Regular vs. Medium gas in Base

VibeInTx · Post by **VibeInTx** » Fri Jun 27, 2003 12:11 am

Just for kicks, I filled up with 89 octane gas in my base vibe the last couple of tanks, and I swear I can feel a performance difference. The car seems much better on the low end. Has anyone else tried this comparison? I don't think this is due to the psycological effect, because I when I added an Amsoil air filter I was "expecting" a performance increase, but didn't feel any. In this case, the car really does feel better to me with medium.Thoughts?

Robert G · Post by **Robert G** » Fri Jun 27, 2003 12:22 am

It may be just the difference in source of gas, or summer v. non-summer additives. I learned long ago that higher octane than an engine needs does not add anything.

Nervous_Dog · Post by **Nervous_Dog** » Fri Jun 27, 2003 12:38 am

Octane does not add performance. It only prevents detonation or "knock" by allowing the gasoline to resist combustion while being compressed. Check out this link: http://auto.howstuffworks.com/question90.htm

VibeInTx · Post by **VibeInTx** » Fri Jun 27, 2003 1:57 am

Modern cars will not knock. They have knock sensors that will detune the engine's timing. Performance improvement with octane increase is feasible, and I think I have experienced it.

tau166 · Post by **tau166** » Fri Jun 27, 2003 2:20 am

Going more than 2 points over your recommended octane is actually psuedo detrimental. You probably won't hurt anything, but your gas mileage will go down. Higher octane gas has a higher flash point. Your spark plugs are designed to ignite 87 octance gas (in a base Vibe). If you put high octane gas in you actually won't fully burn the charge and your MPG goes down so you're just wasting money. My .02

yank dini · Post by **yank dini** » Fri Jun 27, 2003 2:41 am

yeah I switched from 87 to 93. And there is a diff..... A few folks in here say that it's just placebo effect but I know my baby and she likes 93 better.I dont think I'll go back to 87

VibeInTx · Post by **VibeInTx** » Fri Jun 27, 2003 3:09 am

How is a spark plug designed for a specific octane, exactly?A spark plug provides a spark.

Nervous_Dog · Post by **Nervous_Dog** » Fri Jun 27, 2003 3:53 am

You asked for our thoughts in your original post, but you don't seem to want them if they don't agree with what you think. You aren't going to believe anything we say, are you? Go ahead and ignore the facts and spend more $$$ on gas. It really doesn't matter to me. I was just trying to help.

VibeInTx · Post by **VibeInTx** » Fri Jun 27, 2003 4:10 am

Dog, I'm engaging in a conversation here. Just because you posted one thing that you say is a fact does not mean that the topic is not up for debate. The ECUs compensation for engine knocking has been discussed in these forums before. I understand the basics of octane, fuel compression, and premature detonation. The facts as I understand them are, that in a modern car (such as our lovely Vibe), the computer can detect knocking if it occurs, and adjust the air/fuel ratio and/or spark plug timings to compensate for the premature detonation. In this case, since the computer can compensate for the knocking, the driver will not notice any knocking, but will experience a degredation in performance. I am relaying my experience to the group, that since I put 89 octane in my car, it has "felt" better to me. I am asking if other drivers have noticed similar phenomenon, or can comment on my experience. From what I have heard, the 10:1 (or so) compression ratio of the 1zz is pretty high for 87 octane gas.

yank dini · Post by **yank dini** » Fri Jun 27, 2003 4:14 am

yank dini · Post by **yank dini** » Fri Jun 27, 2003 4:15 am

quote:Dog, I'm engaging in a conversation here. Just because you posed one thing that you say is a fact does not mean that the topic is not up for debate. The ECUs compensation for engine knocking has been discussed in these forums before. I understand the basics of octane, fuel compression, and premature detonation. The facts as I understand them are, that in a modern car (such as our lovely Vibe), the computer can detect knocking if it occurs, and adjust the air/fuel ratio and/or spark plug timings to compensate for the premature detonation. In this case, since the computer can compensate for the knocking, the driver will not notice any knocking, but will experience a degredation in performance. I am relaying my experience to the group, that since I put 89 octane in my car, it has "felt" better to me. I am asking if other drivers have noticed similar phenomenon, or can comment on my experience. From what I have heard, the 10:1 (or so) compression ratio of the 1zz is pretty high for 87 octane gas.you lost me there but I love 93.

lumpcus · Post by **lumpcus** » Fri Jun 27, 2003 4:26 am

lol.. simple fact gt's need 93 so whatever.

Nervous_Dog · Post by **Nervous_Dog** » Fri Jun 27, 2003 5:36 am

True, the ECU can compensate for engine knocking under normal conditions. Have you ever hit the fuel cut-off at redline? It's quite a shock and isn't good for the engine if done repeatedly. quote:Just because you posted one thing that you say is a fact does not mean that the topic is not up for debate.You're correct, sir. I'm not a mechanic and have no credentials to back up my statement. Now that I've thought about it, I would doubt anybody who just came up and couldn't prove what they were telling me. Sorry if I acted arrogant. Let me restate my stance on this topic:I have researched this topic with mechanics, on the internet, and on other message boards. I was also souping up cars when gas stations still sold leaded gas, but that's a different story. I can't find any conclusiove proof that says your engine will be more powerful with higher octane gas. If that were true, why wouldn't GM market the base Vibe as having 150hp and tell you to use premium? Because they know it isn't true. Do you think I could keep up with Mustangs if I fill the tank on my GT with 110 octane aviation fuel? I don't.I just didn't want you to spend more $$$ then you have to, but the nice thing about America is we can all have our own opinions. You feel the extra octane is worth it, I don't. That's cool with me.

millster · Post by **millster** » Fri Jun 27, 2003 9:17 am

quote: In this case, since the computer can compensate for the knocking, the driver will not notice any knocking, but will experience a degredation in performance. Exactly. It will adjust to keep the engine from knocking, but it will be at the expense of performance. In this case, from low to middle grade, you'll notice a difference. Middle to supreme would be a waste. The compression in the base engine is simply not high enough to warrant top octane.

tau166 · Post by **tau166** » Fri Jun 27, 2003 9:41 am

quote:How is a spark plug designed for a specific octane, exactly?A spark plug provides a spark.I'm not an automotive tech so I can't get into details too much. My info comes from my brother who went to school for this stuff and was a tech for mitsu, lexus, and toyota at various points during the last 12 years. Everytime my dad says something about "treating" his car to some higher octance gas he gets a lecture on this from my brother about wasting money, not burning all the fuel, lower MPG, etc. To attempt to clarify, it's not so much that the spark temp is different, but that the spark plug itself is designed for certain cylinder temperatures. If it's too hot it will cause pre-detonation (bad). Too cold and it won't burn everything up and you get deposits and build up (bad).check http://www.sparkplugs.com/faqmain.asp and click on the link for "How do I find a colder or hotter plug?" and then the link for "heat range" This should help clarify some of it.Like I said before, my .02

shibaman · Post by **shibaman** » Fri Jun 27, 2003 11:12 pm

I had a VW Jetta with a knock sensor and you could tell the difference between 87 and 91 oct. gas. The computer retards the timing with the lower oct. gas. I would think that the Vibe would do the same thing. 10-1 compression is high for 87 oct. gas. I may try 89 oct and see how it feels. I have modified the stock intake box and ran 3" tubing into the bumper for cold air. There is a big improvement in low end especialy when it is real hot with the air on.

MadBill · Post by **MadBill** » Sat Jun 28, 2003 12:27 am

If someone really wants to know what's happening with different fuels, a GM Tech II or aftermarket scan tool can track knock signal and degrees of retard. (Also there is at least one "piggyback" device for ~$150 that just reads degrees of retard via a row of L.E.D.s) If it showed some retard, then more octane would help power, regardless of the factory recommendation for 87 . If it showed none, I'd be enormously sceptical of any claims re power gain from higher octane. Every test I've seen or read has shown that "enough" octane is enough and more is worthless or has negative value.

Jethro · Post by **Jethro** » Sat Jun 28, 2003 1:37 pm

quote:Modern cars will not knock.Really?? Apparently you haven't driven a FORD w/ their Vulcan V6 (most Taurus/Sable except those with the nice 24-valve motor) lately.Having purchased one of those affected cars I can only say I wish you were right.My Sable sits in the garage (losing value almost as quickly as my 401k) a lot as the Vibe is a much better car.

Larry · Post by **Larry** » Wed Jul 02, 2003 8:02 am

http://www.ftc.gov/bcp/conline/pubs/autos/octane.htmThe Low-Down on High Octane GasolineAre you tempted to buy a high octane gasoline for your car because you want to improve its performance? If so, take note: the recommended gasoline for most cars is regular octane. In fact, in most cases, using a higher octane gasoline than your ownerâ€™s manual recommends offers absolutely no benefit. It wonâ€™t make your car perform better, go faster, get better mileage or run cleaner. Your best bet: listen to your ownerâ€™s manual.The only time you might need to switch to a higher octane level is if your car engine knocks when you use the recommended fuel. This happens to a small percentage of cars.Unless your engine is knocking, buying higher octane gasoline is a waste of money, too. Premium gas costs 15 to 20 cents per gallon more than regular. That can add up to $100 or more a year in extra costs. Studies indicate that altogether, drivers may be spending hundreds of millions of dollars each year for higher octane gas than they need.What are octane ratings?Octane ratings measure a gasolineâ€™s ability to resist engine knock, a rattling or pinging sound that results from premature ignition of the compressed fuel-air mixture in one or more cylinders. Most gas stations offer three octane grades: regular (usually 87 octane), mid-grade (usually 89 octane) and premium (usually 92 or 93). The ratings must be posted on bright yellow stickers on each gasoline pump.Whatâ€™s the right octane level for your car?Check your ownerâ€™s manual to determine the right octane level for your car. Regular octane is recommended for most cars. However, some cars with high compression engines, like sports cars and certain luxury cars, need mid-grade or premium gasoline to prevent knock.How can you tell if youâ€™re using the right octane level?Listen to your carâ€™s engine. If it doesnâ€™t knock when you use the recommended octane, youâ€™re using the right grade of gasoline.Will higher octane gasoline clean your engine better?As a rule, high octane gasoline does not outperform regular octane in preventing engine deposits from forming, in removing them, or in cleaning your carâ€™s engine. In fact, the U.S. Environmental Protection Agency requires that all octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against the build-up of harmful levels of engine deposits during the expected life of your car.Should you ever switch to a higher octane gasoline?A few car engines may knock or ping â€” even if you use the recommended octane. If this happens, try switching to the next highest octane grade. In many cases, switching to the mid-grade or premium-grade gasoline will eliminate the knock. If the knocking or pinging continues after one or two fill-ups, you may need a tune-up or some other repair. After that work is done, go back to the lowest octane grade at which your engine runs without knocking.Is knocking harmful?Occasional light knocking or pinging wonâ€™t harm your engine, and doesnâ€™t indicate a need for higher octane. But donâ€™t ignore severe knocking. A heavy or persistent knock can lead to engine damage.Is all "premium" or "regular" gasoline the same?The octane rating of gasoline marked "premium" or "regular" is not consistent across the country. One state may require a minimum octane rating of 92 for all premium gasoline, while another may allow 90 octane to be called premium. To make sure you know what youâ€™re buying, check the octane rating on the yellow sticker on the gas pump instead of relying on the name "premium" or "regular."For More InformationThe FTC works for the consumer to prevent fraudulent, deceptive and unfair business practices in the marketplace and to provide information to help consumers spot, stop and avoid them. To file a complaint or to get free information on consumer issues, visit http://www.ftc.gov or call toll-free, 1-877-FTC-HELP (1-877-382-4357); TTY: 1-866-653-4261. The FTC enters Internet, telemarketing, identity theft and other fraud-related complaints into Consumer Sentinel, a secure, online database available to hundreds of civil and criminal law enforcement agencies in the U.S. and abroad.

esjones · Post by **esjones** » Wed Jul 02, 2003 8:05 am

...and we're supposed to believe the government?

MadBill · Post by **MadBill** » Wed Jul 02, 2003 8:55 am

I would say this information is true for older vehicles lacking knock retard capability. With electronic knock detection/retard systems however there would normally be no audible knock unless the fuel was severely defficient, so the only common effect would be a subtle or maybe not so subtle loss of performance due to the retarded spark timing.

ragingfish · Post by **ragingfish** » Sat Aug 09, 2003 5:44 am

Now here's a question for someone...You say that the spark plugs in the base Vibe are designed for say, 87/89 octane.Supposing I switched to a mid-grade spark plug, and used mid grade gasoline (suppose 90/91), would I see even a mild performance increase, r will the compression ratio of the engine still limit my performance?

MadBill · Post by **MadBill** » Sat Aug 09, 2003 6:26 am

quote:Now here's a question for someone...You say that the spark plugs in the base Vibe are designed for say, 87/89 octane.Supposing I switched to a mid-grade spark plug, and used mid grade gasoline (suppose 90/91), would I see even a mild performance increase, r will the compression ratio of the engine still limit my performance?Err... Don't know who said spark plugs are designed for a particular Octane of fuel but it's not so! The factory selected heat range depends on a dozen or more factors such as cold fouling resistance, compression ratio, cooling system design, air/fuel ratio, pre-ignition resistance, horsepower, type of operation, etc., but not Octane.For example, an endurance race (not drags) engine would likely need a colder plug, as the intense heat of sustained full load could raise the tip of the plug to a temperature that might light off the fuel before the spark fired. On the other hand, the plugs in a vehicle (especially an older carburetted one) used only for low speed, short hop service might foul due to being too cold to burn off deposits unless a hotter plug was used.

ragingfish · Post by **ragingfish** » Sat Aug 09, 2003 6:29 am

So essentially, the only way to get a boost from a mid-grade octane fuel is to get an engine designed for it?

MadBill · Post by **MadBill** » Sat Aug 09, 2003 6:40 am

Pretty much. The only exceptions might be if the manufacturer cut things a bit too close with spark timing and compression, etc., while trying to maintain "regular fuel" compatibility, in which case slight gains might be possible. Also, if carbon deposits or cooling system problems developed, a change to higher octane fuel might "band aid" the problem.

joatmon · Post by **joatmon** » Sat Aug 09, 2003 6:41 am

I found a good write up about octane at http://www.fitchfuelcatalyst.com/techin ... tfuel.html I think for the Vibe, it's not so much that increased octane in a base will give you better performance, more like there are performance improvements possible on the Vibe that will require increased octane. In http://forums.genvibe.com/zerothread?id=5275, Scott said that because of the effective increase of compression produced by the supercharger, a base engine with SC will likely need higher ovctane. Also, there's usually a "performance chip" on ebay that 's basically a resistor to advance your timing, and the advance timing may give you a performance improvement, but will also require use of a higher octane fuel to prevent knocking with the advanced timing.I don't think that just increasing your octane without any other change will have much of an effect on anything except your wallet.

ragingfish · Post by **ragingfish** » Sat Aug 09, 2003 6:48 am

I think your psychotic to buy that chip off ebay.That's just my $0.02 though...

joatmon · Post by **joatmon** » Sat Aug 09, 2003 6:54 am

I wouldn't either, and I wasn't recommending it, it's been talked about here before. http://forums.genvibe.com/zerothread?id=4082 I was just using as an example of a mod that may require increased octane.

ragingfish · Post by **ragingfish** » Sat Aug 09, 2003 7:04 am

I didn't mean that as YOU'RE nuts...just anyone who does has to be outta their mind...

scherry2 · Post by **scherry2** » Sat Aug 09, 2003 8:47 am

just a note. I just got back from a drive from fort wayne indiana to chicago, first trip with the CAI.i filled with PREMIUM GAS and got 35 mpg. without the CAI and regular gas I got 30 mpg so if what you say is true the CAI increased my milage but it was less than what it could have been because premium gas will lower my mpg. also it ran great!!!just my 2 cents. but then the government is right about everything right?

ragingfish · Post by **ragingfish** » Sat Aug 09, 2003 8:54 am

I think someone needs to do an unscientific investigation. Fill a base with regular gas. Do a 30 mile trip, level terrain, constant speed. Fill again. Calculate your MPG rating. Then drive normally. When you hit E (not the 1/4 tank mark) fill again with premium. Drive 75 to 100 miles or so, so you know the regular is out of the tank and you're on premium gas. Then do that same trip, same road, same speed. Fill again (go back to regular if you want). Calculate your MPG. That's the only way I see us getting a somewhat accurate idea if premium hinders performance...I don't have adequate roads out here, so I can't do it.

MadBill · Post by **MadBill** » Sat Aug 09, 2003 9:15 am

quote:I found a good write up about octane at http://www.fitchfuelcatalyst.com/techin ... tfuel.html ...That IS a pretty good write up! Even a nit-picker like me can find only a couple of minor errors:1. Detonation is the spontaneous combustion of the cylinder end gases all right, but the "colliding flame fronts" is a myth. First, since the end gases explode instead of burning, there is no secondary flame front. Second, if there was, it would be like when two grass fires burn until they meet: when that happens, they just...go out!2. IMEP is not "Instantaneous...", it is INDICATED Mean Effective Pressure, or the average value read by a cylinder pressure recording device.3. I reserve judgement on the theory and effectiveness of the Fitch catalyst pending data from a nationally accredited independent laboratory.

ragingfish · Post by **ragingfish** » Sat Aug 09, 2003 9:17 am

I agree. Product is very intriguing. But I'm not going to spend that kinda money, NOR am I gonna drop an unknown device into my fuel tank, until I have some hard-core proof this product is safe, and does what it says it does...

joatmon · Post by **joatmon** » Sat Aug 09, 2003 10:02 am

Mike, the problem with your mileage test is that it involves "filling the tank", which is a subjective task. I can squeeze in more gas after the pump shuts off, and the amount I can top off varies from pump to pump. The scientific way to measure it would be to install some sort of fluid flow meter to measure the actual amount of gas used while travelling a certain distance. Not having one, you could run the test on each grade of fuel over a large enough number of tanks so that the variations in how full the tank is filled average out and become insignificant. Either that or drive the car until it runs out, fill with a gallon of low test, drive till it runs out, then fill with a gallon of high test and drive till it runs out. then use a third gas can to put in enough gas to get back to a gas station.Bill/MikeI was thinking about trying the Fitch catalyst, we were talking about it in the Improving Gas Mileage thread Unfortunately I can't spare the $150 right now. If I do go for it, I'll let you know if it was worth it or not. I'm not a nationally accredited independent laboratory, just a cheap SOB trying to cut fuel costs.

ragingfish · Post by **ragingfish** » Sat Aug 09, 2003 10:10 am

Well, if you don't top off, it would be slightly more accurate...just let the auto shutoff do the work...

joatmon · Post by **joatmon** » Sat Aug 09, 2003 10:21 am

As long as it was the same pump and all the other factors that affect when the pump shuts off are the same each time.

ragingfish · Post by **ragingfish** » Sat Aug 09, 2003 10:24 am

Well, ideally, you'd be on the same stretch of road, so using the same gas station, and perhaps the same pump...

NovaResource · Post by **NovaResource** » Sat Aug 09, 2003 10:52 am

WOW! This thread came back strong while I was gone today. OK, using higher than 87 octane in an unmodified base is just a waste of money. To the same extent, using lower than 91 (except for very short periods of time) in a GT will cause engine performance loss and possible engine damage.Now, if you make changes to the base you may need higher octane. things like turbos, superchargers, nitrous, chips, etc require higher octane because those things create higher cylinder pressures and/or advanced ignition timing.Speaking about chips, the junk on eBay are just that, junk. They really aren't chips anyway, they are resistors and they don't advance timing properly. What they do is fool the engine into thinking the air going into the engine is cooler than it really is so the engine then adds more fuel and could advance the timing slightly. The problem is, the air entering the engine isn't really cooler so the engine runs rich which causes other problems later done the road. Things like a real computer chip do advance timing but without causing the car to run righ. Here is a proper computer upgrade:http://forums.genvibe.com/zerothread?id=411

Bowlsie · Post by **Bowlsie** » Sat Aug 09, 2003 5:18 pm

Just a little helpful advice here. When you are filling up your tank and the pump cuts off STOP. Do not try to squeeze in another .25 or .50 cents in it. What this will cause is a big ses light. What happens is you are spilling extra fuel into the vapor cannister and this will bring on the light. The fuel will evaporate after time but it will stay there until it does. I see it happen all the time. Another thing, if you run your vehicle down to where there is no fuel hitting the sender and go to put some more back in that is a quick way to kill a fuel pump. What happens in this case is the nice cool fuel hitting the already warm pump. Blammo! It's kinda the same principal as say football practice on a 100 degree day and then you hit yourself with a 30 degree chug of Gatorade. Can cause the ol heart to give out. Just throwing some save your money in the long run advice.

goodvibe · Post by **goodvibe** » Sun Aug 10, 2003 9:40 pm

The theory behind the ebay chip is to make the car run slightly rich so that it will advance itself because it's less likely to to trigger the knock sensor and retard the timing. It's not something I would buy and will only cause poor milage, more deposits and premature cat failure if your car is not already lean.

VibeInTx · Post by **VibeInTx** » Sun Aug 10, 2003 10:20 pm

A lot of people in this thread have been blindly saying "anything more thant 87 octance is a waste of money", because that's what the spec sheet says. Sheesh, can't someone else just spend the extra $5 for a tank and try it? I for one think it's very feasable for Toyota/Pontiac to market the specs with regular gas, even if it's less than ideal, considering the economy car market.

ragingfish · Post by **ragingfish** » Sun Aug 10, 2003 10:22 pm

quote:A lot of people in this thread have been blindly saying "anything more thant 87 octance is a waste of money", because that's what the spec sheet says. Sheesh, can't someone else just spend the extra $5 for a tank and try it? We're not stopping anyone from trying. If you followed closely, I posed a challenge a while back to find out if there really is any benefit.If someone wants to buy 93 octane for a car that doesn't require any higher than 89, we're certainly not stopping them from throwing that money away...But we ARE looking out for each other, and trying to help whenever we can.

NovaResource · Post by **NovaResource** » Sun Aug 10, 2003 11:27 pm

quote:A lot of people in this thread have been blindly saying "anything more thant 87 octance is a waste of money", because that's what the spec sheet says. Sheesh, can't someone else just spend the extra $5 for a tank and try it?It's your money, waste it all you want.http://www.caranddriver.com/article.asp ... e_number=1

goodvibe · Post by **goodvibe** » Sun Aug 10, 2003 11:29 pm

Can't help with a fill up. Got a GT but. This one may well be a seat of the pants upgrade. GT's are a bit leaner at low rpms and I suspect your base may be the same. You may be getting very slightly more advance at the low end from the reactive knock sensing ecu. I know no one has ever heard knock on a vibe. The ecu is too fast for that. It probably wouldn't show up on a dyno or 1/4 mi times because the difference is within the margin of error and probably doing more outside of peak power. It may still feel more responsive even at part throttle. Pure speculation as to why you may not be crazy. Some people say they feel the difference between different brands of gas. On the short term the difference can only be octane. Lower octanes have as much energy as higher octanes, they just ignite too quickly. The octane rating is effectively a measure of resistance to knock. After 89 I'm sure there is nothing to be gained. Maybe try a busy station that ussually has fresher 87 or a different brand (everthing has a tolerance) and see if the results are similar. All I'm saying here is that it's worth a try and that if it feels better, it may be so.

VibeInTx · Post by **VibeInTx** » Sun Aug 10, 2003 11:39 pm

If you read the post that started this thread, it was about me using 89 octane in the base.

goodvibe · Post by **goodvibe** » Sun Aug 10, 2003 11:45 pm

That is clearly addressed in my post. I'm writing about a base. It's about why you may be right. I won't use any of the octanes I was referring to in my GT. I use 93. Thought it might help, Oh well. *I just noticed that the previous post may not be directed at me. If so; Never mind.

goodvibe · Post by **goodvibe** » Wed Aug 13, 2003 12:22 am

That you could do that without problems shows how smart these cars are.

disneydj · Post by **disneydj** » Wed Aug 13, 2003 4:05 am

You think it runs good with 93 Octane... saunter up to the table and try 110 Octane... Bad news is it's like $4.50 a gallon... he he he.So who, with a GT, wants to try that? I'll even buy!

slickshoes · Post by **slickshoes** » Wed Aug 13, 2003 4:16 am

i fill up on 89 for my base, i see no probs, there 2 other vibes in the neighborhood i live in a silver gt and silver base, i wanna try to catch the other base owner when hes outside so i can ask what hes fillin up on.

MadBill · Post by **MadBill** » Wed Aug 13, 2003 7:34 am

quote:You think it runs good with 93 Octane... saunter up to the table and try 110 Octane... Bad news is it's like $4.50 a gallon... he he he....!Not me, for sure! I just coughed up $35 to fill my base Vibe with regular this morning!