Is Premium fuel really necessary on the GT and Matrix XRS ?

[kentb31]

Hi,There is probably another thread on this subject, but couldn't find it...On the Vibe GT (or Matrix XRS for that matter), is premiumfuel a necessity ? What's the worst that could happen if I used regular octanegas ?

[Raven]

Yes it is necessary although expensive. The extra octane is necessary to prevent detonation (pinging) which is potentially damaging. The odd tank of regular may be OK if premium is not available but not on a regular basis. My brother lives in Bathurst, say hello for me.

[joatmon]

running less than specified in the owners manual could cause loss of perrformance/economy due to automatic timing shift, knocking, premature engine wear or damagea couple of previous therads on it are:http://forums.genvibe.com/zerothread?id ... ad?id=2632

[robdog]

91 or higher. High compression engines on top of variable valve timing almost always use premium.

[jake75]

As octanes are usually 87 - 89 - 93 you can save a wee bit of $$$ by filling 33% with 87 and 67% with 93 to get to 91.

[robdog]

why not just use 93 and not cheap out on your high performace engine. that is the question.

[msuphil]

Can the engine even take advantage of anything above 91?Does it advance the timing to take advantage of it?Should we be using 94? Or Racing fuel?

[MadBill]

Quote, originally posted by Sunny »... My brother lives in Bathurst, say hello for me. What a coincidence! So does mine!

[Stang2Vibe]

Quote, originally posted by msuphil »Can the engine even take advantage of anything above 91?Yes. I have seen dyno charts that have shown an increase in power production when the octane rating of the fuel is increased.Quote, originally posted by msuphil »Does it advance the timing to take advantage of it?Yes. The network of sensors will manage the engine timing (within a preset range) to make the optimum use of the fuel in relation to the throttle demand input.Quote, originally posted by msuphil »Should we be using 94? Or Racing fuel?Using 94 octane rated fuel will cause no damage, but will probably not provide much more benefit than using 93. Considering that 93 is going to do about the same thing as 94 but at a lower cost, I would suggest using the 93.Racing fuel is usually leaded (check the labels at the pump). At a few of my local Sunoco stations you can get 110 octane racing fuel, but it contains lead. Using leaded gasoline in your Vibe will ruin your catalytic convertor and probably void parts of your warranty.

[Stang2Vibe]

Quote, originally posted by joatmon »running less than specified in the owners manual could cause loss of perrformance/economy due to automatic timing shift, knocking, premature engine wear or damagejoat is right on this. I have found out that running less than specified octane fuel in these engines could potentially cause major damage. Lower octane fuels are less stabile under pressure and could therefore detonate in the cylinder as the piston compresses the fuel-air mixture before the spark is made that is supposed to ignite the fuel (also called "predetonation" or "dieseling"). Predetonation in a high-compression, high-revving engine can cause the breakage of critical engine parts, which would basically destroy your engine. As said before, it should be ok to use regular fuel in these engines temporarily if the proper fuel is not available, but the engine should not be run hard (or daily) on regular fuel.

[DavidPIL]

Ya know, around here you can find many varieties of octanes... Some stations only have 2 storage tanks, 1 with 87, the other with 91 then blend the 2 for mid-grade 89. Some have 3 separate tanks. Most use 10% Ethanol to boost octane some don't... Found a truck stop near me which had 87/89/93 without Ethanol. Next to that station (Marathon) is a Philips station with 89 as it's low, 91 as it's mid and 94 as it's "premium", I think a cit-go near me has the 94 octane Premium as well though I wouldn't go there. I filled up with the 94 a week ago and I swear I felt a loss of performance. Noticable loss, felt like the engine was working much harder to accelerate. Switched back to the Marathon 93 oct and it's returning to normal.I would have to say that with the variety of fuel octanes I've seen locally, "premium" isn't necessary but at least 91 octane is. And I would suggest to shop around. Try a station's fuel and see if you notice a difference. Through my shopping around I've found a 93 octane which is usually only $.12 more than regular. If you're lucky, you can find this too. Dave

[Stang2Vibe]

Yes, it is recommended that we use a minimum of 91 octane in the GT/XRS. I agree that you can get different results with fuel from different stations. Near me, its almost all 87/89/93, so I get the 93. Sunoco stations have 87/89/93/94 usually, and the 93 is about 10 cents more than 87. But to make the jump from 93 to 94 is usually 4 to 5 cents extra per gallon, so to me the 93 makes the most sense. So you do have to check around to see what's in your area.

[MJN2]

Don't know about the lower MPG, Salsa. I get 28-29mpg pretty consistently driving to and from work (Mixed highway/city).Besides, the last car I had that was "premium only" got about 18mpg on a good day, so I'm not going to complain lol

[Jahntassa]

Dammit..something has GOT to be wrong with mine... I've been consistently getting 22 MPG (mostly City)It's higher than the 17 my Probe got, so i'm not totally complaining..but still..And yeah, the manufacturer reccomends certain fules for a reason. It's already been described here..so I won't restate the obvious

[robdog]

mine gets 22-24 mpg, even on the highway, and i don't have a very heavy foot. I usually get 290-310 mpg per tank. mostly highwaysuberban.

[DopeVibeGT]

Yes.

[dsegundo]

I always wondered what would happen if you mix two different octanes of gasoline....what it be like oil and water? Which one would be "heavier"? Does the mix of octanes really work?

[millster]

Quote, originally posted by Jahntassa »Dammit..something has GOT to be wrong with mine... I've been consistently getting 22 MPG (mostly City)Me too. I don't drive mine all that hard either. I'm not sure what would cause the difference. I get about the same on the highway that I get around town as well.

[DavidPIL]

Do you drive with the defroster on? I read somewhere where people didn't realize the compressor kicked in when they had it set to either of the 2 defroster settings. Although I didn't notice a major loss in MPG on the highway with the AC or defrost on, it's very noticable when stopping and starting more. Maybe? Although my MPG did drop with the colder temps (23-25 mpg down from 30-32), When I stuck with the no ethanol added fuel, my mpg came back up to the 27-29 range in cold weather. I don't usually run the defrost though.I didn't notice if you have one but could a CAI cause a problem with cold car? I know the engine likes cold air but it might take the engine longer to warm up causing a lower mpg. I know that when I didn't plug in my engine block heater and it was below 30 or so, the Vibe took some time to warm-up. Just another thought...I think several posts have other possibilities for bad fuel economy, this is just another thing or 2 to consider. Dave

[millster]

No, I leave the defroster off unless I need it. I do have the Injen CAI. That could well be a part of the problem, as could the snow tires on (currently) dry pavement. I hadn't started paying attention to my mileage until recently when available money became more of a concern (high fuel prices and the addition of a house payment).

[DavidPIL]

silver, But you have to realize that your truck isn't expected to get such great gas mileage. Most base Vibe owners bought it for it's excellent fuel economy. I bought my GT because of the better mileage and more seating copacity than my old truck. I expected to get no better than 17-19 mpg in the Winter with it, less if I ran defrost. I got 26-27 in the Summer, less if I ran AC. If my mpg dropped much lower than whatI expected, I would be a bit concerned but wait a fill-up or 2, maybe boost the octane for a fill-up then hope it improved. If it didn't, I would be concerned or worried. These people with less than 20 mpg for the GT should be concerned, unless they're gunning it all the time or running AC/Defrost 24/7. I don't think it's funny, I think it's worrysome especially if that starts to happen to me. Sure would hate to be pumping $2.00+ a gallon for less MPG than I got with my old truck for which I traded in to get better mpg. And given the fact that things I read on here seem to happen to my Vibe shortly after I read em, I'm really worried now. Does that happen to anyone else? Things going fine then read something on GenVibe then your Vibe starts to do it too? hmmmDave

[Jahntassa]

No CAI for me, and I unplugged the wire behind the AC controls that let the compressor run WITHOUT me hitting a button. Always leave the selector on vent/floor, anyway.I'm guessing it'll go up with warmer weather. I'm concerned, but not enough to go crazy about it. My previous car got 17/26 (though it was more like 20/30 once I got the calipers replaced for the third time). It's still an improvement, so i'm not paniced. It's just weird to see all the other GT owners saying they're getting 25+ MPG, and i'm stuck on the lower end of the spectrum. I'm just concerned that there's something wrong, and i'm not sure what. If the mileage goes up with weather, then i'll just know, the car doesn't like cold weather! No biggie..I'm not complaining, really...just that I only had the car for three months in warm weather, and was driving a LOT of highway. I'll see as time goes on if it goes up. But, it's better to ask around and see if there isn't some issue lurking that can be dealt with now..

[rasermon]

Quote, originally posted by Salsa! » no way with the GT.... Come on... Sorry to bust your bubble Salsa, but it did happen. I still average about 35-40 (highway) mpg. http://forums.genvibe.com/zerothread?id=5705

[AKLGT]

ya, no kidding! last winter i spent $300-400/month in gas alone! that was getting 13-14 mpg in my tundra. this winter i pay about $100-120/mo for gas and my last tank was 314.4 miles and 12.283 gal=25.596 mpg. not too bad for having heat and defroster on at all times, plus driving much much slower in bumper traffick due to rubber necking and slow driving conditions both city and hwy.

[VibeInLA]

What about for the 2005 Pontiac Vibe (base model)?
I bought it second hand with about 125K on it and I would not surprised if the previous owner only tanked 87
I have been using 89 for about 10 k now (driving around in SoCal) but I'm wondering if I'm wasting money not just using 87

Whats the advice and experiences?

[lannvouivre]

Use 87. Higher octane ratings signify the ability of the fuel to resist prematurely detonating under high compression. The GT 2ZZ motor has I think a compression ratio of 12.0:1 or so, so it needs higher octane to prevent pinging. The 1ZZ uses 10.0:1 compression pistons and so does not need higher octane because the gas is not subjected to as much pressure.

That's all there is to it. Higher octane will not give you any better performance in a stock 1ZZ motor, so just go with the cheaper, lower octane gas. The ECU probably isn't even sophisticated enough to see and use the difference in octane anyway.

[Salsa Guy]

Yes 91 Octane or better is needed for the GT/XRS 2zz-ge engine.

On the 1zz Base/XR it's been my experience that 91 Octane does help the performance and the MPG. Seen maybe .5 seconds quicker and 2-4 more MPG. However I'm not sure the cost is worth it. These ECUs have knock sensors and it will advance the timing as long the knock sensor is "happy". The more Octane more advance of the timing equals more power. This has been my somewhat scientific results.

[circuitsmith]

I found that in hot weather (90+F) my 1zz is a little peppier with 89 vs 87, but no MPG increase.