This 94 Mustang GT I have will only run on premium gas from Shell. Anything else and its pinging and making all kinds of racket.

Anyone have any ideas on how to get this sucker to take plain old regular gas?

I am going to try running regular and adding octane booster for my T/A.

104 octane booster!

Quoted: I am going to try running regular and adding octane booster for my T/A.

That will probably work out to be more expensive than just using the higher octane gas.

Dude, its a 302. Spend the 10 cents extra for premium. Unless you retard your timing and lower your compression, you are going to get detonation on anything less than premium. Then you will lose horsepower, which is what I assume you bought a GT for in the first place. You could always sell it and buy a Civic or be happy with one of the last remaining great factory pushrod small blocks and enjoy the horsepower. I drive a 1991 5 liter Mustang daily and it is worth it to run premium to avoid detonation and hear the sweet sound of the 302 with the windows down.

Well do you save any money having to buy bottles of octane booster though? How much does that stuff cost?

My Outback has a turbo/intercooler and requires premium. It's a real PITA.

welcome to my reality.

turbocharged cars only take premium or it'l knock and ping to holy hell, get shitty gas mileage, and dirty up my spark plugs which on a boxer motor are already a pain in the ass to change.

luckily, they are both 4 cyl and get around 30 mpg on highway.

Quoted: Dude, its a 302. Spend the 10 cents extra for premium. Unless you retard your timing and lower your compression, you are going to get detonation on anything less than premium. Then you will lose horsepower, which is what I assume you bought a GT for in the first place. You could always sell it and buy a Civic or be happy with one of the last remaining great factory pushrod small blocks and enjoy the horsepower. I drive a 1991 5 liter Mustang daily and it is worth it to run premium to avoid detonation and hear the sweet sound of the 302 with the windows down.

10 cents?  Its more like 25 cents more here.  I have purchased the premium since I got the car in 94 but with gas prices these days I would rather not now.


Which way do I twist the distibuter to retard timing on a 302?  Clockwise or counter? Its been so long I cant remember.

Combustion chamber cleaner might help.  Carbon deposits drive up the static compression and provide hot spots for preignition.

I'm a Mopar guy, so I use Mopar CCC.
neons.org/howtos/MoparCleaner.shtml

Jim

Quoted: Quoted: Dude, its a 302. Spend the 10 cents extra for premium. Unless you retard your timing and lower your compression, you are going to get detonation on anything less than premium. Then you will lose horsepower, which is what I assume you bought a GT for in the first place. You could always sell it and buy a Civic or be happy with one of the last remaining great factory pushrod small blocks and enjoy the horsepower. I drive a 1991 5 liter Mustang daily and it is worth it to run premium to avoid detonation and hear the sweet sound of the 302 with the windows down. 10 cents?  Its more like 25 cents more here.  I have purchased the premium since I got the car in 94 but with gas prices these days I would rather not now.

Sell it then to somebody who cares about performance before the motor is damaged by the low octane gas and buy a Subaru or Honda. You can probably sell it and get the same model year Civic for a couple grand less and get twice the gas mileage. Civics drive pretty good too. If you can afford it, the base model Subaru impreza of the same model year would be a little more, but worth it because it is awd.

If you really want to keep your Mustang, just retard the ignition timing a little when you run lower octane gas and you should avoid detonation. Your car will be very sluggish though. I agree that these gas prices suck, but when you mash the gas on a V8 stang, it is worth it. Are you talking about running 87 octane or midgrade? You could probably run midgrade with the retarded timing, but 87 would really be pushing it.

Good luck.

Dude, suck it up and use premium.

My '94 Dodge Intruder loves premium, now at $2.999/gal - down from $3.039 on Tuesday. I get about 3 - 4 more miles to the gallon in town and double that on the highway.

Your only hope would be octane boost. I've used the 104 Octane Boost already mentioned years ago with good luck. But haven't tried it in this car. It's not as available around here as it was where I lived 20yrs ago.

I wouldn't start dicking around with the timing on that car.

Don't feel bad, my '89 Grand Wagoneer won't run worth shit in the summer time with 87 octane either...and I only get 10mpg.

I have a '95; I usually use premium, but sometimes use regular or midgrade.   Premium does work best.  

My math skills are not the best, but lets think about this...   Lets say you get 18 MPG (I do better than that around town) and drive 1000 miles a month.   That takes 55 gallons of fuel.  If premium costs you 25¢ more per gallon than regular, it will cost you about $13.75 more a month to use premium.  

Go to Advance Auto and get a bottle of Gumout Fuel System Cleaner.  It's a clear bottle, about $6.  It cleared up the pinging and smoothed out the idle on my '87 Cavalier(4 cyl).

Quoted: Anyone have any ideas on how to get this sucker to take plain old regular gas?

Did it always knock and require premium fuel, or is this condition recent?
Any mods to the valve train?  Base timing in-spec?
Any mods to the ignition system?  (Is the computer "chipped"?)
Correct spark plug heat range?
Is the engine running hot?
Is the EGR system (if present) working properly?


That's all I can think of right now.

Empty the tank / drive it near empty.
Fill the tank with 87 octane.
Disconnect the battery overnight / clear the memory of your car's computer.
COnnect and oeprate normally, your comp will 're-learn' how to run properly on 87 octane.

And that only works if all your vehicle sensors / emissions garbage is working properly in the first place.

I think that would be on 96 or newer cars with the computer controll.  My 05 will adjust the timing automatically if I switch octane.  

That 104 octane boost stuff doesn't do what you think.  Read the fine print.  It'll take a couple of gallons of that crap to raise your octane a good amount.

BTW 99% of that can o crap is tolulene,  yep the same stuff you get at the paint store.  Octane for tolulene is 114 IIRC,  try adding a gallon every time you fill up,  depending on how much you tank holds you'll get a couple of octane points out of it.

Went and found a link for you guys about to call bullshit.

Click me

I have a 90 GT 5.0

It has the timing set back a bit - and it runs just great on the Piss they call regular here ( 85 octane with a bit of ethanol ). It has great pickup and no pinging.

Not sure of the current in town mileage, but my last Los Angeles to Vegas run got 29mpg - and continuing on to Colorado Springs yielded a over all mpg of 27.

Not much on the road is a challenge - I'm not going to try and race a Z06 or new boxer...

Best contender to date was a dual turbo WRX and we went side by side up to 85MPH on a two lane onramp where I called it quits since there was a known speed trap ahead...

If a 92 z28 can retard its own timing to allow you to run on junk gas until you find something better, then a 94 ford should be able to do the same.

There is no point in retarding the timing since you use more gas due to a less efficient engine and you may cause other problems if you go too far.

Maybe you just need a knock sensor or something simple, maybe you need to clean the carbon out of the engine, overall it sounds like the problem is more than just the high test since only one brand of high test works acceptably according to your post.

Overall I would not run low test, 86 or 87 octane, in this vehicle since its compression ratio is made for high test or whatever the factory recomended.

I am editing this because the post above me apparently got a 4 year older engine to run fine on the low test.  Use what works for you, but any high test should not ping in a stock 5.0.

My motorcylce say "91 Octane"........................... but all the gas around here is 87, 89, or 93...........

Run premium. Even of the car can retard the timing to run with regular, it won't get the mileage its would if the timing wasn't retarded.

Make sure the tires are fully inflated, and the air filter is clean.  

Just back you're timing off to 12 deg with the shunt out.  Should be able to run skunk piss with that setting. Ford didn't run Knock sensors in the mustangs with the 302 in them because they know that the FORD owners are smarter than the Mullet Men and could read the numbers on the gas pump. Not sure about the 4.6's.

That Mustang is Spec'ed for 87 octane fuel. What we used to see a lot of in the shop is carbon build up from the crap left behind from the "premium" gas. High octane = hard to ignite and less complete combustion.  On the 5.0 engines, I would set the timing to 12-14 degrees( with the "spout" plug out),  Clean the combustion chambers with a good carbon remover. Ford carb cleaner in the spray  can, put in through a vacuum line works pretty good. Does smoke like hell out the exhaust when driven after soaking.
 If you can get someone with a scan tool that can monitor pids and hopefully a Baro reading, check to be sure the mass air sensor is functioning properly. If wrong it will cause all kinds of fuel ratio problems. Check long and short term fuel trims also. neither should be more than 4% +- from zero. Also make sure there are no litle vacuum leaks from old lines that may be cracking.
If you where in NC we could get together and make that car run real good!

Another trick is to replace the processor from one out of a 93 5.0.  Seems to be a little richer and can cure some other little problems to.

If I can help explain this better IM me.  I have to work tommorow so I am going to sleep now.

Cartech, Ford Senior Master Tech.

Quoted: Another trick is to replace the processor from one out of a 93 5.0.  Seems to be a little richer and can cure some other little problems to. Cartech, Ford Senior Master Tech.

You must know a trick I dont but the only way to use a 93 and earlier EEC on a 94/95 was an adapter harness sold by pro-m which I dont think they make anymore.

I have a 95 GT and have tuned and wrenched on it since 99 trying to squeeze out more power. You should have no problem running 87 with stock timing. The 5.0 has something around 8.5-1 compression and is suited for low octane.

Some things to check are a dirty MAF(mass air sensor). A dirty MAF can affect the fuel mixture and create a lean condition. Its located in the air box and can be cleaned with brake cleaner(but carefully).

If your timing is advanced too much that will cause it. Each car is different but a stock mustang can gain alittle HP going from the stock 10 degree setting tp 14-16 degrees. Get a timing light and a manual and learn how to set your timing. Dont forget to unplug your spout connector while setting your timing. Its located by the air box.

A bad oxygen sensor(O2) could affect your tune too. Luckily there are only 2 of them on the 94/95's.

You might look into replacing the fuel pressure regulator too. Id get an adjustable one. They are easy to set and and give you a little tuneability. The stock ones probablly need replaced after so many miles anyways it could be due for a new one.

After you pick up a manual check the service milage list. Things like injectors, FP regulators, O2 sensors etc need to be replaced after awhile. Most of it isnt hard to do yourself with some research and guidence.

Just buy the premium or sell the car and get a Civic. Hell my 4 banger requires premium and I dont mind spending $3 a gallon on it to prevent detonation. I would never even consider using cheap gas in a performance car regardless of price. Hell I run premium in the lawn mower.

Quoted: Just buy the premium or sell the car and get a Civic. Hell my 4 banger requires premium and I dont mind spending $3 a gallon on it to prevent detonation. I would never even consider using cheap gas in a performance car regardless of price. Hell I run premium in the lawn mower.

You dont know what your talking about FWIW


In good running condition with factory timing setting your 5 liter WILL NOT DETONATE on 87 octane. This isnt rocket science.

Quoted: Quoted: Just buy the premium or sell the car and get a Civic. Hell my 4 banger requires premium and I dont mind spending $3 a gallon on it to prevent detonation. I would never even consider using cheap gas in a performance car regardless of price. Hell I run premium in the lawn mower. You dont know what your talking about FWIW In good running condition with factory timing setting your 5 liter WILL NOT DETONATE on 87 octane. This isnt rocket science.

I never said his 5.0 would detonate on 87 octane. I just said I wouldn't run it on 87 octane. Why run cheap gas in a performance car? Truth is a 94 GT should run just fine with no ping if properly tuned. Yet it is probably not in a perfect state of tune being 11 years old plus it is August and quite hot which will not help matters. I said "I" would gladly spend $3 a gallon to prevent detonation on "MY" car. Which will detonate on 87 octane and has no knock sensor. A little bit of ping on my 4 banger and catostrophic engine damage will occur (ie no more ring lands). His 5.0 can ping like a bitch and it wont hurt and damn thing except performance which is why I recommended selling it and buying a Civic b/c if you are going to sacrifice performance by being cheap why not get a cheap low performance car that gets 35mpg?

Why run cheap gas in a performance car?

Because its a low compression engine made to run low octane.

His 5.0 can ping like a bitch and it wont hurt and damn thing except performance

Detonation is very very bad! It WILL mess your motor up eventually especially considering his stock pistons are hypereutectic. I cracked the #4 piston on mine and had detonation problems. Of course that was running 18 pouds of boost on the stock fuel pump

Quoted: Hey guys..........news flash! Performance engines, modded engines, turbos, superchargers all that need high octane fuel. I work on ALOT of cars, ALOT of nice cars, Porsche, Audi, Ferrari, etc.........I see these owners spending huge $$$ on the car but then whining about an extra $6.00 at the gas pump, I don't understand it...............

Like I keep saying: If its mostly stock 87 octane is perfectly fine for it. Now I will agree if hes running more compression, SC, turbo or nitrous he should use 92 or higher as I do as well but this motor is low compression.

I get this octane shit all the time from some of our customers. FACT: If the engine is designed to run 87 octane then it will start easier, run smoother, make as much if not more power, and be a lot cleaner on the inside. If the engine has been modified in such a manner to require the higher octane then it should be used, otherwise it is just a waste of money.
BTW, cleaning the MAF can sometimes help a bunch. I forgot that one in my earlier post.

Oh yeah, the pcm from any of the maf equipped models up thru 95 is the same 60 pin box and should be more or less interchangable. I have a old reman PCM out of a early MAF car that I have used to verify PCM concerns on newer cars. The adapter harness from Pro-M and others (that I am aware of anyway) was to convert a none MAF car to use a MAF sensor.

It's the gas, Oxygenated as F*** for EPA crap. Figures, more expensive for worse gas. Why don't we just water it down too. My 02 Altima grocery getter pings all flippin day on 87OC (and thats what it says to use). I'm not as lucky as you, retard the timing a tad, I'll just use my 100k warranty

is it stock or rodded?

my 03 gt runs great on the cheap stuff. No problems at all

Some questions:

1.  Are you burning any oil?  Oil leaking past the valve guides due to worn valve stem seals will carbon up your engine, making it knock badly by both filling it with red-hot carbon spurs to light off the mix before TDC and by actually changing the compression ratio as the carbon really builds up.  German cars used to lose the seals at about 120k miles like clockwork, more if you used sythetic oil, but now it is closer to 200k miles.  GM is not as good, with serious wear by 100k miles, still.  Small blocks are notorious for the #7 valve stem seal going at about 80k miles and leaking a ton of oil, for instance.  I don't know Fords, so someone will need to tell me if this is relevant.  Again, I am not talking about the guide, just the seal.

2.  I would suggest GM part # 12346535 (Top Engine Cleaner).  Used as directed, it will completely de-carbon your engine.  I have used it on Porsches, MBs, BMWs (not mine, don't like them), Audis, some large GM V-8s, and a few Alfas, and it does exactly what it says that it does.  Really amazing stuff.  That and GM part # 1052627 (Heat Riser Penetrant) (like Liquid Wrench on steroids, works better than anything I have ever seen my entire life) are staples in my garage, because, you see, I am an addict.  A Mercedes Benz addict ("Hi, Op_Rod!") and it has taken control of my life.  Most recently with a second 6.9.  With the really crappy gas for the last 30 plus years, all of the engines are carboned-up when I get them, but not for long after that.  To give you an example, quite a few years ago I bought a 560SL that the friend of a friend had been given by her mother for college and she used 85 octane (Colorado, I think) to have more money for parties.  The car would now knock with octane booster and premium and she hadn't driven it much after college because of that.  I got it at a reasonable cost when she decided to buy a 300SL with a 5 speed, thinking (correctly) that it would only be sold for a year or two by MB.  One bottle of Top Engine Cleaner later, it a)stopped knocking, b)stopped burning oil, c)got much better mileage and the performance improved a lot, and d)ran so smoothly I had to check to see that it was running.  Still runs like a top, doesn't use a drop of Red Line 10W-40 and I change the oil every 10k miles.

3.  You might also try pulling the plugs the night before an oil change and using two bottles of Techron, with 1/4 poured into each cylinder and allowed to sit overnight with the old plugs regapped, brushed off, and torqued down.  The next day, run it for 45 minutes hard and change the oil and plugs right afterwards.  This is actually a Chevron-recommended technique and it will also pull a lot of crud off of the top end of the engine.  Not as much as the GM stuff above, but it will give you a good idea if that is the problem at a lower cost.

4.  Use a product made by Power Research (www.priproducts.com) called PRI-G to gradually clean out your engine.  Works nicely to clean up the crud in your fuel system, on the valves, and a lot of the engine carbon, seems to increase octane but actually is just making the gas burn more evenly. I have used it for years on very expensive cars and it works great.  Also keeps the gasoline from aging which is important if you have a bunch of cars that aren't driven every day (which I do) and you live in an environment that ages gasoline fast (Houston) and you are forced by the EPA to use reformulated gas with MBTE (yup, Houston is a "non-attainment area" and  thanks to former Mayor Lee Brown, the Lee Brown of the Lee Brown Crime Lab Scandal, who refused to fight the EPA at the time so that we now have to work within the EPA ruling).  Highly recommended.

5.  Do you index your plugs so that the gap faces the inside of the cylinder?  It makes a difference, sometimes a large one, in how evenly and smoothly the engine runs and whether or not it knocks.

6.  Are you using good plug wires?  Are you using an aftermarket ignition designed for "racing" (they usually aren't, but they will say that they are)?


When I lose all self control and shame and buy yet another classic Benz, I am always told that I have to use premium because it knocks less on premium (but it will knock a little even with premium) (93 in Texas).  After indexing and gapping the plugs (and usually Jacobs wires), it knocks a lot less.  After a few tanks of PRI-G and a change of fuel filters, even less so.  After making sure that the timing is correct (and usually using a Jacobs ignition system), the knocking is only on hard throttle.  Then I run the GM Top Engine Cleaner through and change the oil and presto, no more knocking.  With regular use of PRI-G, no more knocking, ever again because I don't have any deposits.  I think that this adds $.04 per gallon to the cost of my fuel.  And, in a pinch, I can use regular and it will only knock a little in any car I have de-carboned.

The folks that know have told you it should run correctly on 87.  Do you think anybody ever replaced the innards with some high compression parts?  Or is it still stock?  Anyway, maybe you could achieve a balance trying an old trick my chemistry teacher hipped me to.  Half a tank of 87 and half a tank of 93 ='s 90 octane.  I used to do this. You get a point higher than mid-grade 89 and worked out to a penny a gallon cheaper than 89.  Don't know about this with today's prices!