe a customer would complain about the gas in a loaner car. My local dealer, Ed Voyles, told me several times all we needed to use was regular in the RDX. With the RLX I could see it as it has a lot more horsepower out of its 3.5.
Again, I appreciate you checking with him about this.
I too doubt the dealer was removing 87 from loaner cars. As to "all we needed", the dealer suspected that might be your tipping point towards buying. They'll say anything.
I too doubt the dealer was removing 87 from loaner cars. As to "all we needed", the dealer suspected that might be your tipping point towards buying. They'll say anything.
Actually I never asked. That was brought up by them.
I too doubt the dealer was removing 87 from loaner cars. As to "all we needed", the dealer suspected that might be your tipping point towards buying. They'll say anything.
Well, it wasn't all of the vehicles. They do make loaner driver's sign a form to fill up with premium. Sometimes they come back full and the next customer who gets it complains about performance issues, so they just drain the tanks of those and replace with premium. I doubt it is very many...only a few I would guess; however, I was told it happens occasionally. I wondered about them just putting in octane booster, instead, if they suspected a fill up with regular. I was told they are very much the stickler when it comes to 'premium only' on those vehicles that recommend it....makes me wonder if they become 'certified used' at the end of their life-cycle for the dealer...and they want to keep them within Acura recommendations? Who knows.
Just reporting what I was told. The two times I got a loaner I topped them off with premium before returning to the dealer. I think the discussion is moot as people will do what they want to do and experiences are so all over the place, who knows....
Then I am going to blow the B.S whistle on this one. I do not see why it calls for premium and sadly, I like you, would like to know but don't think we are ever going to get a proper answer. I stick by what I said months ago about it just being to make the RDX seem premium.
Asking has nothing to do with it. They had you sized up - they're very good at it.
You think so eh? I have an M Roadster and have never used anything but premium in it..... I talked about that car quite a bit while I was at the dealer as my salesman was a BMW fan....
I didn't want to disappoint ThoiBoi and dirleton, so....This morning I filled up with 87 octane instead of 91 and I definitely felt a difference over a 100 mile trip today with highway and city driving.......a bit of hesitation a couple times (which makes NO sense at all)...noisier engine under moderate acceleration....and overall less power while driving normally, especially noticeable on the highway.....I also noticed the same things in my old Murano when I switched to regular (it also was supposed to have premium according to Nissan)
All of this controversy about 87 vs 91 Octane for our RDX's is fun but I just completed an unintended fuel test this week. We drove our 2016 RDX tech from Denver to Austin Texas using what gas stations call Premium. Some pumps showed Premium as 90 some as 91 and one at a Texaco showed it as 93 octane. The drive from Denver 5,280 ft down to Austin 700 ft is downhill and easy in good weather. I'd expect somewhat better MPG going down there as opposed to coming back up to the mile high city. I was going by the average MPG that the display shows. After a fill up and our speed was set on cruise at the posted limit 65 to 75 it averaged from 25 to 27 mpg all the was south. I had no choice but to buy local station brands and the MPG slowly got worse after each fill up, down to a low of 24.5. At first I was angry that the 90 octane premium was causing the poor MPG. I was disappointed to say the least since my around town MPG in Denver was always 25-26 all the time and that is with lots of traffic mixed with a little freeway. This trip was 99% freeway. So getting 25 or somewhat less was pissing me off. I do know that winter grade fuel is more volatile and produces less mileage than summer grade but it couldn't be that bad.
But then came the trip home. After leaving Amarillo in north Texas, we got low so I decided to pull into a Loves gas station/food mart for the first time ever. The pump said premium 90 octane. I thought, aw crap another tank full of loser gas. But as soon as we hit the road and were doing 70, the average MPG started to climb. It got up to 29 mpg. At half empty, I found another Loves and their premium was 91 octane. So in went another 7 gallons. From there to Denver was snow, wind and cold so driving safety was number one. Much to my amazement, at 70 to 75 mph, the average was now 30.4 MPG with no change in speed, elevation or conditions.
My only conclusion is it's not the octane rating near as much as the percentage of the evil ethanol load that some stations sell. I've often read that Exxon Mobil puts in more of it. It's lower energy must greatly affect the engine's performance and resulting MPG. Normally I get Costco premium at home because of the price and mostly the top tier detergent rating. Too bad the actual ethanol percentage wasn't posted on the pump, Not the usual "May contain up to 10% ethanol " sticker. I dread the day the idiot Feds force E15 on us. That will be a real performance and MPG killer. Some day I'll find the station in Lakewood Colorado that sells no ethanol Premium and see what it can do.
I think the difference in your mileage is not related to octane, but to the wind factor. I used to drive from Wichita to San Antonio and there was usually a 3 to 4 mpg difference between going north and going south.
12-06-2016, 01:22 PM
if you happen to think that somehow, an epiphany will happen and the other hundred threads on here won't have a definitive amswer, yet this one will..
