I was recently at my dealer's and mentioned the cost of gas, etc. and the salesman said that at higher elevations, such as Albuquerque (5,280), that mid-level gasoline is sufficient. He said that if I shop at Costo (premium at $3.79 yesterday) that I could put half a tank of premium and half a tank of regular in. Interesting as I have just been using premium.

Car is only a month old and I have only filled up 4 times but the computer says I'm getting 17.7, all city driving. Not killing me yet!!

 

It is possible to mix both grades to achieve 91 octane which is what your car needs.
17.7 MPG is pretty good for a crossover. My TL gives me about 18 in the city.

 

Mixing regular and premium is lame. If you are thinking about saving few buks on gas (probably even less), perhaps you shouldn't have purchased this car. Gas prices are insane, but difference between premium and regular is still the same, so there is no need to get upset now.

 

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search function. use it.

 

Russian Dude, read my post again. I mentioned using mid range gas and only if that isn't available could a person mix. However, I also stated that the price of gas isn't killing me.

I don't think saving any money is a lame idea, maybe you should try it instead of juding another.

 

For me, this decision would be aided by quantifying the cost savings. If I can save $0.15/gallon by either using a lower grade or blending grades, and I drive 15,000 miles per year and average 15mpg, then my savings is $150/year, or $12.50 per month. Weigh this against the following potential "costs" of using lower-grade gasoline (improbably as some of them may be):

1. Lower realized fuel mileage
2. Reduced engine performance
3. Denial of future warranty claims due to not following manufacturer's recommendations
4. Reduced engine longevity

Definitely not worth the risks for me, despite that fact that I'm typically a pretty cheap SOB. There are almost certainly less-risky ways to reduce your monthly budget by $12.50 (like, drive 60 fewer miles each month).

 

or not beat the snot out of your car and drive conservatively, reduce idling etc...

 

I call on this altitude thing. I'm not a scientist so I don't have hard data to back this up but.......

In my trips through the mountains in Montana, I notice that almost every gas station sells octane booster. Many cars start to run like crap in higher altitudes due to the thin air and the octane boost apparently helps out with that. So how could a car that wants 91 octane in the first place be able to run fine at high altitudes on lower octane fuel?

 

There was a longer thread on this a few month back.
For the life of me I can not figure out why people are still arguing about premium verses a lesser grade in this case MID(89) (10 cents difference).
That is a diffrence of $1.80 per tank. ($3.60 if you would use 87).

When gas was $2.00 a gallon last year you still payed $1.80 to $3.60 more per tank for premium, just like you do currently when a gallon costs $4.00 a gallon.

I just do no see the argument to go with a lesser grade now to save a couple dollars, when you were willing to spend the exact same amount of money when gas $2.00 verse $4.00. Just my

 

I totally agree. I would stick with the required premium gasoline for the turbocharged engine in the RDX.
Like me, I have chosen to use less of the RDX to work, taking the public transport, to address the issue of the rising gas prices.

Using mid-grade gasoline in a high performance turbocharged engine is not recommended at all...

 

I run 89 in my 06 TL and I have no issues... no valve clatter or anything...

 

I would not treat the NA engine on the TL the same as the FI on the RDX.

 

Exactly. The fact that someone would even ask this baffles me.

 

It's because the ECU is detecting you hate your car and is retarding the timing and richening the mixture to compensate. The RDX motor being turboed has less wiggle room to protect the engine and while it probably wouldn't knock under relatively sedate conditions, stepping on the gas going up hill would probably be outside of the ECUs envelope to prevent knock via engine parameters. Just to save a $100 a year, it's a pretty hefty wager against a $35k vehicle.

 

Oh yeah, and how much exactly are you saving? In my area its 20 cents difference between premium and regular, so by mixing two, you will effectively save 10 cents on a gallon. Lets see: @14-15 gallons = $1.40 in savings plus added time to stop at the station to get one half and then another *half*. If you have nothing else to do with your time, go ahead.... When thoughts like that cross your mind, go back and think again why you bought $30K turbo charged car.

 

Obviously, the salesman is not a technical guy at all, a real salesman at his best... making up things that seem reasonable to the common minded...

The engine is specifically designed to run on premium gas for performance and longevity... Turbocharged engines are different beasts altogether, when compared with NA engines.

There are two ways to deal with high cost of gas:
1. trade the RDX for a hybrid
2. use it only sparingly for weekends, and bus the public transport...

If the logic of using mid-grade gas works out, you might as well go all the way and blend premium with 87 octane gas! You might get away with it, with normally aspirated engines, but with turbocharged engines, you risk causing damage to the combustion system.

 

I've used midgrade (89) in my engine for the last 30K. Plenty of power, as good mileage as with 91, and no issues.

Most mid-grade gas actually tests higher than 89. Since I'm happy with the performance and mileage using such, I see no reason to donate an extra 6-7 cents a litre to the oil companies.

 

94 octane always in our rdx, I tried shell vpower once to see if I would see the mpg difference, wasn't that much so I went back to sunoco 94.

Its pricey but I sleep well at night.

 

How about that Racing Fuel From Sunoco, Octane 100 ?

Would it give more power/make the RDX run better?

(For you info I currently drive a Grand Cherokee limited V8, asked my local mechanic and friend If i could pump that just for fun one day, back when gas wasn't so expensive. And he strongly advised me against it... (Race fuel was $7.39 per gallon tonight)

 

No.

 

You would be the guy who's warranty will be voided after they inspect your engine for any type of future engine repairs(if any shall arise).

 

Exactly... Just because you feel the engine is running fine while you are running it on 89 gas, does not mean it's alright for the engine in the long run. Of course, if you plan to keep your car only for 3 years and is leasing it only, then this point for you will be mute.

For those who plan to keep the car past it's warranty period, then proper maintenance of the drivetrain also means running the engine on recommended gasoline grade.

My old 2003 SAAB 9-3 turbo, had the trionic 8 ECU, which was suppose to be "really" sophisticated, and can supposedly handle the use of lower octane gas. Well, after 4 years of the engine on 87 and 89 gas, the engine was running really poorly (and I only used branded gasolines like Shell, Chevron, ESSO). Power was down, fuel mileage was also degraded...

It's like using 94 octane gas in a Formula One race car, tuned to run on 103 octane racing fuel.

If you have to use a car a lot for regular daily driving and gas cost is a really big thing, then the RDX is not for you... It will never be a Civic or an Echo... No matter what gas you use, the fuel consumption will always be way higher than you would like... and saving 6 to 7 cents at the pump each time, and potentially harming your engine... is not worth it...

It's like buying a Ferrari, tuned to run on 91 octane, and then going to the gas station and buying 87 gas...

 

Care to elaborate?

 

This point will be unable to speak?

I would have thought the point would have been irrelevant or moot(pronounced exactly how it looks).

 

To be fair, you have no idea if the above experience was because of the grade of gas you used, some other factor, or that perhaps your car was one of the unfortunate data points on the left side of the bell curve.

Having said the above, I agree fully with this entire paragraph. The reward per unit of risk of using lower grade gas would appear to be VERY low.

 

To listen to you guys, there should be cars with grenading engines all over the place. There must be plenty of stories of people not getting their warranty covered as a result. Can anyone provide me with a few links?

 

You are correct in regards to the SAAB 9-3 engine issues, could be due to anything, but the engine was definitely pinging after using 87 gas in it for a year or so (chevron gas).

But really, all this talk about using 87 or 89 gas in the RDX does not make sense whatsoever... The 6-8 cents you save each time you gas up, does not make the RDX realistically cheaper to run, if you have to drive it everyday.
For me, I have simply chosen to take a realistically cheaper way to get to work, in response to crazily rising gas prices... take the public transport... and use the RDX only on weekends or night outs...
Or the other option one can take is buy a Prius hybrid...

Take a high performance turbocharged or supercharged full gasoline engine and saying it is also super fuel efficient is really an oxymoron. To also want it to save lots of money on gas is also an oxymoron.

It is like saying, "I have a Ferrari F430, and I like it to burn gas like a Toyota Echo... But since it is not an Echo, then I would fill her up with 89 octane gas to save money" But Ferrari recommends 94 octane gas or higher...

If the RDX engine was designed specifically to run on 87 or 89 gas, Honda would say so. Especially in light of the rising gas costs, Honda would be more than glad to "boast" of the RDX ability to run on 87 gas, would it not?

I thnk the best solution is not to try to adjust and modify what gasoline to "feed" the RDX engine to save significant amount of money, but rather adjust how one drives the RDX (less aggressively) and possibly use a cheaper way to get to work and use the RDX more as a weekend or nightly recreational vehicle.

 

I just have to add this in... following up on my previous post above, if one uses the RDX as a recreational vehicle for the weekend or night out, I think 91 octane gas would be rightly used, so that the few times in the week you get to enjoy the RDX, you can have a nice smooth running engine to scoot around.

It does not make sense to put 91 octane gas into a toyota Echo when it runs efficiently and perfectly on 87 gas.

It ALSO does not make sense to put 87 or 89 gas into the RDX turbo designed to run on 91 octane.

For those thinking of using less octane gas to save money, realistically, to really get a significant savings, fill half the tank with 91 octane gas, and the other half with water. You get 50% savings immediately, not the 5% savings, which would not cover the cost if somehow the engine is damaged from long-term use of lower octane gas.

Hypermiling... not modifying the engine needs, is the way to go with trying to lower gas costs...

 

Just before tasking a recent trip, I filled up with mid-grade as the premuim tank at the station was empty. I did not notice a performance difference, but the gas mileage was about 2.5 mpg lower for the part of the trip where I burned that tank (24.6 compared to 27.1). I drove about the same and under similar conditions throughout the trip.

I paid about $0.15 less for the mid-grade than the premium would have cost ($3.66 vs. $3.81). So, for those of you who do math:
The first leg of the trip cost (15 gal × $3.66/gal) ÷ (15 gal × 24.6 mpg) = $54.90/369 miles = $0.149/mile.
The next leg cost (15 gal × $3.81/gal) ÷ (15 gal × 27.1 mpg) = $57.15/406 miles = $0.141/mile.

Bottom line is that it was actually CHEAPER to run premium than mid-grade. While it might not have made sense when regular gas was $1.00 and premium was $1.20, the relative difference now at $4/gallon is insignificant.
BUY PREMIUM.
Of course I'm in an 07 TL-S 6spd, which unfortunately is not turbocharged - so this information does not apply to the RDX.

 

With all due respect, your single experience is hardly sufficient to draw any meaningful conclusion about gas mileage differences between 93 and 89 octane.

- DDB

 

I was on a trip and accidently used mid grade for a tank. Prem was in the middle of the gas pump not on the outside right(as most stations). MPG went down a tiny bit maybe .5 a gallon. Where I noticed the biggest difference was when I step on the gas to pass going uphill on the freeway, seemed to hesitate a little with the power kicking in. That was about it.

As I stated earlier just does not make sense to try and save $1.60 or so

 

Well... Before I got the RDX, I actually considered the RAV4, it was more fuel efficient and does not use premium fuel...

But I did not like the looks and the interior was really boring to me...

Ultimately , for all you folks who bought the RDX, you knew that premium fuel was the required fuel for regular operation... you bought it, and now wanna change it to lower octane which is not recommended at all...

Like I said, given the rising gas prices, car manufacturers are very sensitive to consumers response to this... Acura would not develop the turbocharged engine and recommend premium gas if it did not have to...

Same thing... why not put regular dino oil in the RDX engine, and change it every 5,000 miles? It will definitely be cheaper... but at what cost to the engine?

Adapt your lifestyle to the rising gas prices, or get a hybrid... that makes most sense...

 

I feel the same way about the gas prices now and in the near future. The RDX requires premuim; prices are so high that it doesnt even make sense to pump anything lower than its reccomended requirement of highest octane available by pump. Despite the potential engine degradation or performance losses, it is not worth the extra $3.00 savings, in my opinion. I knew the requirements when purchasing the vehicle, I was expecting averages of 18-22 MPG, and I also recognized that it also required Moble1 Synthetic Oil.

If I was going to be worried that the cost of owning this vehicle would be this "dramatic", as one would explain, i would of purchased a CRV.

 

MAV238 and [RDX], I totally agree with both of your statements above.

 

Are you a statistician?
This is the second time in this thread that you have pronounced someone's experience as inconsequential.
I'm interested as to why my data point is not statistically significant. I track my mileage very closely and have for many years. If there is an outlier, I want to know about it and try to find a cause. In this case everything was the same - before and after - except for the gas used.

 

Well, you do use terms like "about the same" and according to your math, you only filled up 15 gallons, so there was some fuel mixing. How about the real factors at work here...did you have your windows open or the climate control on? What was the outside temperature? What were the roads like? Elevation changes? Etc, etc, etc...

These are why your single set of data points does not make for a concrete conclusion.

 

It means more like "debatable" than "irrelevant". In other words, a moot point is one that can be debated with no obvious and clear outcome from the onset.

 

At the end of the day... it really does not matter how one calculates the fuel consumption... the RDX will average around 18-21 mpg...

Using 89 octane gas is not going to really help in a significant (if any, realistically) way to save money on gas...

Just pump the RIGHT octane gas as recommended/required for the RDX engine...

Then try to save money on gas, by:

1. adopting less aggressive driving habits
2. drive less to work, use instead public transportation or bike
3. maintain proper tire pressure
4. Don't use the "discounted" unknown brand gas from some dingy station on a side road
5. trade it in for a hybrid

Try putting dino oil into the RDX, and drive like snail on a flat road... no impact on engine... well, try flooring the engine consistently... and you will probably toast the turbo bearings in no time...
Why premium gas for the RDX turbo engine??? Why not 89 gas?
Why synthetic oil required for RDX engine??? Why not dino oil?

Just buy something else that uses 89 gas, and also dino oil... remove the stress...

 

I guess I'm used to having people routinely respect my opinions - I'm 2 for 2 in having to defend myself in these forums so far this month.

Its "about" impossible to drive exactly the same and with the same conditions throughout a trip. Being an engineer, I rarely use absolutes.


I also mentioned that I drive a TL, which barely holds 15 gallons. My MID showed about 4 miles left when I refueled. Granted, there was some fuel mixing, but it was on the order of 95% or more new gas.


All factors that I can think of were essentially the same. Windows were up and A/C was on. Temperature was "hot", but I'm sure not the same throughout the trip. This was a there and back trip, so the roads were the same, and elevation changes were negligible.


I never claimed that my data was gospel (i.e. concrete); was just wondering why someone could dismiss it out of hand so easily. In order to draw definitive conculsions you generally need more than one data point. However, it is not unprecedented to draw very correct conclusions based on a single point. It's part of the basis for statistical process control.

Based on the information that I have, I'm convinced that there is a difference on my TL, so I shared the observation. My original gripe was that ddb seemed to have a pattern of discounting people's experience or conclusions in this thread.
Could be that I'm just overly sensitive to criticism and that's just the way it goes here. Could be that ddb has a problem with data points that don't fit in his bell curve. Could be explanation 3.

Anyway, one day I'll figure out how to include pictures in these posts and include control charts... Until then, I'll be vegging out in front of the Celtics game.