Like all of you, I've read the previous threads that go on ad nauseum about whether regular gas is okay for the "premium fuel required" RL. I've read all the admonitions of "if they say it, they know what they're talking about" and "if you can't afford 40 cents more a gallon, you can't afford a premium car either."

Clearly, with its high compression and electronic engine controls, the RL will lose significant horsepower on regular. I know, I know.

All I want to know right now is one thing: will a steady diet of regular gas DAMAGE this car's engine?

 

base on my experience, beside the power lost by using regular gas or plus rating, the engine runs louder. that all i could notice

 

Not sure of long-term effects. The engine automatically retards timing when using regular gas in order to protect itself. In the short term, this leads to less power and (in my personal experience with my RL, on one accidental tank of regular) awful gas mileage.

 

^^^ Agree with Bob. Seems the computer will prevent the preignition from occuring, thus, maybe eliminating the typical long term damage you would experience with the piston, rings, valves, plugs, etc.

But if your goal is to save money, you're wasting your time. To prove it to yourself try a test and see how many miles you get on a tank of 87 versus 91. Then compare that difference to the cost difference.

 

Good luck finding 91, I have to do the 93 thing. I just got mine 2 months ago and even though I love my RL, I came off a Lexus es300 that took 87. Making the jump from 87 to 93 is a real eye-opener.

 

^^^

Grades of gasoline octane vary from state to state. The "premium" fuel can range from anywhere from 90 to 93 octane.


I'm sure downgrading to regular/mid grade will not cause horrific consequences, but I tend not to stray away from what Honda/Acura recommends.

 

Octane ratings offered will vary. I think its based on altitude

 

Oregon premium grade is 92 octane. Regular is 87 and plus is 89.

 

The answers to, "Is it smart?" and "Is it damaging?" are pretty much the same:

1. MPG will go down.
2. Performance will drop.
3. Lower octane fuel doesn't burn as clean as higher octane fuel, therefore leaving more deposits.

 

I've heard the same responses when I asked about 100 octane gas. Everything was bad news. So if 89 is bad and 100 is bad, I guess 93 is the silly number.

 

That's hilarious really. When I drove the Lexus I only needed 87 so that's all I focused on, even though I took it all over, I never paid attention to the high grade.

I guess you learn something new every day.

 

Here in Utah, "low" grade is 85, "medium" grade is 87, and "premium" grade is 89. I think these are lower than in most places because of the altitude.

In regards to gas mileage decreasing with lower grades, I'm not so sure. Since I bought my car in March, I've been conducting my own experiment. When I first purchased the car, I used 89 (Utah "premium") for 2 1/2 months and have since been using 85 (Utah "low" grade). I can definitely tell a difference in performance, but because I use my car as a commuter car, it is negligible. As far as gas mileage, below is what I have been getting while tracking MPG so you can draw your own conclusion.



My driving style has been the same for the entire ownership of the car and it has mostly been used for the same route (37 miles to work and 37 from work to home, 5 days a week). Of course more data collected and analyzed would be more conclusive since there are so many other variables, but so far for me, changing gasoline grades hasn't dramatically affected my MPG.

 

I can't believe they sell 85 octane in Utah. I've driven through there twice and both times I almost put it in my car which has a minimum rating of 87.

 

There are also seasonal changes in refinement. We have summer grade fuels and winter grades. (Which is a favorite excuse to jack up fuel prices twice a year....or any excuse, like an ant just farted in Iowa will raise fuel prices 5 cents at the pump from morning to afternoon)

I do notice subtle differences by season, and even by some brands. But nothing that makes me worship one or the other. It is rare to find 89 octane in my area, so I usually use 93.

I have read that burning higher octane than required for the vehicle does nothing additional and it simply burns off. Somewhat like taking extra vitamins, your body metabolizes what it can the rest just makes your pee more colorful.

But I do notice a difference the rare time I used < 89 octane. I suspect most of that was the ignition being retarded and ULEV working to deal with additional emissions.

 

Around here, high test gas is 93 octane, but in Colorado, where I visit twice yearly, it's 89. Either worked fine in my RL.

That's a great graph, jhal! Thanks for posting that objective information. My personal experience with 87 (low test gas here in Ohio) was not good. Maybe the gas was not good?

 

Thanks, Jhal. I agree that's great info.

Question: Did you car run any rougher/louder? Or merely a little slower?

 

I want to add my appreciation to jhal. That is great data sheet. The thing I noticed is that the MID indicated mileage is VERY close to his calculated mileage over time. Some have said in the past the the MID wasn't accurate but his data shows it is very accurate.

 

YES it can damage your car. More specifically, your EVAP system and/or your catalytic converters. On some cars using low-octane fuel will set a fault code and sometimes it means the charcoal canister has taken a crap.

And guess what, because the dealer found out that your knock sensor wasn't faulty, they can probably track it down to low-octane fuel thanks in part to misfires in every cylinder and deny your warranty claim. Ouch. Now your car probably won't pass smog either, if you have it in your state.

Even though you didn't ask.... no, it is not smart to risk spending hundreds (probably a few hundred on the cat alone) on a new cat(s) or charcoal canister in the pursuit of saving one or two bucks each fillup. Roll the dice if you wish. After all, the guys that specified 91/93 octane for your RL are only mechanical engineers, they don't know jack squat about what's best for your car, even though they're the ones who designed the engine..... you have nothing to worry about!

 

^^ Yes, forgot about the possible impact on your catalytic converter. I've read that elsewhere in more detail. I believe Billy Mays is right on that one. He's also right that it amounts to a few bucks on a fillup (if that). That's one less Big Mac and fries a week. Skimp on that instead, and your car and body will be thankful

 

I haven't noticed it running any rougher or louder. The change in acceleration is quite noticeable though. It still has a lot of "get up and go" with the lower grade, but definitely not as much as with premium grade.

 

I always wondered why our gas here (Kansas/Missouri) does not go up to 93 octane. 91 is our premium. I never knew the altitude had something to do with it. Good science lesson

Also: Lol at Billy Mays, love the avatar....(may he rest in piece)

 

Dear Billy Costco,

I do not yet have the pleasure of owning an Acura RL.

I am trying to decide whether to buy one, in the event that I should be fortunate enough to come into the requisite money. One dimension among several in that choice is the cost of operation, specifically as it pertains to the gas-mileage toll of SH-AWD.

As this would be my long-distance daily commuter car, the higher price of premium gas compounds the problem. Since straight-line acceleration is one of the lower priorities in my purchasing decision, the fuel question seemed to be worth asking to this expert group of RL owners.

I do not appreciate your condescending attitude, especially since I opened the thread by clearly stating that I was already 100% aware of the very same comments you still felt compelled to make. But I do appreciate your obvious knowledge and your very useful information. For that, I thank you.

 

Think 11 to 1 Compression ratio has something to do with it.

 

BTW..... Dont run anything less than 91 octane (unless its an emergency) like the manufacturer says. Bottom line.

If THAT means this puts you out of your monthly $$$ (vehicle wise), you might want to buy another type car. Maybe the genesis??

 

that was uncalled for.

If you want a car that eats low grade gas, get a 4 cylinder Accord. If you want a serious car, don't go cheap on what you feed it.

93 Bonneville, 2000 Maxima, 2006 TL, 2009 RL all fed 93. I experimented 87 only with the Bonneville and my mileage and performance went down the drain. End of story.

 

What in the world was "uncalled for" about it? Why should I sit in silence and endure verbal abuse from somebody who had the opportunity to see clearly and explicitly that I had already acknowledged his comment in advance, but decided it was more fun to gutlessly peck out an obnoxious reply to a stranger he'll never have to face than to get his ya-ya's out by kicking his own dog?

As for your own comment, "use premium or get a 4-cylinder Accord," why wouldn't I get an Accord with a V6? I don't know about the current ones, but through 2007 they too were rated for regular gas. The elitist inference that yours is bigger than mine is only exposing how embarrassingly your own self-esteem is tied to your rolling pile of glass, plastic and steel.

And finally, your '93 Bonneville's poor performance on regular is "end of story"? Because GM made a car 16 years ago whose engine electronics couldn't retard the timing enough, I should write off Honda's ability to do likewise 13 years later? Man, send me your email address off-list. With those powers of deductive reasoning, I could make a living selling substandard crap to you.

 

TLynn, if you formed your mind before you wrote this thread...congrats.

No, it won't damage the engine, but it will possibly lead to more maintenance issues past the 60k.

Take a chance if you wish.

 

^^^ I was thinking the same thing 037. Looks like you have all the answers and conclusions already TLynn. You don't need our opinions. We didn't design the engine either so what can we say other than cite experiences or reference other articles.

Some friendly advice; Get some thicker skin if you want to post questions on a board like this. Costco and 037 didn't cross any lines. Seems to me you are actually the one now getting contentious.

 

O37, I objected only to the personal undertone of the comments. The information itself is terrific.

I didn't start this thread with any preconceived conclusions. If I was that confident, I wouldn't have bothered to post. I've merely seen on other boards such as ClubLexus that many -- not all -- modern engines rated for premium are actually perfectly happy on regular. I merely wanted to know whether the RL was one of them.

I think it's safe to say that Billy Mays' points, in particular, have convinced me it's not worth the risk in this case. Thanks.

 

I think we switched my wifes '99 3.5RL to 87 after gas went over $2/gallon. I don't think it has made much of a difference but perhaps it has. I am still on the original exhaust and cat. No unusual engine problems. Mostly suspension parts in past 100k miles. We now have 175k and still runs quite well.

However - I am reading this thread with great interest since we just purchased an '05 RL. We are supposed to pick it up tomorrow night (can't wait). I know premium gas costs quite a bit more - but a quick calculation of 15k miles / year divided by 18 mpg (I hope it averages more than that) = 833.3 gallons of fuel. Multiply 833.3 times 30 cents more per gallon = $250 per year. I think I am gonna make the switch!!! I now have to retrain the wife!

 

his comment about getting a 4cylinder accord vs the 6 is because you said you wanted better gas milage.. thus.. a 4 banger would most definitely get better mileage. had nothing to do whether it took premium or regular. -.-

 

Our cars are totally designed for high octane, the cost savings is nothing for average driving (12,000 miles per year) $150 per year on a $50,000 list car. Do not buy a car like this and use regular. Heck, where do you draw the line, extend oil changes to save $40 per year, dirt cheap garbage tires, don't change the diff or tranny fluid when it calls for , maybe you can save a few bucks. Maybe that air filter can go 40k miles, or plugs 120k or 200k?
Sorry to rant but this just pisses me off.

 

Due to a misunderstanding, my car was fueled with "regular" for my current tank. It was a "yellow light on refueling", so it's all regular in there. I am getting 3mpg less at points on my commute than I do at the same speed (cruise) every day. I'd seen this before when I tried it once on purpose, but had sort of forgotten.

 

Impressive, thanks for sharing the hard data

 

Since the ecu detects knock from the sensors it will just retard timing to safe levels. No physical harm will happen at this point.

What happens when knock sensors fail is a different story.


Higher grades burn cleaner (leave less deposits) and resist preignition.

Honestly I would not depend on the ecu to correct timing when my car has an 11 to 1 compression.

Yeah it will work fine but really! do you want to risk it? Damage might not show up right away and will probably show up when the engine is getting up in miles.

If you plan on keeping the car I would advise against it. If you dont at least advise the next owner so they can be aware of the higher risk of engine failure. Engine knock will wear valve guides, valves, and in more extreme cases brake parts eventually.


Its hard to get more power out of a smaller displacememtn engine so thats when higher compression comes in.

Honestly if you can run regular, but why risk the costly repairs that will be associated with it in the end.

 

what about homemade gas thats lower than regular? would it retard the timing so i can use that instead? need to save a few more pennies.

 

cracking petroleum in the back yard, Rich? I can't believe that's cheaper than retail.

 

I would prefer no knock at all. To sense knock, and retard timing, by definition knock must occur at least once. And again with each fill up, or when something changes (engine temp, outside temp, load, ECU decides enough time has passed) because the ECU is wondering if it can go ahead and return to normal timing.

W

 

If the car manufacturer recomend 91-93 Octane Gas for the car's performance, and You bought the car because luxury and performance and adrenaline rush feeling when you put the feet to the floor........then ... DON"T PUT CHEAP GAS.... If You want to use 86 octane gas....Buy a CIVIC having same performance on both gas.