What octane fuel ?

[2 E L O]

Run as low of an octane as your compression lets you. If you run higher octane than necessary you will get worse gas mileage than if you ran the correct octane.

 

[cam3439]

Well my 5.3L got its best gas mileage with regular 89 and not at 87 or 93. Before the 93 tune I was able to get 20-21 mpg on my '02 Z71 Tahoe on the highway at 70-75 mph.

 

[Grocery Getter]

No haven't head about this, but E85 ruins your engine and you get horrible gas mileage with it. As for the octane, I would at least run 89 (if you're rated at 87). I use to run 89 on my '02 5.3L until I got it tuned for 93. With a grade higher than recommended you should be able to prevent any detonation/pre-ignition. This is what EAGLE is experiencing. It's not that much more expensive and will be safer for your engine. And don't use those octane boosters as they ruin your O2 sensors and your cats.

E85 does not ruin your engine unless it is not set up to run it. That is an ignorant statement. The reason you get less mileage from E85 is it takes more to do the same thing as regular gas. On average E85 is 25% less efficient than conventional gasoline but it is 105 octane so you are getting WAY more power. Now, it is 25% less efficient but substantially cheaper, especially in the midwest, than premium gasoline(91/93 octane). If you do the math generally it's a wash cost wise or you save a few bucks if you live in the midwest and get a lot more power out of your engine if it is tuned for 93+ as mine is. I can tell you from experience when I'm running E85 it's like an extra cylinder which is another reason your milage goes to crap....because it's hard not to drive like a maniac when you get so much more umph out of the pedal. E85 is a great fuel, I don't think it is much "greener" or cleaner but it does cut down our dependance on foreign oil and the corn is made in the USA. If you have a flex fuel engine I highly recommend giving it a shot. I wish it was more readily available here in AZ. It really gets on my nerves when people say it ruins your engine and buy into all the other propaganda put out there by the oil companies.... have you had first hand experience of E85 ruining a flex fuel vehicle? In brazil they run 100% ethanol and all gas stations have to carry it and all cars have to be flex fuel, the only difference is that they use a sugar based ethanol and we make ours from corn. Are you telling me that all the engines in Brazil have been ruined since the late 70's when they started mandating flex fuel cars and ethanol?

 

[cam3439]

Yes, but that's only certain parts of your setup. I'm talking about the aluminum. Of course vehicles have been setup to WITHSTAND the ethanol fuels, but that doesn't change the fact that it still eats the top end of the motor (aluminum heads). The E85 doesn't have a correct octane rating of 105, it's more around the ratings of 96 or so. And yes it does lower our dependence on foreign oil (I'm all for it), but when the E85 first came out it might of been worth getting. Now the dang E85 is pretty much just as expensive as 87 where I'm from and the NBS tahoes/yukons/etc. get horrible gas mileage with it. And if on average its 25% less efficient then why isn't it 25% cheaper. I know corn, etc. might of become more expensive, but I thought that this was suppose to be our cheaper alternative and not a more expensive one. The reason E85 isn't as efficient is because our engines cannot use that type of fuel to its potential. They ran that fuel in the C6R at the Le Mans before and it did great, but that engine was setup specifically for it, whereas ours aren't. They are only setup to WITHSTAND it, and to run it. So this was not some ignorant statement. I have chosen not to run it regularly, and for a reason. It really gets on my nerves when people say it doesn't ruin your engine and buy into all the other propaganda put out there by the government....haha.

 

[rich5368]

Only difference is about $2.50 less in your wallet. However you'll hear lots of arguements saying that it burns cleaner and less pinging and produces more power.

I actually read a study and damn I wish I could remember where that the lower octane actually gives you more power. I don't remember why or how but that was the jist of it lol

 

[Eagle]

well it burns FASTER.

slow burning fuel lets you run more timing and higher compression, which is more power.

 

[rich5368]

Makes sense but the stock PCM is only going to let it go so far. It's not going to say hey I've got premium lets go crazy. I can see the benefit if you're tuned and have work done but on a stock motor with no tune isn't it just a waste of money?

 

[vwbeaner]

These motors stock are not high compression motors and do not need high octane (93) fuel. If you use 93 and the motor does not need it your motor will not burn the fuel correctly. Stick with 87.