ecko51

What is the proper way to go up or down in octane as far as fueling and when to change the tune?


Thanks, Mike

don_w

Rule of thumb... always make sure the octane of the fuel equals or exceeds the octane required for the tune. For example, 91 octane fuel is OK with an 87 tune, but not the other way around.

RedDragon777

and make sure to run atleast 2 full tanks of the new octane before you change to the new tune or you will have problems....best bet is to keep useing 93 octane even if you are running an 87 octane cause you might want to switch one day and you will still have to run the new octane for a while if you keep useing the mid grade or low grade

ecko51

Why 2 tanks? I have heard run the new octane down half a tank than re-fiil but never 2 tanks>

Thanks, Mike

Error404

when you mix 1/2 a tank of 87 with 1/2 a tank of 93 (or 91) you won't end up with full octane rating, you'll end up with 88-89 rating or so. Then the next time you fill up with 91 or 93, you'll be that much closer to your full desired octane rating. If you wait and do your mixing until you have a very low tank, this would be a much better idea than doing it at 1/2 tank. Do that twice (on a very low tank) and you should be good


Think of it like mixing a glass of properly mixed coolaid with a glass of pure water. if you do 1/2 and 1/2, it's going to be weak!


I suppose you could put 1/2 a tank of 104, then add some sort of octane booster, but I still wouldn't trust that your octane has leveled out to what you need it to be.

FireFighterHill

Ive just run nothing but 93 since the day I picked my mustang up from the dealer. And only from name brand stations. And if the station looks old or run down I wont buy gas there, who knows whats gotten into there underground storage tanks. And every 3,000 miles I run fuel system cleaner through my system.

dustindu4

That's pretty stupid if you don't have a 93 tune loaded in

FireFighterHill

Well if you took the time to read my SIG youd see I have a C&L CAI with a 93 octane tune. I had the CAI and tuner before I even picked my Mustang up from the dealer.

scramblr

What kind of problems? I just make sure I get to 1/8 of a tank or lower. If I'm going down to an 87, I change the tune first. Up to 93 I fill up first then change the tune. Never disconnected the battery and never had any problems. Are you talking about something long term?

FireFighterHill

Well you could get a knock from pre-detonation especially if its hot out and your in traffic, because of the changes the tune makes.

dzzzz

That's pretty stupid not to read his stupid sig and call him stupid. Where's the love? WHERE"S THE LOVE??

blk05stang

If I'm going from my 87 tune up to the 93 I wait until it says 0 miles to empty and drive to the gas station. There's still around a gallon of 87 gas left in the tank but I haven't had any problems doing this.

mustangspeeder

I ran my car down to 0 miles to empty, and then the car still went 10 more miles to the gas station when I filled up with 91....loaded the tune the next day and had zero problems.

Galaxie

I agree with what was posted above,

as for going 2 tanks to get all the lower octane fuel out of the system, I don't think its that important as long as you don't do a lot of WOT runs

don_w

What a stupid thing to say...