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Discussion Starter #1
10 Automotive Myths
By AOL Autos Writer Eric Peters

Old wives tales and "old mechanic's tales" have a lot in common -- they're often better as entertainment than guides to action.

MYTH #1: Your car will run better with premium gas.
FACT: An engine runs best using the fuel it was designed to burn. Premium, or high octane fuel, is only of benefit if your car's engine was designed specifically to take advantage of the the different burning rate of higher octane fuel. In a car not designed to use premium fuel, it may actually decrease performance and fuel efficiency. Use the type of gas recommended by the manufactuer.

MYTH #2: A smaller engine is always more efficient.
FACT: Depending on the vehicle and how you drive, a small engine may get worse real-world fuel mileage because the smaller engine has to work harder. Example: With compact pick-ups, you can choose either a standard 4-cylinder engine or a V-6. The 4-cylinder may have just enough power to get the truck going, but loaded up -- or if quick acceleration is demanded -- the overtaxed 4-cylinder will be less efficient. Also, wear and tear on the 4-cylinder will be higher -- so maintenance and repair costs down the road could be higher, too.

MYTH #3: You'll make your brakes last longer by downshifting the transmission to slow the car down.
FACT: All you'll do is make your clutch wear faster -- and a clutch job costs a lot more than a brake job.

MYTH #4: It's ok to follow the maximum recommended oil change service interval advertised by the manufacturer of your car.
FACT: Read the fine print. The higher mileage/time intervals (often as long as 10,000 miles on same late model cars) assume "normal" driving -- which does not include the stop-and-go city/suburban driving that most drivers experience. Such diving is considered "severe" in most cases, and dramatically shortens the recommended oil change interval.

MYTH #5: Store-bought oil additives are good ways to increase engine life.
FACT: Using name-brand oil of the correct type and viscosity (see your owner's manual) along with regular service is the best guarantee of long engine life. Good quality oil already has the necessary additive packages to keep the internal parts of the engine free of build-up and so forth; pouring a can of "motor honey" into the crankcase is little better than tossing dollar bills out the window.

MYTH #6: It's more economical to replace an older car with a brand-new one.
FACT: While the new car may be nicer, few old cars cost as much to keep going as it does to keep up with the payments, insurance and taxes on a new vehicle. Ultimately, it comes down to the choice between a predictable monthly expense (the car payment) or the unanticipated expense of having to get something fixed on an older car. But you might go months without having to spend a cent for anything other than gasoline.

MYTH #7: Turning off the air conditioning at highway speeds will reduce fuel consumption.
FACT: The increased wind resistance will actually cause your engine to burn even more fuel than it would with the air conditioning on.

MYTH #8: Cars equipped with anti-lock brakes don't skid so you don't need to slow down when it snows.
FACT: While ABS will help keep your car under control on slippery surfaces, stopping distances increase as traction decreases. Snow, ice and even rain decrease the available traction or "grip" you've got, and you must lower your speed to compensate for the increased stopping distances -- ABS or not.

MYTH #9: Diesel cars are more economical than gasoline cars.
FACT: Only if you drive the diesel long enough to make up for the typically higher purchase cost of the diesel engine. While diesel engines are capable of excellent fuel economy -- and often last hundreds of thousands of miles -- they also cost significantly more to buy. The price difference between a diesel and a gasoline-powered version of the same basic vehicle can be $2,000 or more. It will take many years of driving to make up for that -- and unless you keep the diesel-fueled vehicle long enough -- usually well beyond five years -- you end up losing money overall.

MYTH #10: Large SUVS are safer than passenger cars.
FACT: SUVs, if driven inappropriately, are more likely to roll over or be involved in an accident than passenger sedans. And SUVs often lack the latest safety features -- such as side and head airbags, and stability control -- that are available on passenger cars. The safest vehicles are those that can avoid being involved in an accident in the first place -- and which offer the best occupant protection if an accident does occur.
 

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MYTH #7: Turning off the air conditioning at highway speeds will reduce fuel consumption.
Actually, that's not a myth, it's a fact. I think the writer meant that you lose economy if you turn off the A/C then open a window at highway speeds - which you would due to the increased aerodynamic drag.
 

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Hi Paul123:

___In your fact #1, you still fail to give the reasons for the Pilot using Regular unleaded yet achieving almost identical HP and Torque ratings. I would say the article you quoted is passing along more myth than fact in the case of the X.

___For a more comprehensive discussion of the Premium vs. Regular unleaded, I went to the Magazine called Hemmings – Rods and Performance. In the February March 2002 issue, they had an excellent article on Fuel FactsHot Rodder’s Gasoline Digest. It starts on page 24 if you happen to have a copy.
___So … How much octane do you need? Only enough to keep the engine out of detonation. More than that offers no performance advantage. How do you determine the engine’s detonation threshold? By testing and the first test instrument is your ear. If you hear detonation at wide open throttle, you have a problem. If there’s no engine-related trouble (ie: too much spark advance, lean mixture, etc.) you need a higher octane gasoline.

___Plug reading can also identify a detonation problem. If you see a tiny flecks of aluminum on the plugs, that’s evidence of detonation. Severe detonation may melt the electrodes and/or crack the center insulator.

___Cars with engine computers having feedback control of spark advance will be equipped with a knock sensor (KS). If the KS “hears” detonation, a fraction of a second later, the computer’s software retards the spark advance enough to stop the detonation. All OBD2 vehicles and those pre-OBD2 vehicles offering access to the engines computers serial data stream for diagnostic purposes may allow those using a “scan tester” to view the KS signal. If you can read the KS on a road test, you see detonation with the tester and know there’s no engine-related trouble causing it; then you need higher octane fuel.

___Some late model performance cars having engines with knock sensors, when run hard on hot days, will regularly show KS output and spark retard by the computer. This is because the manufacturer calibrates engine controls for aggressive spark advance to get the best performance in cool weather, then allows them to “save” the engine with KS-driven spark retard during high-load/hot-weather operation. In hot weather, more octane will help engines like this.
___The article was written by Hib Halverson. The reviewed was an individual by the name of Tim Wusz, Performance Products Engineer at Tosco Corporations 76 Performance Products Division. Wusz has worked for Unocal and Union Oil Company, since 1965 spending much of that time developing racing gasoline’s. This article has quite a few more pieces of information in regards to fuel blending, additives from the refiners and manufactures of performance products (lots of myth’s here), history, and definitions.

___From my reads of this forum, the Honda/Acura OBD-II engines may not have KS’s? The only ways to tell if a Honda/Acura owner is using an underrated octane gasoline is by the auditory knock or watching the timing advance at various RPM’s and loads. The Dynamometer has been touted as the best choice but no one here is going to place their X on one to find out. I have never read of anyone in this forum using Regular unleaded in their X’s ever having heard this to date so I would be very careful as to stating facts or myths without the empirical data in place to back up the claims. I have proposed multiple times in the past to look at spark advance at various RPM’s with the two fuels at similar ambient temperatures. If the spark advance is the same, I can pretty much say that the 91 Octane recommendations is only for high temps/high loads as the Honda Pilot brochure suggests only when towing heavy loads as well. Anything else has to be proven by more than some AOL auto writer’s fact myth list …

___To add to the myth/fact list: Will high-altitude gasoline damage an engine requiring a higher octane? Not if you stay in the high country or, if you drop below 4000 feet, you don’t run the engine hard until the high altitude gas is used or diluted with “sea level” gas. I added this one as a possible misnomer to the Octane discussion I quoted above.

___As for the rest of the Facts/Myth’s, either they are well known or they don’t apply to many in this forum in particular. And what is up with the title of this thread? Is it a Premium vs. Regular Gas myth/fact discussion or is it a general Automobile myth/fact list?

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 

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OK, I've read the above, and there sure is a lot of information there. But, I am having trouble assimilating this as it pertains to the MDX.

Evidently, the MDX was designed for premium [manual suggests this]. Beyond this, where do we go from here?

I will continue to run premium until information comes out that suggests less is OK? Don't know how long we'll have the X, but it could be a while.
 

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Hi Srpbep:

___Because American Honda recommends using Regular unleaded in the Pilot and Odyssey vs. recommending Premium unleaded in the MDX for an engine that for all intents and purposes is the same in terms of performance in both vehicles. Only when towing heavy loads does the Pilot get the Premium recommendation. Does it make sense to waste 10 – 15% on fuel if you don’t need it? Does the X’s engine need Premium unleaded to produce the same 240 HP at WOT (wide open throttle) whereas the Pilot does not? That is why the discussion continues to pop up. Acura’s recommendation may mean nothing in light of the recommended fuel for the recently released Pilot.

___Until I see significant differences in timing advance charts as described above showing me the X needs Premium for general use, I will use only Regular unleaded and save $0.20 per gallon for the hundreds to just over a thousand of dollars of savings over the life of the vehicle. That pays for over a year and a half of auto insurance in my situation. MPG effects have yet to be proven one way or the other either.

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 

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Discussion Starter #6
xcel said:
Hi Paul123:

___In your fact #1, you still fail to give the reasons for the Pilot using Regular unleaded yet achieving almost identical HP and Torque ratings. I would say the article you quoted is passing along more myth than fact in the case of the X.
The only reason I posted was that in my opinion the design of the MDX requires a minimum of premium to run properly. I do agree that excessive octane is a waste but I do feel that the engine was designed to run on at least 91 Octane. If the engine wasn't designed for premium, I would totally agree with you. If the manual or Acura didn't say that premium was a must, they I would agree with your article also. The pilot was not designed for the premium, therfore that vehicle has the option of both fuels, but premium might be excessive for the pilot. Just my opinion, and an opinion I found from an AOL writer.
 

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Hi Paul123:

___Pretty amazing that the Honda engineers that designed the X and Pilot engine with their 240 HP, 242 vs. 245 Ft-lb’s of torque, at a 10: 1 compression ratio decided the lower cost Pilots engine should get the 87 Octane recommendation and the MDX to get a Premium recommendation, don’t you think?
Originally posted by Paul123
The only reason I posted was that in my opinion the design of the MDX requires a minimum of premium to run properly.
___Except the X does not require Premium nor has it been shown to date that it runs any better on it. If the engine was designed for 91 Octane, why is it only a recommendation in the manual while the Pilot runs on 87 Octane and has just as much HP while using unleaded Premium as the recommended fuel of choice? The two compression ratios are the same so what gives? According to the article I quoted above, only with knock, knock at WOT, or when pulling heavy loads is a higher Octane needed. I personally have not read that the Manual says the X’s engine was designed for Premium nor does it say it is required. It only says that it is recommended. With the X’s or Pilot’s CAM grind not being a factor in terms of knock, it is my opinion that you are throwing $3.00 - $4.00 to the ground of the filling station at each and every fill up. Given the Pilot’s engines specs at the same compression ratio are almost exact to that of the X, I believe that the AOL Auto writer’s article is incorrect in the case of the X. That is unless you have heard knock at WOT or otherwise while using 87 Octane in your own X? I will be very interested to see those timing plots by someone with the OBD-II HW/SW setup we talked about in the last thread dealing with the Premium vs. Regular issue for the X. Until then, it is a waste of money IMO.

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 

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Recent experience with mid-grade gas in the MDX

The other day I was almost out of gas and the gas station was out of premium, so I put the mid-grade in. This was about 7/8 or more of a tank.

I've never put anything but premium in the MDX before. This was at about 8500 miles on the odometer, about 1000 miles after the first service.

Mileage went down a little more than 1MPG (as measured by dividing actual miles driven by the # of gallons to fill up, not the trip computer. That's a little more than 5% drop, with similar drop in price per gallon. In other words, dollars per mile was the same.

I didn't notice any difference in performance. (I'll be filling up with premium whenever it's available, FYI.)

One interesting note: the first trip immediately after filling up with the mid-grade registered 25MPG on the trip computer (trip is about 20 miles)! This is a trip I make all the time, and normally the trip computer indicates about 20MPG. HOWEVER, we all know the trip computer isn't really accurate -- to get the real data you have to finish the tank and calculate "by hand." As I noted above, the true mileage on the mid-grade was lower. I think the trip computer got a "blip" based on one of the variables changing drastically when it got "new gas."

As someone who does machine controls and software for a living, it sure would be interesting to find out what algorithm it uses to do the computation...
 

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Hi Jonnygoodboy:

___I believe the algorithm uses the fuel injectors instantaneous pulse width as well as actual miles per hour as calculated from the RPM and gear that the X is in.

___As for the gas mileage, unless the timing advance changed between the two fuels (this is what I am really looking for), the lower grade actually has more power available per gallon although this shouldn’t make a difference. I can’t wait till someone posts the timing plots and I hope you can possibly follow through with a two complete 89 vs. 91 tank test or similar as 1 mpg less from the 89 and than 5 more from 91 afterwards is very suspicious … Could you possibly do a much longer 87/89 vs. 91 test. Like a few tanks? I will find out for myself with the 03 but 5% less MPG is a bunch given the Pilot numbers.

___Thank you for the real world feedback.

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 

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xcel said:
...I hope you can possibly follow through with a two complete 89 vs. 91 tank test or similar as 1 mpg less from the 89 and than 5 more from 91 afterwards is very suspicious
Hi ___Wayne,

I've edited my post you were responding to, hopefully making it more clear. The trip computer blip up to 25MPG was immediately after filling with 89, not on switching back, which seems to be what you thought. The extra 5MPG was just a figment of its imagination, since the final hand-calculated mileage was actually lower than usual (for the same driving, route and conditions).

So, to re-summarize, 89 octane provided ~5% less mileage for ~5% less cost.
 

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Discussion Starter #11
Updated Documented Gas Opinions

Just picked up on the canada website for the Acura MDX that it was optional for the premium gas. I stand to be corrected! Regular gas can be used without damage to the engine only a loss of power and gas mileage. I try to pick up the link and post it.
 

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Discussion Starter #12

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The info provided by Paul123, actually found by Paul123 and PROVIDED BY ACURA, sure seems to indicate that Regular is OK.

What do people think of the "new info" [new because Acura has said it] ????


PS -- Paul123 ... ya done good AGAIN!!
 

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Hi Paul123:
Just picked up on the Canada website for the Acura MDX that it was optional for the premium gas. I stand to be corrected! Regular gas can be used without damage to the engine only a loss of power and gas mileage. I try to pick up the link and post it.
___So how many times does Acura have to tell you that Premium unleaded is only recommended? It has been posted in the 01, 02, and now even the 03 MDX literature. Secondly, where did you find out that Premium results in a loss of mileage? Acura can’t tell whether the 01/02 MDX has 242 or 245 Ft-lbs of torque let alone show anyone any specific differences between using Premium or Regular unleaded yet they mention loss of power … I guess all those Honda Pilot and ODY owners are suffering a loss of their 240 HP spec because they don’t have to use Premium except when towing something heavy as per the manual …

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 

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xcel said:
Hi Paul123:

___. That is unless you have heard knock at WOT or otherwise while using 87 Octane in your own X?

Until then, it is a waste of money IMO.

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
Hey Wayne-

Will you actually HEAR knock?

Especially if the knock sensor detects knock and retards the timing virtually instantly ?....
 

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This is an interesting debate. How indeed does the identically spec'd Pilot engine run on regular when the MDX's runs on premium? One guess is that the Pilot specs are done on premium gas, but that both engines have sufficient range in their advance maps (in the old days, it was only an advance "curve"; today's computers can do much more than plot a curve) so as to accommodate regular. The true test would be running several tanks of one grade versus the other, in one of each vehicle, driven the same route for several weeks to see if there is any difference in fuel economy. If the MDX's engine is tuned to max out with premium, then running it on regular should show a decrease in mileage (as well as power, but that might not be as noticeable). If the Pilot was similarly tuned (my theory that they achieve pwr rating spec using premium), then mileage should similarly suffer on regular. If there is no difference running regular vs. premium, then the maps are maxed out on regular, and those of us using premium in our X's are indeed wasting money. So, who wants to volunteer to do this test? :4:
 

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FWIW the engines aren't entirely identical. The VTEC implementation differs.

And the torque band is flatter/broader (e.g. @ max torque) on the X than on the Pilot.

(from autofieldguide.com)...the Pilot team's job was to replace some of the premium elements of the MDX's excellent 3.5-l V6 and tune the powerplant for fuel economy and smoothness as opposed to off-the-line performance. The three-rocker setup for the variable valve timing system was replaced with one based on two rockers per cylinder, and the dual stage intake system was jettisoned. In its place a new intake and exhaust system was developed by Honda R&D Americas (Raymond, OH) to optimize the power characteristics of the modified engine. (Though Honda has stated in the past that it has no intention of moving fundamental engine development outside of Japan, this project clearly shows that the powertrain staff in Ohio is increasing its capabilities.) According to Paluch, "The low- and mid-range rpm are completely different than the MDX, which has a flat, broad torque curve. The Pilot's torque curve is more gradual but it peaks out in the same area." Knock sensors were also adjusted so the new SUV could avoid the premium fuel diktat of its upscale predecessor
 

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Hi Ardvarkus:

___That is why we need the timing plots … There was someone posting into this forum a few months ago that thought the X as well as many late model Honda’s did not use KS anymore and simply relied on the timing plots to keep the engine out of harms way. With The Worm’s post of last evening, at least that one idea was put to bed.

___As far as performance, with Acura’s recommendation of Premium for the X, what is Acura telling you? Regular unleaded is most certainly fine. I can’t wait to see those timing plots to prove it one way or the other.

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 

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Whew

If this has already been suggested, forgive me I haven't read everybody's replies yet, but this just dawned on me.

Is it possible that the 91 octane was recommended for the MDX because they wanted to give it an added air of luxury? Since running the MDX with more than needed octane is relatively just a small waste of money (yes I know it adds up) and does no real harm to the engine, maybe the subliminal sense that you are filling up with the "premium" octane instead of the "regular" goes a long way to feeling more set above.

Particularly seeing how the Pilot and the Odessey have (give or take) the same engine as the MDX but come from the base line Honda brand. I'd say ride for a week with the mid grade octane, then try another week with the lowest grade and record what differences you notice. If I had my MDX I could have told ya'll definitavely by now, because I would have done the experiment long ago
 

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experiment design

MK23666 said:
I'd say ride for a week with the mid grade octane, then try another week with the lowest grade and record what differences you notice. If I had my MDX I could have told ya'll definitavely by now, because I would have done the experiment long ago [/B]
Better yet have someone else fill up the tank for you (2 times) without telling you what grade of fuel was used. Reveal the fuel grade that was used only after all notes/impressions are recorded.
 
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