I just got myself a 95 z28 after a long time of looking, it says unleaded gas only, is there a preference you guys have or use, or just go with the regulat 89 or 87

 

you should run premium, your engine is setup to run it and youll actually get better fuel economy. the extra 4-5$ per tank will actually become a gain when you factor in the extra miles.

ive tested fuel econ with my bike, regular vs premium. regular would get me 175-185 miles (4.2 gallon tank) premium was getting me 195-205 miles.

 

93 octane ($4.05 where I live) is the only thing I put in my car any more. Occasionally I'll run 91, but 89 would be the lowest I'd go in any car. But like BC said, the extra bit of money pays off in the end.

 

I run 91 in mine, mostly because theres nowhere around here to get 93. Also, I generally only get gas at stations that are 0% ethanol. Not all places have pure gas available, but older cars definitely respond better to it than they do the diluted ethanol mix.

 

thanks guys. Do you think theres any truth in that once you use a higher grade gas its bad to go back to regulat, that it can harm the engine?

 

I don't think there is any truth to that. Higher octane results in slower burning, which helps slow ignition and prevent pre-detonation (ignition before the spark plug fires).

An engine that will advance the ignition timing and retard it when it detects knock (like the LT1 does) will benefit from the slower burning, higher octane fuel.

An engine that doesn't adjust to the higher octane at all will generally see no benefit at all. Going to higher octane and back shouldn't matter at all.

I recall in the owners manual of my old '99 Durango 5.2L, it warned against using higher octane, saying the risk of damage was there. I don't know that I believe that.

I own a 5.7L Tahoe and a 4.7L Jeep, I'll run regular in them. I run premium in the '94 Z28 LT1 I have.

I can flash the 4.7L Jeep to run on premium and gain a few HP, I'm guessing the flash will advance the timing.

 

Usually the only time you need higher octane fuel is when your engine is running a high compression (in our case 10.4:1). Take a minivan for example. They aren't made for performance so usually have a low compression allowing them to run perfect on 87 or 89 fuel. Anything more is just overkill and a waste of money because the van isn't squeezing all of the power from the fuel.


Also, do not be swayed into "octane boosters" as others have had. They do not work as great as people will make you out to believe. It takes 10 points to raise your fuel 1 octane level and most "octane boosters" can not do this. There are a few (Lucas is one) that will raise your octane but again, by only one point. So if you buy 87 fuel and use a octane booster that actually works, congrats, you raised your octane to 88 for about $12 when with the same amount of money you could have just bought 93 and called it a day.

Run 93 if you can, 91 or 92 if your area doesn't have 93.

 

All i run is premium gas in my lt1. With the previous posters the premium will make the engine run better and will get better mileage. It does suck on the price especially here in ct depending on area the price of premium could be $4.05-$5.00 per gallon.

 

Best bet is to look in your owner's manual and use whatever it says to use in there. In the case of our V8 Camaros, 91 is good. I use 94 in my IROC, but that is because it's not exactly stock.

Using a higher octane than necessary is just a waste of money, as it doesn't really do anything. Using a lower octane than necessary risks causing engine damage.

The reason is because octane is a measure of the fuel's resistance to ignition- a lower number such as 87, is easier to burn and thus high compression engines will have trouble with it, as it will ignite too soon, causing knock.

 

The owners manual in my car states 93 is "recommended for increased performance", but nothing lower than 87 (where could you get less) should be used. Says "decreased accelleration" may result from lower octane gas. Not doubting the pre-detonantion statements made, because I completely agree, but I find it funny that my owners manual states nothing about damage to the engine from running 87.