I have never ran anything put 91. I would be really careful with running 89. It could be pinging and you may not be able to hear it. There for it will hurt your motor in the long run. However I could be wrong hopefully people that have done this will chime in!

 

Don't run 89. If you can't afford premium fuel, don't drive the car.

 

I've been filling up with 89 Octane lately with super prices being out of this world. I haven't noticed any dentonation or anything...but has anyone experanced any problems running a lower octane?

Me too with no noticable problems.
Scott did you ever get the tech manual in CD?
You need to stop by and check out my 03 FSVT, and the HID's on the 02.

 

You're saving about $1.00 per fillup and creating a good chance to screw up your car. Is that smart?

Lee

 

You're saving about $1.00 per fillup and creating a good chance to screw up your car. Is that smart?

Lee

I don't think so, and wouldn't advocate it. I wouldn't think there is a good chance but why take any chance. Actually it was filled up with 87? I think by error a couple times by my daughter this past week. Reacted fine and I've since topped off with 93.

 

I've been running 89 since the Ford Tech told me I was pissing away $ for a couple of HP. The car runs fine. It has 12K on the clock since I switched and no issues related to fuel. In some states 89 is the same as 91. Like I said 12K on the clock with no issues. I have no idea if being at sea level means anything though?

 

Don't run 89. If you can't afford premium fuel, don't drive the car.

Well how the hell am I supposed to get to work?

I'm just being cheap and 89 is just mix of left over 87 and 91 fuel anyway from the truck.

Anyway does anyone know if the car has a knock sensor on it? I dont think it does.

 

I'm just being cheap and 89 is just mix of left over 87 and 91 fuel anyway from the truck.

Anyway does anyone know if the car has a knock sensor on it? I dont think it does.

The latest Focus Fanatic magazine ran an article on an SCT tune for the SVTF. SCT was able to get some decent gains by tweaking the sensitivity of the ECU's knock retard feature, so I gather that the engine definitely has one.

The difference between 89 and 91 at most gas stations is about $0.10. For your average fill-up, you're talking about a bit more than $1.00 each time. If you go to the gas station once a week, you're saving $52.00 a year.

The downside, at best, will be reduced power due to increased knock retard. Increased KR can also lead to lower fuel efficiency, which might easily offset the $1.00 you saved at the pump. At worst, if you're running WOT and the knock sensor hiccups (not likely), you could run into some detonation issues that will destroy your engine.

89 octane is usually a mix between the 87 and premium grade fuels at the gas station. That doesn't make it good; 89 octane is certainly less resistant to knock than 91, and like I said, you may actually suffer in the mpg department. IMO, it's not worth what little savings you might see in your wallet. You'll pay for it in other ways.

 

Earlier this year, USA Today ran a front page story in the money section about this issue. A number of techs commented that car companies indicate premium is required, as this is the only way to get the advertised horsepower out of any given car. They also mentioned that you would have to be a NASCAR, or NHRA driver to notice any real HP decline, and that they average driver wouldnt notice the difference with lower octane. I believe they had a Nissan tech that said that no harm would be caused to any engine by running 89 octane. I still use premium, even at 2.45 a gallon, but will mix a few tanks with less octane once in a while. Never noticed any difference at all.

 

The difference between 89 and 91 at most gas stations is about $0.10. For your average fill-up, you're talking about a bit more than $1.00 each time. If you go to the gas station once a week, you're saving $52.00 a year.

I fill up about 3-4 times every two weeks. MPG has been about the same if not better then what i've been getting.

 

The difference between 89 and 91 at most gas stations is about $0.10. For your average fill-up, you're talking about a bit more than $1.00 each time. If you go to the gas station once a week, you're saving $52.00 a year.

I fill up about 3-4 times every two weeks. MPG has been about the same if not better then what i've been getting.

better mpg???

well that just doesn't make any sense

 

look, if you know your physical chemistry it is quite simple why you need the better gas. But, theoretically the knock sensor should retard timing, lost HP, and still drive okay. But you never know. I wouldn't run anything else but 91+; I did once, and was nervous for a week.

 

now i'm sitting here after reading this going wtf? someone should call svt and see what they might say? I would be a nervous wreck too if i put 89 in mine worrying the whole time if it was knocking and i can't hear it...

this gas price thing, does suck the big one, i was liking filling up for under $20 bill.....not anymore....son of a...

joe

 

I fill up about 3-4 times every two weeks. MPG has been about the same if not better then what i've been getting.

That amounts to about eight times per month, or $96.00 a year. Suppose you filled up twice as often -- you're still saving less than $200.00 a year. To most SVTF owners, who willingly paid a couple thousand over the price of a ZX3 or ZX5 for performance, that shouldn't be a very big deal. Gas prices keep rising, but the difference between fuel grades seems to stay about the same.

How hard do you drive your car on a daily basis? At lower RPM, and with more sedate driving, I would think that lower octane fuel is sufficient to prevent knock from causing any serious timing retardation. That may be why you're not noticing much of a difference and why you haven't seen a change in MPG.

I have less than 1000 miles on my SVTF so I haven't had much chance to play with octane, but I did experiment with it on a 2000 Pontiac Grand Prix GTP that I owned a few years ago. Running anything less than premium gas caused a very noticeable dip in power and mileage, to the tune of almost 3-4 mpg! Granted, the engine in that car is supercharged from the factory, but the principles at work are all the same. Less knock resistance -> increased knock -> more knock retard -> less performance -> worse MPG, unless you're not pushing the engine hard enough to cause much knock in the first place. From what I've read, the stock knock sensor provides a ton of feedback to the ECU even on premium fuel, so it isn't unreasonable to guess that running lower octane would cause even more KR.

 

now i'm sitting here after reading this going wtf? someone should call svt and see what they might say? I would be a nervous wreck too if i put 89 in mine worrying the whole time if it was knocking and i can't hear it...

this gas price thing, does suck the big one, i was liking filling up for under $20 bill.....not anymore....son of a...

joe

Here's how I see it. It's in the manual use 91+, it's on the gas door 91+, it's on the gas guage "Premium Fuel ONLY", it's was told to me by seven different people at the dealership when I bought it including the owner of the dealership, the head service tech, and my sales guy, and SVT say's it is a must to use 91+, now if you're that cheap to save a buck a tank

go return the car buy a regular ZX3 and give the SVT to somebody worthy of having it and taking care of it how it should be.

 

If it pulls timing, beware of carbon buildup. That 50 bucks you save this year could cost you much more down the road. Use 91. If you can't afford it, sell it and buy a ZX3.

 

If it pulls timing, beware of carbon buildup. That 50 bucks you save this year could cost you much more down the road. Use 91. If you can't afford it, sell it and buy a ZX3.

IIRC, The cost of new plugs outweighs the $50 you save a year.

-Mark

 

The latest Focus Fanatic magazine ran an article on an SCT tune for the SVTF. SCT was able to get some decent gains by tweaking the sensitivity of the ECU's knock retard feature, so I gather that the engine definitely has one.

The difference between 89 and 91 at most gas stations is about $0.10. For your average fill-up, you're talking about a bit more than $1.00 each time. If you go to the gas station once a week, you're saving $52.00 a year.

The downside, at best, will be reduced power due to increased knock retard. Increased KR can also lead to lower fuel efficiency, which might easily offset the $1.00 you saved at the pump. At worst, if you're running WOT and the knock sensor hiccups (not likely), you could run into some detonation issues that will destroy your engine.

89 octane is usually a mix between the 87 and premium grade fuels at the gas station. That doesn't make it good; 89 octane is certainly less resistant to knock than 91, and like I said, you may actually suffer in the mpg department. IMO, it's not worth what little savings you might see in your wallet. You'll pay for it in other ways.

This is spot on!

Yes we do have a knock sensor, and it pulls timing GLOBALLY. So if one cylinder pings, it pulls timing to All cylinders decreasing power.

I have nothing else to add that Blee didn't cover perfectly.

 

If you can't afford it, sell it and buy a ZX3.

and how does that solve my problem by getting a new car? By spending even more money?

Well after what I've been through with the car and how much of mechanical headache its been for me, I'm planning on dumping it ASAP for a new Mustang...and yes the 98 GT I had was cheaper to operate since they roughly got the same MPG during my commute to work and the difference between regular and super added to the equation

 

If you are unhappy with the car and there has been a lot of problems with it then I would get rid of it. However I would try to claim it under the Lemon Law so that you don't take a hugh loss on it.

However on the other hand I would not let gas mileage hold you back from having fun and enjoying your car. After all no matter what you do you are going to need gas in the car to get around. So just get in the car turn the key and hit the gas and enjoy it!

 

I've been filling up with 89 Octane lately with super prices being out of this world. I haven't noticed any dentonation or anything...but has anyone experanced any problems running a lower octane?

Not a problem.

http://www.myfordfocus.com/forum/showthread.php3?threadid=15524&pagenumber=1

 

Don't run 89. If you can't afford premium fuel, don't drive the car.

I am guessing you still live with your parents.

 

You'd be wrong, fog.

If his car pulls timing he could definitely get some carbon buildup - the least expensive repair would be to replace the plugs if they foul (and they run about $15 each).

 

I highly recommend using 87 or below. Leaves more parts for the rest of us. BTW there has to be knock for the knock detector to work. By the time it activates it's already to late. That, and you might not notice the knock. With that said, I'm sure there won't be any knock. Go for it

 

now i'm sitting here after reading this going wtf? someone should call svt and see what they might say? I would be a nervous wreck too if i put 89 in mine worrying the whole time if it was knocking and i can't hear it...

this gas price thing, does suck the big one, i was liking filling up for under $20 bill.....not anymore....son of a...

joe

Here's how I see it. It's in the manual use 91+, it's on the gas door 91+, it's on the gas guage "Premium Fuel ONLY", it's was told to me by seven different people at the dealership when I bought it including the owner of the dealership, the head service tech, and my sales guy, and SVT say's it is a must to use 91+, now if you're that cheap to save a buck a tank

go return the car buy a regular ZX3 and give the SVT to somebody worthy of having it and taking care of it how it should be.

The service advisor at the dealer I went to didn't even know SVT requires the SVTF to run on 91 octane

.