SilverGTV8

I'm from New England. [&:]

Blue70

What kinda Mustang do you have, you might want to double check the numer?????
My 03 manual says 87 Octane unless it's a Mach 1, for them it's 91 octane, I don't know what the heck would require 93!!

94Cbra and SilverGTV8 are correct, running too high of an octane can cost you horsepower.

Chopper

THe DOHC engines have knock sensors,the SOHC engines do not.If your engine can't run 87 octane and the owners manual calls for it,you have probably built up deposits inside the combustion chamber that is actually raising the compression.These deposits can also cause hot spots(glowing embers) that cause pre-ignition.This is not the same as detonation but will have the same disasterous results. In the olden days we used to spray water into the carburetors to break this stuff up and it would blow out the exhaust.Now,you will have to chemically clean the combustion chambers.Running higher octane than recommended,oil bypassing the rings,leaking valve seals,and stop and go driving is what causes these deposits in the first place.A long trip,two hours or more,on an interstate will help burn some of these out also.Use the lowest octane the engine will tolerate cruising at road speed.

Dan04COBRA

Same thing here, I tried a bunch of times to run 87 and 89 and my car pinged so bad it made me nervous to drive it. When it's really cool out I can get away on 89, once it gets hot and humid I have to run higher octane or it'll sound like change banging in a can.

Soaring

Well, just a word to the wise wih DOHC's if you don't burn premium, you are hurting your engine. Yes., the computer will try to compensate, but why do you want to put the strain on it and your 32 valves?

Vizaracer

well, i have to run the 93 octane for sure now because i have a programmer, but when i was stock i had to run it also. that doesnt make sense to me either?

krafty02

If you add 87 to your poll I'll vote.

I still don't understand how running 93 can hurt the engine,, someone said the valves? just don't see it bro'

Run what don't make you ping, but if your tuned right, even the lower octane shouldn't make you ping.

I would never run the mid-grade either, ethanol blends are crap, just good for the environment, not good for the engine. My boat engine (Mercruiser) states no blends, either 97 or 92/93, anything in-between and they won't honor the warranty.

Remember, IMHO>

snlpa

If 87 otcane wasn't good for a stock engine the maual would say us higher octane. If it hurt the dohc 4.6's ford would be very busy with warranty work? I'll call the dealer now and ask him!! I'll brb with the answer....Ive tried 87 89 and 93 in mine and I swear on 93 I think I lost a little power.....could be in my head though...?? Now of course with a chip or timing advanced a man would need 93!!

snlpa

Here is the answer from dealers....Keep in mind we are talking stock motors no advanced timing or chip flashes! Also this is for the sohc 4.6 99-2004.

Dealer #1-use 93 (93 wont hurt it just wasting money)
Dealer #2-use 93 (always use 93 octane)
Dealer #3-use 87 (as long as your not pinging)
Dealer #4-use 87 (93 could build up carbon)
Dealer #5-use 87 (93 wont hurt it just wasting money)
Dealer #6-use 89 (87 you might ping and 93 he said can build carbon over time)
Dealer #7-use 89 (said the same thing...might ping on 87 so its better to go 89 but 93 is too high and will build carbon)

I hate to hijack the poll but.....? What dealer is correct? I think I agree with the last two. I think I'll try 89 for a while!

Jiggy_One

I always run premium 91. Im sure that if you drive your car hard here and there you will be ok with not building up carbon. I know that if I dont atleast run it up through the gears hard everytime I go out in it, than I should sell it and get a nice truck.