Mixing Gas

[emiii0]

I was wondering if mixing a lower grade gas and an upper grade one off and on would hurt my car? I know it says premium gas is recommended but the way with gas prices are it's not always possible. Will it hurt my engine to switch back and forth or should I always use the premium grade?

[damronjr]

Just out of curiosity, what are your gas prices over there on the other side? As for mixing, I think it is recommended that you use premium, but I think it would be best to stick with that. I have put higher grade gas in my car and truck, but I'm not sure if it is good to put lower grade gas in a premium car.

[emiii0]

It's not too bad at the moment...$2.02 for the lower grade and $2.22 for the higher stuff....but the way things are going in Iraq I'm sure prices will rise again..P.S. That is a nice looking vibe you got there! I got that same sticker "You just got beat by a wagon" coming in the mail.

[damronjr]

Quote, originally posted by emiii0 »It's not too bad at the moment...$2.02 for the lower grade and $2.22 for the higher stuff....but the way things are going in Iraq I'm sure prices will rise again..Wow, I thought ours were bad! It is at like $1.90 for lower grade here right now (on base, which is usually quite a bit cheaper than out in town). I'm sure you're right on the rising of the prices, though!

[ragingfish]

Read the manual.You bought a GT, you gotta use premium. Using anything lower than the minimum recommended grade can damage your engine in the long term.If you can't afford to put premium in the tank, drive back to the dealer and trade in for a base model.Damage caused to the engine by running the wrong fuel is NOT covered by warranty!

[dsegundo]

Just a tangent to the aside:Say you have 93 octane in a tank (any tank for this reason)then you put in 91 octane in it. Does the octane have anything to do w/ weight or not? would it be a 92 octane gas tank?

[Jahntassa]

You are kidding, right? I think the manual calls for 91 octane. And I would heed it. The reason the GT needs such high octane is because of the compression in the engine. If you use lower octanes (87 89), it can cause knock, which is premature detonation. This can damage the cylinder and the piston head. Not to mention it screws with emissions. You may be able to go to an auto parts store and get some 'octane boost', but I don't know how well that will work..You can run one tank every once in a while as regular on a GT, but it is NOT a good idea. As Mike says, if you screw up something in the engine by using inferior gas, it will not be covered under warranty.As he says, you pay to play. If you can't afford the gas the GT uses, trade it in for an AWD or Base.

[StampedeVibe]

At 20 cents for the difference, even if you use 40 gallons a week, it's just $8 per week more, or $32 per month more (out of a ~$320 gas bill).Just my 2 cents (no pun intended)

[Psychobroker]

Quote, originally posted by damronjr »Wow, I thought ours were bad! It is at like $1.90 for lower grade here right now (on base, which is usually quite a bit cheaper than out in town). I'm sure you're right on the rising of the prices, though! Come to L.A. and you'll find $2.23 for 91 Must we go around this "premium in a GT" block again? Aren't there like 12576355 threads here about it?EDIT: Oh ya: http://forums.genvibe.com/zerothread?id=14504

[DavidPIL]

Hi...Why did you buy a GT in the first place? If you bought it back in 2003 when I did and the gas was $1.60-$1.69 for premium, you were paying 13% more for premium than for regular. (given a $.20 spread)Now at $2.10-$2.19 for premium you're paying only 9-10% more for premium.... It's a bargain now! Basically, back in 2003, you paid $2.00 for 10 gallons more than regular, now you're still only paying $2.00 more for the same 10 gallons. The additional cost is really no more than it was when the gas was $.50 less. It's not such a bad thing.Oh, and to answer your question directly, Most Mid-grades mix the Premium and Regular fuels. This is especially if your gas station has the 1 pump handle for all 3 grades. Already being mixed so you don't have to. (The way to know for sure if the mid-grade is a mix of prem and reg, check to see if the pump itself has 2 or 3 analog gallon counters - Looks like an analog odometer). One suggestion, if you don't think you can afford the Premium, save your change. I almost always end up with more than enough spare change to make up the $2.00 difference. Buy the Premium, don't short-change your engine. (sorry about the pun)Dave

[jake75]

Recently the "Click and Clack" car column addressed this question. They said all modern cars have an anti-knock sensor which adjusts (retards) the timing if you use a lower octane fuel and therefore use of lower octane gas will not harm your engine. However, they also state that this results in less power so your savings per gallon might be at least partly used up by lower mpg. On the other hand, I agree that it makes no sense to pay more for the GT and its added power and then complain about the cost of the fuel requried for GT performance. Would be like having Pam Anderson over and giving her flannel pj's to wear to bed. Around here I think the three levels of fuel are 87. 89 and 93. To get 91 you can blend 33% 87 octane and 67% 93 octane.

[micheles_bad_vibe]

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[Kari]

The minimum octane rating for "premium" gas is higher than the minimum octane rating for regular. Gas you purchase at any price can legally be a higher octane than what is listed on the pump, and sometimes is, but it must be at least what the minimum listed is. It's not really a hard and fast measurement...just a minimum.

[Dave_ca]

http://auto.howstuffworks.com/question90.htm gives an excellent discription of what Octane is. Putting 87 octane into an engine that is running 11.5:1 compression will end up costing you money in the long run. Your engine life will be decresed, your power will be decreased and Fuel economy will also decrease. Please do not live under the illusion that your car can retard its performance to protect your engine in the long term. Knock sensors where designed when the required octane is not available, a temporary fix so you dont ruin your new vehicle from one tank of bad gas. If Fuel economy where/are #1 on your list, it would be a good idea to look into getting a Base model Vibe, or something else that was designed to run on 87 octane.

[DavidPIL]

Hi...I think any milk that we're able to buy at a grocery store is "Premium" considering the USDA has inspections and minimum requirements for quality. Also, taking your analogy further (although I don't think you can really compare fuel to milk) Skim milk - $2.48 a Gallon, 2% milk $2.85 (at my local grocery store). Not sure how that compares really but considering reg gas has less octane and probably less cleaning agents than Premium. Skim milk-less fat than 2%. Although if you compare foods it seems when things are taken out the price goes up. like lower fat/carbs... as in milk, lactose free milk... you get the picture.The title "Premium" is really just a label anyway. Simply means the most additives, highest octane available for street engines. If it was just called "Low/Medium/High Octane Fuel" then maybe you wouldn't have such a beef. The 2zz-GE engine, whether you believe the manufacturers statement that 91+octane is needed, runs better, has more power, and gets better gas mileage than if using less than 91 octane fuels. If you don't want to pay for high octane gas then don't get a GT. If you don't have a GT and you start to notice some acceleration lag or rough idle or it loses some get-up and go, try a tank of "Premium" and see if it's not worth it.DaveP.S. ok, I'm not saying the base Vibe should have Premium in it but sometimes a tank can help regain some oomph in engines that are normally fine with 87 octane.

[jake75]

Quote, originally posted by DavidPIL »Hi.... . . but considering reg gas has less octane and probably less cleaning agents than Premium. If you don't have a GT and you start to notice some acceleration lag or rough idle or it loses some get-up and go, try a tank of "Premium" and see if it's not worth it.DaveP.S. ok, I'm not saying the base Vibe should have Premium in it but sometimes a tank can help regain some oomph in engines that are normally fine with 87 octane.Gasoline marketers like to sell Premium grades as they make a lot more money on them than regular grade. They really never say that their regular grade has fewer cleaing additives. I suspect that for competitive reasons it does not. Also I think there were a couple of FTC false advertising cases that made that point as well.A lower level of cleaning agents would be the only reason an occasional tank of higher octane might be of any help to an engine designed for 87 octane fuel. As I don't believe that the additive package differs, I am not going to spend the extra 20 cents a gallon for premium even occasionally.I have heard a theory that as the cylinders get carboned up that the pressure increases and it is the same as having a high compression engine needing hihge roctane fuel. That also does not make much sense to me. A good additive package will prevent that. I do only buy brand name gasoline - mostly Shell and occasionally BP Amoco. With gas cards that give me a 3-5% rebate the Shell and BP brands are no more expensive than off brands. P.S. I am a dairy regulatory "expert". Not going to go in to the quality issues with milk except to say that it is not the USDA but rather the state milk agencies that monitor the quality and safety issues. There is a "minimum" that some milks meet, while others are of higher quality. Pricing is a separate issue and in large part depends on the market price for milkfat and nonfat milk. Currently milkfat is relatively high priced compared to nonfat milk solids so 2% and whole milk ought to be priced higher than skim (nonfat milk) but often the supermarket charges the same for all. Likewise Vanilla ice cream is a lot cheaper to make the Butter Pecan Ice Cream but all ice cream flavors in a line generally retail at the same price.

[DavidPIL]

Hi Jake...sorry about that but my point, and what you mentioned as well, is that there are different grades, expectations and requirements. I'm not sure but I think I've seen some dairy producers label their products "Premium" an, I'm sure, a higher cost. I was kinda jokingly trying to compare fuel to milk, as to whom I was replying. I think Shell markets V-Power as a fuel with 5x the required cleaning agents and 50% more than their old "Premium". Shell used to suggest a tank of their "Premium" to help clean deposits. http://www.shell.com/home/Fram....htmlAmoco used to advertize it's "Ultimate" as a clear fuel but I'm not sure if they still do since it's changed most everywhere to BP-Amoco now.(Just haven't seen the same ads) I don't believe their mid or low grades was clear nor did/do they have the same cleaning agents. http://subsites.bp.com/ultimate/us/about/why.aspThese sites do seem to mostly compare their "Premium" to other brand's but there is specific mention of these 2 new "Premium" formulas having more cleaning agents than their previous high octane version.The point is still, the GT requires a higher octane to peak performance. Lower than required octane will eventually do damage. Can the original poster mix High and Low grades, sure but it's not recommended to use fuel under 91 octane consecutively in the tank and since most pumps mix the High and Low already to make their Mid grade, then why do the mixing himself?Dave

[ColonelPanic]

I can't seem to find the post... But I swear that I remember reading from somewhere that they have some insanely high octane ratings in Nevada, no? Something like 100, maybe more? If you fill up with that really high octane stuff from darn near empty, could one possbily fill the tank back up with the next lowest grade, which if I remember, was 89 IF you have 3/4 or 1/2 tank left of the super high stuff? I don't know squat about this schtuff, figured I'd throw it out there, fuel for the octane fire. Yes I know that's probably been discussed. One thing I am curious about... In regards to the high performance car needing high performance fuel, I'd like to know how well the dealers are notifying their customers about this necessity. Is the average salesman even aware that the base and AWD Vibe needs 87, yet the GT needs 91? I know I would be bringing that up to my potential customers. But seeing how we often know more about the cars, than they, I wonder... Why I mention that is the dealer's lack of doing just that when the folks' bought their '04 Impala SS over the summer. (I was along for the ride for that transaction.) Being a car with a friggin' supercharger, I suspected that it would. Dad did as well, but the salesman didn't say squat about it. The Impala's base engine and the 3800 have only the usual 87 requirements, add the blower onto the 3800 and that requirement jumps to 91. But the salesman was too full of himself yacking about the steenkin' OnStar and XM that he seemed to have forgotten to mention the car's minimum octane requirement. In the end, Dad went to fill up the Impala for the first time, and saw the 'Premium fuel required' on the fuel door. Of course by then, we had already confirmed that by reading the owner's manual. But still, it would have been nice if the guy would have said up front that it needed 91 octane. Not really a big issue for them, that car hasn't even broken 3K miles yet and they've owned it since June. But this wouldn't be good for someone who does a lot of driving, wasn't a car person so they wouldn't know about things like this, and the dealer never bothered to tell them. I dunno... Too bad they don't have writing somewhere near the fuel gauges that GM always used to have "Premium unleaded fuel required" when the octane necessary was above the usual 87.End thread hijack... Just something that popped in my head while I was thinking about this.

[jake75]

Quote, originally posted by DavidPIL »Hi Jake...sorry about that but my point, and what you mentioned as well, is that there are different grades, expectations and requirements. I'm not sure but I think I've seen some dairy producers label their products "Premium" an, I'm sure, a higher cost. I was kinda jokingly trying to compare fuel to milk, as to whom I was replying. I think Shell markets V-Power as a fuel with 5x the required cleaning agents and 50% more than their old "Premium". Shell used to suggest a tank of their "Premium" to help clean deposits. http://www.shell.com/home/Fram....htmlAmoco used to advertize it's "Ultimate" as a clear fuel but I'm not sure if they still do since it's changed most everywhere to BP-Amoco now.(Just haven't seen the same ads) I don't believe their mid or low grades was clear nor did/do they have the same cleaning agents. http://subsites.bp.com/ultimate/us/about/why.aspThese sites do seem to mostly compare their "Premium" to other brand's but there is specific mention of these 2 new "Premium" formulas having more cleaning agents than their previous high octane version.The point is still, the GT requires a higher octane to peak performance. Lower than required octane will eventually do damage. Can the original poster mix High and Low grades, sure but it's not recommended to use fuel under 91 octane consecutively in the tank and since most pumps mix the High and Low already to make their Mid grade, then why do the mixing himself?DaveKnowledge is power and unfortunately the gasoline companies keep us in the dark and dont' tell us the whole truth so we can make rational economic decisions. They have convinced me to stick with the major brands and I use only Shell or BP Amoco. I'd like to ask the gasoline marketers point blank if the cleaning ability of their regular gasoline is less than their premium. I suspect not but I don't know. The Shell study showing the difference on the valves says "The image shows Intake Valves after a 5,000 mile Shell test comparing Shell V-Power to a discount brand premium gasoline." Seems to be a waste to force someone to buy a higher octance than necessary just to get the higher level of cleanign agents. I am sure not an expert on gasoline - don't even know what they do to change the octane rating. Is it an additive or a slightly diffeerent refining method. As to "why do the miixing yourself, here it would save a lkittle money. Typically 89 octane is 10 cents more than 87, and 93 10 cents more than 89. A 50/50 mix gives you 90 octance for the same money you'd pay for 89. Would not be worth the bother to me but might be to the real penny pinchers. P.S. The "Premium" milk might be hype or it might be referring to milk with added nonfat milk solids which helps give reduced fat, lowfat and skim milk a taste more like whole milk. [Milk processors in California are required to add nonfat milk solids to such milks but that is largely an economic issue - benefits the dairy farmers.]

[Psychobroker]

Quote, originally posted by micheles_bad_vibe »i'm sorry, but i do not believe in "premium gas"i think it's all a load of crap, trying to convince you that "more expensive is more better" if they sold "premium" milk at the store, you really think it'd be any different that regular milk?? it's all about the illusion of choice, thats how you keep people happyyou make them think they have a choice on how much they're willing to get scr*wed for at the pumpWow, you must be an expert

[jake75]

I didn't think Michelle was claiming to be an expert - just expressing her opinion (skepticism?) that the oil companies attempts to sell us super premium at a 20 cents per gallon upcharge was based on claims that were somewhat less than the truth, the whole truth and nothing but the truth. This thread has caused me to do some thinking. My thought is that if one were in the long term habit of buying generic gas that had the minimum level of detergents then it might be helpful to use Shell (or BP) Super Premium for 1,500 miles to undue the damage caused by that marginal gasoline. On the other hand, if one has regularly used a good quality (Shell, BP Etc.) regular 87 octane gasoline perhaps no clean up is necessary. Is there anyone on this board who actually has "knowledge" of what is going on? Perhaps an oil company chemist etc.

[goodvibe]

Premium does have more cleaning agents and even it could generally use more. I totally agree with using the correct grade. That also means not to use premium in a base. Your fuel system may stay a bit cleaner but your cylinders will carbon up faster. I suppose if you have 93 octane available, you could mix it at 2-1 with 87 and be fine at 91. A 1-1 mix would be 90 and that may still be OK but you can't be sure. Using a tank or 2 and checking your mileage may be a worthwhile way to find out.

[NascarXprt]

the gas down here is $1.76 - 1.86 unleaded and 1.96- 2.06 super

[Kari]

It was $1.99 here for regular when I filled mine up Thursday.

[B18B]

Quote, originally posted by Jahntassa »The reason the GT needs such high octane is because of the compression in the engine. If you use lower octanes (87 89), it can cause knock, which is premature detonation. This can damage the cylinder and the piston head. Not to mention it screws with emissions. I think Jahntassa sums up the GT's requirement for premium fuel quite nicely.The difference between premium fuel and regular fuel is usually based on the octane level in the fuel. The difference between 91 octane fuel and 87 octane is the ratio of octane:heptane in the gasoline itself; premium fuel having the higher ratio of octane. Octane is a well behaved hydrocarbon which is not as prone as to prematurely igniting under compression as heptane is. Premature ignition of the fuel leads to the problems which Jahntassa mentioned earlier. So what you're essentially paying for when purchasing premium fuel is "better behaved gasoline" and is a necessity for high compression engines such as the GTs.This is also why some people experience increased fuel economy when they use premium fuel in a car which only requires regular fuel. The savings in mpg or L/100km are the result of more efficient combustion, and hence reduced fuel consumption.Gasoline up here in Toronto is currently 93.9 cents/L. It is also interesting to note that aside from the higher ratio of octane in their premium fuel, Petro Canada has also marketed its premium fuel as having more detergents in them (3x more, infact) than their regular gasoline.

[goodvibe]

Premium in a vehicle that calls for regular would actually give you less efficient combustion. The octane level measures the resisitance to combustion and premium will not give as much power or mileage in a vehicle that is operating correctly on regular. It will also leave more cylinder/valve deposits from less complete combustion. Use the right grade and a cleaner now and then. I use a maintainence dose of Fuel Power (2oz. per 10 gal.) in every tank.

[joatmon]

I bought a base because of both the better mpg rating and because the GT requires premium fuel, and also taking into consideration that the extra power of the GT wasn't worth the cost. (purchase, insurance, and fuel)a base 5 speed is rated at 36 mpg highway. It would take 2778 gallons to go 100K miles, at $1.80/gallon it would cost $5000. A GT is rated at 32 mpg highway. it would take 3125 gallons to go 100K miles, at $2.00/gallon it would cost $6250. This means that over 100K miles, the GT might cost an extra $1250 for fuel. That works out to be 1.25¢ per mile more for the GT than for the base. At the "standard" annual mileage of 12,000 miles, that's about $150 more per year ($12.50 more per month) to fuel the GT. (if gas goes to $2.80/regular $3.00/premium, then the difference goes up to ~1600 more for the GT, mostly due to lower mpg rating)Anyone considering buying a Vibe should make the decision of whether the extra power in the GT is worth the exra costs. Most of the GT owners here would say that it is. Hitting lift has got to hurt mpg's, so if you want to save some gas money in your GT, then drive it for efficiency, hold that extra power in reserve for only when you really need it. If fuel costs don't really matter, then hit lift every chance you get. The difference in the fuel cost from how you drive can easily be more money than the difference between using regular and premium.

[GMJAP]

Low grade = for most carsMid-grade = marketing crapPremium = for engines that require it due to design for performance needs. Not using can cause knocking and damage the engine, as has been said.

[DavidPIL]

Hi Joatman and all....Yeah, I had to consider the fuel costs considerably before getting my GT. But before I had the Vibe, I had a Truck that barely made 27 mpg, knocked horribly with 87 octane (used 89 octane but got it at only $.02 more so it was worth it). One thing people also have to figure in your numbers is some of us are lucky enough to have gas stations where the difference between each grade is only $.09 so the difference is dropped by 10%. Also, for me, I can drive 8 miles to 1 of 3 truck stops (2 Marathon and 1 Philips)where there's on;y a $.12 overall difference between regular and premium, thus lowering the difference even more.But anyway, good numbers to chew on though. What I'm seeing in your numbers is a 25% increase in fuel costs for a 38.46% increase in HP. Not too bad really... for me, worth paying the extra $$.$$'s at da pumpDave

[joatmon]

if the premium is $2.00 and regular is $1.90, then it's about $1000 difference over the 100K miles, a penny a mile.However, if you pay the 25% to get the 38.46 % (30.77% 0n 2005s) more power and run around in lift all the time your mpgs are gonna drop to about 20, in which case your cost for gas for 100K miles is going to jump up to $10,000, which means that you'd be paying double for about a thrid more power

[micheles_bad_vibe]

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[Psychobroker]

Sorry, but my 6-speed and LIFT are well worth an extra $150 a year in fuel, which I think is actually a bargain if that's what it works out to.