Regular Or Premium Unleaded Fuel?

[im184jcs92]

I say use whatever gas octane you either 1) can afford or 2) how much you're willing to pay. I fill up with rotating on Octane 87 and 89 gas just becuase I don't want to fork over $2.50 a gallon. Dang gas company and gas station owners trying to rob us hard working consumers.

And as usual...I know this is going to hurt some people but.....[B]GAS IS GAS PEOPLE!! IT WILL RUN YOUR CAR EITHER WAY!! :D

Remember: The faster you go, the more gas you burn, the more money you burn.

So, ease up on the speed, ease up on the octane level and treat yourself to nice steak dinner with the money you save.

[GI_Jim]

Just as a note guys, be sure that your octane rating does NOT include MTBE or Methanol which are just additives and can reduce the energy value of the fuel.

I found this article also and I can relate to the part about how higher octane means less power. I hap a 94 S-10 with a 4.3 V6 CPI and tried running 93 when it called for 87. The 87 definitley gave me more power from the engine. Also as a guess from me couldn't you just take same amounts of both types of gas, burn them in a beaker or some other way and then determine the amounts of carbon and debris produced to see if there really is a quality difference? N E way here is the topic.

August 27, 2003

“I only use super/premium/performance/ high octane fuel in my Civic DX. I can feel the power…”

This is probably one of the biggest misconceptions in the automotive world, as we know it. Yet, I hear this all the time. For example a close friend of mine who drives a 1996 Pontiac Bonneville tells me that he only uses Chevron 92 octane fuel because “It performs so much better, and my fuel economy is way higher.” This opinion or misconception is not an isolated view to the “gear-heads” that are or think they are car savvy. And the oil companies don’t help the matter by calling their high-octane fuels “Performance” or “Premium,” or whatever they choose. Here is why.

The first thing we have to know is obviously, what is octane and why does it matter? Octane can be simply defined in one sentence: Octane is a rating of a fuels resistance to ignite (evaporative qualities). WAIT A MINUTE! Resistance? That’s right, resistance. To put it simply, the higher the octane, the harder it is to get to ignite. Higher-octane fuel resists burning. Lower-octane fuel does not. Lower-octane fuel is actually more explosive, move volatile, and creates a much bigger explosion then its higher-octane counter-part.

When you go to the pump to fill your car, you generally have three options. Regular, mid-grade, and super. You also see that there is a rating system. It is a sticker posted to the pump next to the octane rating of the fuel that you choose. It generally says something like this. Regular for example: 87 Octane minimum, measured by using the (R+M)/2 rating. What does this mean? The R in the equation stands for Research Octane Rating, known as RON. This is a test that tries to simulate variables that your car would go through on a given day. It is a test using a single cylinder, four-stroke engine that is idling at 600rpm. The fuel temperature going into the engine is not controlled. It is allowed to vary and fluctuate with the temperature of the conditions at the time. The intake air temperature is varied with barometric pressure to simulate the air being sucked into the car from the outside. The timing is set at 13° BTDC. This is done to covert everything to a SAE standard day, which is 60° F, 0% Humidity, and 29.92 inches barometric pressure.

The M in the equation stands for Motor Octane Rating, known as MON. When testing MON, the fuel is heated to 300° F and the intake air is heated to 100° F. The test engine is a single cylinder 4-cycle engine that is run at 900 rpm. Ignition timing is varied with compression ratio. Engine load is varied during test. If you are deciding what fuel to use on a high-compression, high-performance engine, this is the test you would want to use. The RON will always be higher than the MON.

So what does this all mean when you go to the pump? It means that to extract the most from the car that you are driving, you have to use the appropriate octane fuel or the car is not going to perform up to its potential. Either the fuel will burn too slowly, and in many cases not burn completely, or it will burn too fast and out of control. The latter is called Detonation. Normal combustion will take place at a pretty steady rate (for a given rpm and load), when a large amount of the charge burns extremely fast and uncontrollably, it is know as detonation. Detonation can destroy an engine in a matter of seconds. There are a few causes of detonation. Usually it is attributed to too much heat, but that is only part of the problem. Pressure and advanced ignition timing both play a role in it too. Usually when detonation takes place, the detonation occurs on the intake side of the chamber, which is the coolest side of the chamber. This happens because detonation did not occur until the pressure got excessive, which was after the spark. By the time that happened, the charge near the exhaust valve has already been burned. Most of the time, detonation will occur after normal combustion has started. Apart from destroying pistons and spark plugs, light detonation can cause all sorts of other problems, like fatiguing cranks and rods quickly and pounding bearings to death, so avoid detonation at all costs.

Another problem is Pre-ignition (for cars using octane that is too low). When the charge lights off before the spark, it's called pre-ignition. This can happen with or without detonation, but usually will cause detonation in a high performance engine. Hot spots in the combustion chamber are the usual cause of pre-ignition. This is very unpredictable and can lead to detonation, because it will act just like too much ignition timing, but it won’t be controllable.

So this is what happens in cars that use octane ratings that are too low, but what about vise-versa? Generally, the problem with using an octane rating that is too high for your car causes problems that, while not generally as severe as going too low, are still detrimental to the performance and efficiency of your engine. One of the most common problems is lost power. Yes, you read that right, if you use an octane of fuel that is too high for your car, you will lose power. This goes for all the stock or lightly modded Civics out there. Remember when we discussed that octane measures the fuels resistance to burn? Well, this is where that really comes into play in a low compression engine, such as the engines found in 90% of all streetcars. As the fuel is injected into the combustion chamber and the compression stroke begins, cylinder pressure is created. This is vital to combustion as cylinder pressure is what translates into power. When that pressure is not high enough (low-compression), the fuel only partially ignites. This means that there is leftover fuel that has to be expelled through the exhaust valves and expelled through the exhaust. This is bad for several reasons. The first is that this un-burnt fuel leaves deposits and grime all over the cylinder and valves. This robs you of power, fuel economy, and wears engine components pre-maturely. There is also a vital part of any streetcar, the emissions control devices. The catalyst for example often is destroyed by being clogged with carbon and un-burnt fuel resulting from using too high-octane. This results in costly repairs, and guess what? The loss of power and lower fuel economy. Not to mention, you had to pay $.20 more per gallon just to lower your cars potential and performance. So you guys that think that adding 100 octane race gas to your Civic Ex at the track is going to improve your times, you are running in the wrong direction unless you have some kind of forced induction such as Nitrous, Turbo, or Super Chargers.

So the next question people ask is, “Why then do high-power, ultra-fast cars use high octane fuel?” Well the answer is simple. Higher-octane fuel contains more POTENTIAL energy but requires the higher heat generated by higher compression ratio engines to properly condition the fuel to RELEASE that higher potential energy. Here is the general rule for choosing octane if you have a question of what it should be. If your compression is 9.5:1 or lower, 87 octane should be plenty. As your compression rises, so should the octane that you choose.

Remember that there are variables to everything in life and this is no exception. If you have dramatically advanced ignition timing for example, high-octane may be needed. But for the vast majority of the people on the street, for optimal performance in your streetcar, use the octane best suited for your car, and remember, high-octane does not mean more power!

Coby Burns (Writer of above topic not forum poster)

Found this at http://www.speedupgrade.com/articles/article/692608/5136.htm

[silkiechicken]

exxon 93 octane @ $1.89 9/10th per gallon

Yeah.. thats alot... 92 octane, Western WA... shell...2.23 per gal and rising

[joeygoodtimes]

it willonly cost on average 2$ to 3$ more to fill up with premium if u aint got that then your in the wrong car figure when gas was 1 dollar for regular and 149 for premium gas really only went up 50 to 60 cents premium or you can buy regular for 1.79 79 cent jump its a premium buyers market baby,some people do drugs to get high, i drive my car.

[BCSC300]

I always used 94 in sc300 and loved it, full tank of gas would last me a little over a week and half. recently Sunco stopped providing 94 at their pumps my probelm is i live in the northeastern part of the country and Sunco was the only provider of 94 octane, would downgrading to 93 cause a probelm? i know of a mom & pops gas pump that sells up to 106 octane, is there quality good enough for my lexus?

[Lexusfreak]

I use nothing but Sunoco Ultra 94 as well BCS, sorry to hear your station(s) no longer supply that octane grade (I wonder why though? ) When I travel to the U.S. I always use either Sunoco or Citgo 93 I find is a good quality fuel. Not sure about the "106" octane stuff from a mom & pop gas station.....if it sounds too good to be true then.......

[BCSC300]

I found out some more info on the mamas & paps 106 octane. Earlier this afternoon i took a walk over to my neighbor's house whom owns a 86' mustang with supercharged 302 which apparently does 10.50 in a .25 mile all he uses is 106 octane in his car. He also mentioned that this is considered race fuel and if anyone even attempted to fuel up with this octane it would burn out their stock fuel injectors. He suggested fueling up with 93 octane then using an octane booster.

There goes an extra five bucks at the gas pump

[1SICKLEX]

I agree with all the posts, I would do what the manual says (min 91 octane) and not listen to what others have done.

Im sure most of us are familiar with SUNOCO gas station, has anyone noticed a difference by using their ULTRA 94 gas, with octane level 94,

rather than any other gas with a max octane of 91 ???

←

We call can run regular gas to make the cars run. To get maximum power and fuel efficiency, you must use Premium!

it's a Lexus, not a Kia. You would laugh at the money "saved" using regular gas.

[RobsES330]

The person at the dearlership told me to use regular. I have not used any other octane since getting the car one month ago. The car has been running well. Perhaps on the next fill up i will try a higher octane.

[1SICKLEX]

The person at the dearlership told me to use regular. I have not used any other octane since getting the car one month ago. The car has been running well. Perhaps on the next fill up i will try a higher octane.

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He probably told u that so u would buy the car. It's a Lexus. It deserves premium. B)

[RobsES330]

Actually I was picking it up that day. I let my wife choose the car, and she did a great job. It was the first time meeting the dealer. He's a friend of a good friend. I got a great deal on the car. His boss didn't want to give the car at the price he was giving. I hope he's still around when my lease is up in 3 years so i can get a great deal on my next one.

[Rich Coleman]

I agree with all the posts, I would do what the manual says (min 91 octane) and not listen to what others have done.

Im sure most of us are familiar with SUNOCO gas station, has anyone noticed a difference by using their ULTRA 94 gas, with octane level 94,

rather than any other gas with a max octane of 91 ???

←

We call can run regular gas to make the cars run. To get maximum power and fuel efficiency, you must use Premium!

it's a Lexus, not a Kia. You would laugh at the money "saved" using regular gas.

←

[Rich Coleman]

I agree with all the posts, I would do what the manual says (min 91 octane) and not listen to what others have done.

Im sure most of us are familiar with SUNOCO gas station, has anyone noticed a difference by using their ULTRA 94 gas, with octane level 94,

rather than any other gas with a max octane of 91 ???

←

We call can run regular gas to make the cars run. To get maximum power and fuel efficiency, you must use Premium!

it's a Lexus, not a Kia. You would laugh at the money "saved" using regular gas.

←

←

[Rich Coleman]

USING ARCO REGULAR: Bought my 92 LS 400 3 years ago [Aug 01] with 145K miles on it and put 15K miles a year of 50-50 freeway-town driving in the San Francisco Bay Area. At the recommendation of Lexus dealer Service Mgr. used Chevron mid grade 89 octane gas containing Techrolene and experienced no knocks, though he personally uses premium. When gas prices soared two years ago, switched to Arco regular [87 octane] and waited for the expected ping and nothing. Not once in two years has it ever pinged like 91 owners have told me.

Having read all postings on this subject, including USA Today article, I'll take my chances on carbon buildup and not interested in more power or increased acceleration. Like other happy Lexus owners, expect to get at least 300K miles before trading off probably for a 93-94. Dislike Generation II's and hate III's.

Anyway, if I don't get 300K will be disapponted, will post mileage results on this site, and the premium club will have a new member. Until then, agree with one owner who uses regular around town and premium for long trips through the mountains.

My 5,000 mile maintenance schedule is simple: Toyota oil/filter change using Chevron 5-30 oil purchased by me as recommended in owner's manual since Toyota uses 10-30 in our area; Big O Tire rotatation; and 12 ounces of Chevron Techroline into the gas tank to keep fuel injectors clean.

At 200,000 mile service, will have timing belt, water pump, and whatever else is included in this package at my independent Lexus repair who uses all OEM parts [$600-700], and maybe fuel pump and fuel filter depending on what he says. The latter two items are on my agenda thanks to Lexus Owners Club.

Just calculated 10 months of gas mileage using ARCO regular 87 octane exclusively [Jan 04-Oct 04] at 19.8 mpg. Lowest was 15.9 in June [hot weather] and 24.1 in January. Without A/C, typical town/highway mileage is consistently 20 mpg ranging between 19-21. With a Lexus mpg rating of 18 town-23 highway, 20 mpg sounds good to me for the San Francisco Bay Area.

How are you doing?

[lancesavage]

I have been using 89 octane in my 2000 GS300 now for 2 years (60K + miles) with absolutely no problem. These guys that rant on about performance, i have not noticed it in my 3.0 liter. I think a lot of this ideaology comes from misinformed dealers fueling the myth that you have to use 91 or better or the motor will blow up. If you speak with anyone involved with the oil industry, they will pretty much tell you, if it doesn't cause knocking or pinging, it ok to use. I have had a friend or two with bigger 8 cylinders (high compression) engines tell me they can tell a big difference when using 91 and then switching to 89 octane. I won't argue since I haven't tested their vehicles. All I can tell you is that my car runs fine. It has also passed the emmissions testing req by our state just fine. Supposedly one reason for foreign car makers specifying the higher octane is that the motor burns it more efficiently reducing the emmissions. Doesn't seem to prove out in my case. Checked compressions and motor is just fine. Good luck and don't believe the octane myth.

Lexus recommends Premium (91 octate) fuel for my "new to me" 2000 GS300.  Anyone tried using Regular (87 octane) or mid-grade (89 octane)?  What, besides pinging could I expect from using the lower prices and lower octane grade? 

I have not seen any posts on this topic before and would appreciate some tecnical as well as non-tech replys.

Thnks.

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[Lexusfreak]

I've compared using Sunoco Ultra 94 vs. Regular Sunoco 87 (Sunoco is the gas I use say 95% of the time) & I found that my power was slightly decreased when I ran several tanks full of regular vs the 94 octane (especially from a stop light & if I need a quick burst of power on the highway). I also noticed that I get overall about 60 - 75 miles extra per tankful on the Ultra 94. So you get slightly better performance using the higher octane (at least I did & it was noticable) plus more mileage out of a tank.......I feel that's worth the extra few bucks per fill up in my books & perhaps even save a bit of money using the 94 over regular when you factor everything in. ;) B)

[smelkony]

When i was using regular in my sc300 i noticed clattering coming from the engine when i was feathering the gas pedal. But now that I have switched back to premium the clattering noise is gone. You will hear the noise going away after 3-5 tankfuls of premium and i will never go back to regular. And of course you feel a difference in performance too.

[Doctor K]

ALWAYS use at least 91 octane i :chairshot: n your Lexus. Here in California we can only get 91. I remember when Union 76 had 104 octane. Those were the days!

[amf1932]

ALWAYS use at least 91 octane i :chairshot: n your Lexus.  Here in California we can only get 91.  I remember when Union 76 had 104 octane.  Those were the days!

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You guys are mixing up the Research Octane Number with the Octane rating. They're two different numbers!

When you go to a gas station the only thing displayed on the pump is the "Octane Rating", NOT the "Research Octane Number".

This is taken right out of my 2003 ES Lexus Handbook:

[chimchim]

Uhhh... Do you guys know why a particular octane rating is even necessary? (let's stick to the Octane Rating stated on the pump, not talk in Research Octane Numbers)

- octane effectively reveals resistance to detonation (burning of the fuel before the spark plugs ignite it)

- the engine's compression ratio (and environmental conditions) determine a detonation point, which means listen to your owner's manual as to which octane to use, as that's what it was designed for.

- exception: in RARE cases, the owner's manual is out of date (happened to Subaru) and a different octane can be found to work as well or better

- for a given engine with a specific compression ratio, as long as you are not detonating, you will get the same power no matter what octane you use

- exception: modern car computers and sensing devices (like knock sensors) are able to detect knocking (detonation) before the driver can even feel it and will adjust the timing (usually !Removed!) to avoid this problem. This protects the engine, at the cost of performance efficiency... which means the driver will feel like his car is "sluggish".

- sometimes the environmental conditions are such that you can use a lower octane gas without problems, but this is not a realable way to go as environmental conditions fluctuate too much.

Bottom line, you best bet (usually) is to stick to the octane rating your owner's manual says to; no more, no less.

[chimchim]

Wow. I just read some more of this thread and it looks like not many people know much about this subject but have a lot of hearsay.

- Higher than necessary octane will NOT harm you car. It merely makes your car's operation less likely to experience detonation. Sometimes additives are only added to the high octane "premium fuels" and that might be considered "bad" for your engine; depending on who you talk to. But this has nothing to do with the octane itself

- "pinging" and "knocking" and "detonation" are all the same thing when talking about engins. The terms pinging and knocking came from the sound you engine makes when detonation is occuring inside the engine.

- Note that combustion is different from detonation. In engine terms, combustion is the ignition of the fuel by spark plug, which is controlled by the ECU (in a fuel injected car). Detonation is when conditions (pressure, temperature) cause the fuel to spontaneously ignite. When this happens at the wrong time (before spark ignition) the piston is still travelling up to compress the fuel. The detonated fuel then works AGAINST the direction the crank is intended to go. This causes massive jarring in the engine (remember, the other cylinders and momentum are working to keep the crank moving in the right direction) and is what you'd hear as pinging/knocking.

if you use higher ocane then recommended your seals will get burned as well due to higher combustion temepratures. it means blue smoke and $$ to waste

Is this a joke? Using higher than needed octane will NOT increase combustion temperatures. There is effectively the same about of energy per liter of fuel regardless of octance number.

If your combustion temperatures are above normal, you're running lean.

If you've got blue smoke coming out the pipe then you are burning oil somehow... which means your head gasket is probably leaking or your piston rings are shot.

[aslexus]

Lexus recommends Premium (91 octate) fuel for my "new to me" 2000 GS300.  Anyone tried using Regular (87 octane) or mid-grade (89 octane)?  What, besides pinging could I expect from using the lower prices and lower octane grade? 

I have not seen any posts on this topic before and would appreciate some tecnical as well as non-tech replys.

Thnks.

←

I would like to know if you can use E85 - 85% alcohol?

[aslexus]

Wow. I just read some more of this thread and it looks like not many people know much about this subject but have a lot of hearsay.

- Higher than necessary octane will NOT harm you car. It merely makes your car's operation less likely to experience detonation. Sometimes additives are only added to the high octane "premium fuels" and that might be considered "bad" for your engine; depending on who you talk to. But this has nothing to do with the octane itself

- "pinging" and "knocking" and "detonation" are all the same thing when talking about engins. The terms pinging and knocking came from the sound you engine makes when detonation is occuring inside the engine.

- Note that combustion is different from detonation. In engine terms, combustion is the ignition of the fuel by spark plug, which is controlled by the ECU (in a fuel injected car). Detonation is when conditions (pressure, temperature) cause the fuel to spontaneously ignite. When this happens at the wrong time (before spark ignition) the piston is still travelling up to compress the fuel. The detonated fuel then works AGAINST the direction the crank is intended to go. This causes massive jarring in the engine (remember, the other cylinders and momentum are working to keep the crank moving in the right direction) and is what you'd hear as pinging/knocking.

if you use higher ocane then recommended your seals will get burned as well due to higher combustion temepratures. it means blue smoke and $$ to waste

Is this a joke? Using higher than needed octane will NOT increase combustion temperatures. There is effectively the same about of energy per liter of fuel regardless of octance number.

If your combustion temperatures are above normal, you're running lean.

If you've got blue smoke coming out the pipe then you are burning oil somehow... which means your head gasket is probably leaking or your piston rings are shot.

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[mikek753]

by the car manual for ES330 - use 86 or higher

I've tried 87 and 91

I haven't feel any performance diff.

where MPG went up from 23.5 to 24.6 (two weeks average, the same drivings)

Now, 91 cost 10% more then 87 and car is getting below 5% MPG economy

If manual states to use 87 then why waste money?

p.s. I use Techron bottle every 5k ml

[lancesavage]

I have a 2000 GS300 and have been running only 87 octane in it since the year 2001 and currently have 87,000 miles on it. Never really noticed a performance issue (come on, its not a 454 hp high compression engine, just a little 6 banger). Just changed the spark plugs and borescoped the cylinders. Plugs really don't need to be changed, just cleaned and regapped, and cylinders/valves look fine.

Conclusion: If you want to spend more money for fuel, go ahead. Its the same as thinking Shell gas is better than BP. Its all the same stuff guys. The reason the car makers tell you to use the high octane is that you get the best (lowest)emmission results. For my money, I will keep using the 87 octane in my six cylinder toyota.