I don't want to spark another thread of "if you bought luxury should be able to afford premium" so let me start with a good ol' disclaimer: this is NOT about performance. In a little devate with 4thaccord flaunting the "higher ownership cost" against the tlx got me to look a little deeper into the "premium vs regular" but with a little more practicality added to it.

The full article is here but here is the rundown.

We understand that buying octane fuel higher than recommended in the car manual won't bring any more benefits from it (source: Cartalk)

and because those who have done the research know that premium gas for the TLX is recommended and not required (source: Mat Hargett, Vice President of Acura Development & Chief Engineer, Acura TLX at Autoline After Hours 262)

this translates to me as TLX owners having the option to go back and forth between fuel types, but for what purpose and what cost to performance? that's where the article makes a practical approach:

[quote]

The next step is to compare the prices of ethanol-added fuel and non-ethanol fuel. You’ll need to know the prices to figure out which is the best buy – but it’s not always the cheapest one.

The Department of Energy suggests that 10% ethanol blend fuels trim about 4% off of the gas mileage of the automobile. My experience actually pushes that percentage higher – according to my own measurements in our automobiles, doing a mix of city, interstate, and highway driving, 10% ethanol blend fuel drops gas mileage by 7-8%. Let’s say it’s 7.5% for the purposes of calculating this.

What I do is I take out my calculator on my phone and multiply the non-ethanol fuel cost by 0.925 (which is simply 1 minus 0.075 – the 7.5% indicated above) and see what the resulting number is. If that number is lower than the cost of the ethanol fuel, I buy the non-ethanol fuel. If the ethanol fuel is still cheaper, I buy the ethanol fuel.

[end quote]

The article goes on to say that most of the times the writer tends to buy ethanold-added fuel because it's till cheaper even after calculating the reduced efficiency and that prices between the two types will vary by season.

In my research about ethanol showed that law requirements have varied wildly from state to state and that in most metropolitan areas your choices will be limited to only ethanol filled gas. Either way, I am understanding then that it is perfectly possible to make a calculated choice for your gas type based on the prices at the gas pump even if all three of the gas have E10 marked for 10% ethanol however that's not my main point.

The point I'm trying to make here is actually much simpler: our engines are far more flexible than our 87octane only siblings thus we have a greater range of driving choice from hyper miling to hyper revving given our various and unique driving situations. I'll take that as a win, even if all this is theory until we see some miles in our TLXs.

 

Fuel aside, lets talk about an issue with Direct Injection; Carbon Buildup. With no fuel being sprayed in the ports carbon buildup occurs on the valves and can cause some issues later on in life (100K+ mile point).

The poorer the fuel you use, the more buildup you are going to experience. Also the car's longevity will suffer as well. Yes the engine can adjust timing for different fuel grades, but the 3.5L engine is high compression requiring at least 91 octane to prevent knocking/detonation. The J series is prone to knocking with poor fuel quality.

I get about 2MPG less going from 93 octane to 92 octane in my 4G TL and the same in my 3G TL. Going from 92 to 91 octane leads to another 1 MPG drop. I've had a rental TL that the sales staff filled with 87 and the best MPG I could squeak out on the highway was 4MPG less than my average with either my 3G or 4G TL.

These are high performance engines and for optimum fuel economy you want to use the highest available octane with 95 octane really being the upper limit for the TLX in it's factory form.

I've paid $2.79 for 93 Octane E10 fuel this week and have got an average of 25MPG. If I'd gotten the 87 for $2.59 I would have gotten a free gallon of gas (savings of about $2.59 on a whole tank). 4 less MPG means 21MPG. 21x 10 gallons is 210 miles range vs 25x10 which is 250 miles. A extra 40 miles and that's more than what you'd get for free from using 87.

 

I get on average about 40 - 60 miles less per tank running 87 vs 91-93 in my TL. It costs me more to run regular than it does premium. I get about the similar drop in the winter time with the winter blended fuel.

 

There's only one place in Houston to buy non-ethanol gas and it is about 40 miles away. I wish non-ethanol was an option. I hate that ethanol stuff. What a ridiculous political idiocy to put our corn in our gas tanks.

http://pure-gas.org/index.jsp?stateprov=TX

 

Well they wanted to add something, and ethanol is thought to be safer than other options.

 

If you'll ask how is the weather? Someone from Alaska will say that it mostly freaking cold while someone in from Florida will call it a bs because it is always hot.

Answer to original question depends on number of conditions. Since air to fuel ratio is 14:1 it mostly depends on outside temperature and on knock sensor. I think that some knock sensors are more sensitive therefore you might have two same cars that will end up having different results just because of different years of production (updated parts and software).

Here are results for Acura TL 2008. I did this test about 6-8 months ago just to satisfy my own curiosity.

3 consecutive fill ups with 87 with outside temperature below 75 degrees resulted in gain of about 1 MPG all this time I ran with a scanner and there was no report of timing being pulled under normal driving conditions. Only at WOT with RPMs above 4600 timing was pulled by 1.0

Some other things to conciser:

87 and 91 have exactly same energy content neither burns hotter, faster or produces more energy.

Some fuel makers claim that their premium gas has more detergents and additives. I am not sure how to verify this claim. I was due for a smog test during my experiment and running on 87 smog check was reporting close to zeros across all categories I do not think I'd get any better results using 91.

What sparked my curiosity is that my wife's car Lexus RX 330 with 10.8 compression requires 87 wile my car with 11.0 compression requires premium. I switched my wife's car from 87 to 91 and surprisingly her car lost about 1 mile per gallon.

I did a retest with outside temperatures close to 90 degrees and still didn't have any timing pulled under normal driving conditions but I noticed that after a short stop like at the ATM or get a cup of coffee on initial crank I could hear for a split second and scanner would report that timing was pulled. I think it is due to air inside intake manifold and under the hood is being much hotter than the outside.

 

I have driven a 2007 RL 170,000 miles before selling using the middle grade 89 octane and 75,000 miles on my 2010 RL and again have never had a problem. I would however not go to the 87 octane. I have noticed no difference in gas mileage when using premium. Save your money. I looked for two M.I.T. graduates opinion which is linked.

Premium vs. Regular | Car Talk

Another opinion:

Save Money and Stop Buying Premium Gas

From Car & Driver:
Our tests confirm that for most cars there is no compelling reason to buy more expensive fuel than the factory recommends, as any performance gain realized will surely be far less than the percentage hike in price. Cheapskates burning regular in cars designed to run on premium fuel can expect to trim performance by about the same percent they save at the pump. If the car is sufficiently new and sophisticated, it may not suffer any ill effects, but all such skinflints should be ready to switch back to premium at the first sign of knock or other drivability woes.

From USA Today:
The main advantage of premium-grade gas is that it allows automakers to advertise a few more horsepower by designing and tuning engines to take advantage of premium's anti-knock properties. But auto engineers generally agree that if you use regular in a premium engine, the power loss is so slight, most drivers can't tell.

"I go back and forth, and I'm hard-pressed to notice" whether there's regular or premium in the tank, says Jeff Jetter, principal chemist at Honda Research and Development Americas. He drives an Acura designed for premium.

Import brands, especially, use premium fuel to distinguish their upmarket models. Most Toyotas, for instance, are designed to run on regular or midgrade, while the automaker's Lexus luxury brand prefers premium. Same with Honda and its Acura luxury line.

"Generally, the more expensive the vehicle, the higher the expectation for performance and the more the customer is willing to pay for fuel," says Pete Haidos, head of product planning for Nissan in the USA.
__________________

 

 

I recently took my engine apart and had MAJOR carbon build up on my pistons.
likely from poor gas.

 

All it comes down to is if your car doesn't require PREMIUM, there is not benefit in putting PREMIUM.

If your car requires PREMIUM, you put in PREMIUM. What's next? Getting only liability insurance on a new car?

I'm still owed a full tank of gas due to bringing in my vehicle for a recall and my tank was already full. Been to lazy to go back to get the refill. I have until Feb though I think. (Infiniti).

My car is leased, but I still use premium because that's what is required. Not sure why on every forum, there are people who who have nice car that use cheap gas, and people with crappy car who use premium. LOL

 

I don't want to anger the forum gods by casting doubt on something a Moderator says, but I find it completely unbelievable that you see a 2mpg drop by just going from 93 octane to 92 octane gas. In fact, the octane difference between the two (about 1%) is statistically insignificant and within tolerance error at the refinery, so the two fuels are essentially indistinguishable from each other.

Also, since octane is just a measure of knock resistance (and not energy), your car wouldn't know the ~1% difference, and a drop in mileage of roughly 10% is all but impossible. Something else is involved.

Ditto for the drop on mpg from 92 to 91.

Sorry, but I respectfully call BS.

.
.

 

+1

 

Top Tier gas are supposed to have the same detergents for all grades.

 

Besides Audi and Toyota, who else have done workarounds like adding a second set of port injectors?

Should You Buy a Car With Direct Injection? » AutoGuide.com News

 

On the right side of the page there is link to pdf file that will provide you with some technical information.

Fuels | Products & Services | Chevron


This is from the page 81

"REQUIRED ADDITIVE USE
As a result of the relationship between decreased deposits and decreased emissions, all motor gasoline sold in the United States must contain an additive that provides a minimum level of deposit control performance. This requirement was established by the Clean Air Act Amendments of 1990 and became effective in January 1995. A similar requirement has been in effect in California since January 1992. Additive manufacturers are required to obtain U.S. Environmental Protection Agency (EPA) certification for their additives. Each certification request must include documentation of the additive’s effectiveness in specified fuel injector keep-clean and intake valve keep-clean tests (see sidebar) when evaluated with specified test fuels. A similar detergency requirement exists in Thailand. Before selling any gasoline in the United States, gasoline marketers must add a certified DC additive to their gasoline at the certification concentration level or higher. The minimum certification concentration level is referred to as the lowest additive concentration, or LAC. This dosage is not very effective in controlling deposits in certain fuels and engines. Higher concentrations provide improved performance, such as the ability to change keep-clean performance to cleanup performance. Historically, some gasoline brands have provided much higher deposit control performance than the minimum level of certification performance required by the U.S. EPA. For competitive reasons, they probably will continue to do so.


TOP TIER DETERGENT GASOLINE
Six of the world’s major automobile manufacturers, BMW, General Motors, Honda, Toyota, Volkswagen, and Audi, believe that detergent additives used at the U.S. EPA’s minimum certification level, LAC, do not provide sufficient deposit control to help enable optimal engine performance. To inform consumers of the higher level of performance these automakers believe is needed, a further gasoline/ additive qualification system has been developed and covers:
• Intake valve keep-clean
•Combustion chamber deposits
•Fuel injector fouling
• Intake valve sticking

Gasolines that meet the standards qualify to be categorized as TOP TIER Detergent Gasoline. The engine tests required by the standards (see sidebar) provide a more stringent assessment of additive performance than U.S. EPA certification. In addition, TOP TIER Detergent Gasoline is not permitted to contain metallic additives, including methylcyclopentadienyl manganese tricarbonyl (MMT)."

 

They have required minimums across all grades, so the Premium may still have more.

Even with non top tier fuels, the premium grades probably meet the specs, but if their regular doesn't, they don't get the top tier label.

 

Everyone is entitled to have their opinion and to call BS!

I've driven the same route for the last month in my 4G TL (336 miles each way) using gas from the same 2 gas stations. 1 Gas station is a privately owned one which sells 87, 89,91,93 octanes and E85. The other one is a truck stop that carries 92 Octane, 87 and 89.

I've used manual calculations over highway driving along with the trip computer and they have verified it. I've had the car loaded with 2 passengers and used cruise control on 72MPH.

Perhaps the 92 octane had more ethanol blended in it or it was "stale"/older than the 93 I got. In any senario these are my real world results from driving back and forth for the past month and putting 2K miles on the 4G TL.

Also I want to add that the J-Series engine is prone to knocking and detonation, esp after heatsoak and the timing is reduced once it starts picking up on it. The difference in 92 and 93 may cause less knock and therefore advance the timing back to where it should be. This timing difference could be the reason why the highway MPG changed so much as the engine is turning over at around 1800-1900RPMS. I'm going to pick up a reader soon so I might be able to read these values while driving to see how the octane really effects timing with 93, 92 and 91 octane.

 

Another unscientific study: When we had a '99 Accord 4-cyl., I bought the cheapest gas. The throttle stuck until I pushed hard enough. Two expensive injector flushes later, I switched to Shell, QT, Exxon and other name brands. Zero problems after that. So in both our TLX and RDX it's regular the way. We get enough performance out of regular for the occasional on-ramp or traffic light adventure.

 

I have a 3.5L TLX Loaner until tuesday! So far on the way down to work (336 mile journey), I got 36.5MPG (according to the MID) doing 70-72MPH on cruise with 92 Octane from the same truck stop that I go to. This was in Econ Mode. I'm going to update with the return trip and 93 octane.

 

"Our tests confirm that for most cars there is no compelling reason to buy more expensive fuel than the factory recommends, as any performance gain realized will surely be far less than the percentage hike in price. Cheapskates burning regular in cars designed to run on premium fuel can expect to trim performance by about the same percent they save at the pump. If the car is sufficiently new and sophisticated, it may not suffer any ill effects, but all such skinflints should be ready to switch back to premium at the first sign of knock or other drivability woes. And finally, if a car calibrated for regular fuel begins to knock on anything less than premium or midgrade, owners should invest in a tuneup, emissions-control-system repair, or detergent additives to solve, rather than bandage, the root problem. Class dismissed".

For mist of us, I believe this final paragraph from a Car and Driver article on using different Octane rated gasolines is a good summary of the issue. From other reading, it would seem reasonable to suggest that higher compression Direct Injection engines like the 3.5 on the TLX do better in regards to both performance and longevity. Perhaps a little mixing from time to time, depending upon gas prices isn't a bad overall strategy either.

 

This particular debate always cracks me up, particularly when you see it on forums of upscale and/or performance cars. The folks have already made an economic decision to spend more on a car for various reasons and, in some cases, it could easily be thousands more.

So do the math. Assume you drive 10,000 miles a year and get on average 20 mpg. That works out to about 500 gallons of gas. Assuming the premium is maybe 20 cents more a gallon than the regular you are looking at $100 more a year. I realize that any benefit to using the "good stuff" might be hardly measurable, I always end up putting the premium in all the cars I have owned.

 

Thank you for putting this issue in true perspective! Math doesn't lie

 

You're welcome! Amazingly I have also seen this discussion on the Corvette Forum as well as other performance car forums.

 

It's funny how some people shell out $40K for a performance car and then complain about spending a few hundred dollars more a year for premium fuel.

Gas stations around here don't typically sell 91 octane, so I use have to use 93. At one point I was paying $4.70+, but this week it's under $3.00!

 

This is the first time in a long time that one of my unwritten rules of gas prices did not come to pass. That rule was that when gas prices started lowering noticeably, there was always some "incident" that halted the decline such as some natural disaster somewhere, problems in the mideast, oil embargo, refinery fire, refineries down for servicing, etc. This halt in the price decline never seemed to fail over the last few years--whenever prices would drop below $4.00 they seemed to pop right up again based on some contrived reason. But this time is different--which pleases me.

 

The down side of low gas prices is that it actually hurts the jobs sector that are based on oil and gas. They are expecting massive layoffs here. OPEC is doing it's best to shut us down. It's all manupulation

I always wondered why the price per barrel was ever as high as it was in the first place. It's around $50 now but was up to near $120.

 

Next thing we'll hear about is a guy crashing his car and only having liability, oh, and the car is also leased and it's supposed to have full coverage. LOL

 

Correction, This debate has been beaten to death on all automotive / enthusiast forums. Yes, Including this one as well. The logic is straight forward. Using highest octane has benefits, PERIOD. The difference in the amount of money spent in year from regular to premium is barely noticeable in a weekly budget, and even more so in the year. 100-200 dollars spent more is not going to magically save you a ton else where, especially not in maintenance cost's in a vehicle.

My wife has a new Kia optima with the direct injection engine. It says to use regular, and It's never seen regular since the day it rolled off the assembly plant. I've always put 93 in all the vehicle's I use. Even more so in my TL which is supercharged. Now that gas prices have fallen, there is no excuse why premium isn't used. It's disgusting, how many higher end vehicles are jam packed at Delta gas stations because 87 is nearly 1.98 but premium is much higher compared to other gas stations. As a certified technician for over 10 years, I've done enough in my life of pushing wrenches to know the out come of long term poor gasoline use vs premium.

Hell, I can even get 100 octane unleaded clean gasoline at my local Sunoco. I've used it for the summer seasons with my TL to help control Knock, due to heat and being supercharged. Bitch about those prices at 9.89 a gallon, though, now it's 7.99 a gallon.

 

I agree with the above. I did not mean to imply that this was not a typical topic of discussion, only that it is more ironic when you see it discussed at places like the Corvette Forum.

In addition to always using premium (which I understand might be a waste of money), the other thing I occasionally do is to pour in additive to the gas tank every so often. I realize this might just be a "feel good" thing but I figure it can't hurt if judiciously used.

 

Subaru requires 87 and it runs just fine on it.

CL type S requires 91 or higher so it gets it. I have used 89 a few times when 91 was not available and yes I noticed the drop in mpg from doing it.

 

Majofo: "Again..

Sure some places are going to have a big differential, but that doesn't mean you need to fill up there. Most of the nation sees a much smaller differential. The price differential from the lowest for regular and the lowest for premium is ~0.30 there.

Gasbuddy / chicagogasprices / gaspricewatch all list reasonable prices for premium across Chicago."



Again... I stand by my numbers. In my zip, the lowest reported 87 is $2.19, vs the lowest premium of $2.74. A 55cent different can give much different results that the 20cent many people keep using in their examples.

Sure if I lived in an area that had it, paying 20cents extra seems to be a no-brainer. I'm moderately "ok", paying the 45cents extra I've been paying now. But if that delta continues to rise, and premium starts costing 70cents-$1 extra as I have already seen at some stations, I'll probably drop down to midgrade or regular. I don't think the lost mpgs would make up that difference.

 

Do you think they're trying to shut down the frackers by bringing the price lower than their alternative? Or do you think OPEC is trying to drive Putin into the ground with low prices? If the latter, would they (Saudis?) be doing it at the US direction?

 

That is an angle I hadn't thought of. My company does a lot of work for ExxonMobil in far eastern Russia (Sakhalin Island). it would hurt to lose that chunk of contracts.

Rumor has it that the Saudis et al. are trying to squeeze out countries like Venezuela because they have been undercutting prices for quite a while.

 

It makes you wonder who has the lowest prices (labor, infrastructure, labor etc) to get the stuff out of the ground? IOW, who can sell oil at $45 per barrel and make a profit? Especially when you factor exchange rates etc.

 

Considering that fellow members have measured preignition with 92 at idle on the J35, and that conservative estimates using the physical dimensions of our engine and CR put us in an octane rating in the mid to upper 90's to prevent knock, would point that on premium our engines might already be pulling timing. So a drop from 92 which is at the edge of the spec, especially for a heat soaked engine that cs might encounter regularly in FL traffic, is not at all implausible that he's seeing a 10% drop in fuel efficiency.


Several things irky with your calculation, so let's restart. MPG rating for the TLX is something between 24 and 34 correct? So let's say 28 mpg to be conservative. The average motorist in the TLX age group travels about 15k miles a year. That equates to 535 gallons a year at 28 mpg. If we estimate an avg cost of premium at $3.80 / gallon for the year, that's $2033.

What you didn't calculate was the lost mileage due to the use of regular. You're going to see a significant drop in mileage. Because you're now spitting excess fuel down the pipe dropping your mileage and performance because your PCM has pulled timing to keep things in check. A 2 mpg cost is now roughly 577 gallons a year. If the avg cost of regular is $3.50 / gallon for the year, that's $2020. Now if you see a 4 mpg drop, that's $2187.

You can adjust the values to your situation, but what you'll see is that you're really not saving much money at all, and in the long run, you're losing money. This is a conservative estimate as well.

Consider that the excess and unburnt fuel is now damaging your primaries.. Want to guess how much it costs to replace your primaries / 3rd cat? It's not cheap.. but then you say, well I'll just straight pipe it or core them out. What about the damage to the engine over the long run? It's not worth it to skimp at the pump. If you guys really want to save some money, try to keep the revs low and your highway speed reasonable. Big mpg difference between travelling 60/65 and 70/75.

Btw.. that Edmunds article and others are garbage.

You should find somewhere reasonable on your commute that offers a lower price alternative that is in the top-tier. Especially if you're in a lot of stop and go traffic. Your engine will see the most wear and tear. There are some big differentials in the Chicago area but I'm sure there's still an affordable option for you. At least you don't have to pay as much as the canucks. The closest station to me is one of the highest in my area. My commute is long so I fill up at the station closer to my work. Affords me a cheap cup of coffee a day.

 

Lol, we produce the shit and the cheapest 87 we have here is like $2.55/gal, and that's at Costco. Most other stations are $2.83/gal

 

 

Funny thing happened to my wife yesterday. She was reading on the other fuel thread (Thanks to MR. Hyde for cleaning it up), she called me and said "My Co-workers said Costco has regular for $1.81" in which my wife says "I don't use regular, I use 93 octane" to get a reply of "Must be good to be rich"..

You can't make this crap up anymore. The lady who told her this owns a 2013 C350 Sport 4 matic. At the end of the day, no matter what points are being proved, regardless who says it, regardless of research and facts, people will do what they want to do and rightfully so.

 

The stupidity of people never ceases to surprise me.. I have family members who have given the same sentiments.. you can't chose your family.

 

I wanted to be intentionally pessimistic on the calc just to show that the actual number under the worst assumptions is not worth worrying about.