Timing for lower octane?
 

Given rising gas prices, can a stock 91 5.0 be timed to run on 87 ocatne gas? I'm currently set to 14 for 93 octane. I know 10 degrees is stock. What should it be set to for 87 octane or mid-grade? Can it be done? I hate spending the cash on high test since I'm mostly highway driving now.

Re: Timing for lower octane?
 

12 degrees for the middle gas
10 degrees for the cheap one

Re: Timing for lower octane?
 

If your going to use mid grade, why not just go ahead and get premium? think about how much more money it is? it's a dollar and some change per fillup?
Now In a daily commuter, I would use 87 octane, because I could bet the (monthly) savings would be noticeable, other than that, Id stay with midgrade on 14 degrees, as long as you drive easy, I dont think you would detinate.

I have probaly 16 deegrees of timing, and usually run mid grade for short easy trips, when it's 100+ degrees hot out, i try and stay with the 93 octane, at the track I try and buy me a 7$ a gallon 103 vp for peace of mind.:)

Re: Timing for lower octane?
 

I don't drive mine that often and when I do it's mostly to work ( about 20 min drive) anyway my timing is at 20 degrees and I always use 93. Short or long distance drives.

Re: Timing for lower octane?
 

well, It really isnt safe what i do, i could be detonating more than i notice using mid grade and 16 degrees, but it's something i been doing for years now, Everybody's car is different. Also I have low compression, and im sure that helps.

Re: Timing for lower octane?
 

The cost difference betwen 87 and 92 ranges from 14 to 22 cents here in Minnesota. The interesting thing is that that spread always seems to be there. Even when gas was 1.20 a gallon for 87, premium was 1.34 to 1.42. Taking the worse case, you would be spending 18% more to get premium. Gas just hit 3.20 a gallon for 87 yesterday. Premium is now 3.42. Now it's only 7% more to get premium. It's a better deal. If you emptied your tank once a week for an entire year, that's only an extra $176 for the year or about $15 a month. Do you really want to de-tune your fun for $15 extra a month?

We can also purchase non-oxygenated premium here in Minnesota. That means it's pure gasoline. I get at least 10% better gas mileage when I use it than when I use the oxygenated crap. It's actually cheaper for me to use than if I detuned my car to use 87.

Vamp89, Why is your timing set so high? Have you put your car on a dyno to confirm that you get the most average HP at that much advance?

Re: Timing for lower octane?
 

I made 301 RWHP and 330 RWTQ on 87 octane with no detonation at 14 degrees of initial timing.

Re: Timing for lower octane?
 

No detonation on a DynoJet? If that's what you mean, don't forget that a DynoJet doesn't properly load the engine to test for detonation. That's what Mustang Dynos are good for, however.

Re: Timing for lower octane?
 

Well considering I raced the hell out of that engine on 87 octane and never had an issue one in 3 years I would say it was running fine. Mid 12's @108 mph. It would start to detonate at 16 degrees of initial timing with 87 octane.

I ran 93 octane and bumped the timing as high as 18 degrees initial but it ran the fastest at 14 degrees and 87 octane.

I tweeked it out over the course of a couple hundred 1/4 mile runs.

It could have something to do with the crappy air where I am at.

3000-5700 ft density altitude.

Re: Timing for lower octane?
 

She run better set that high.

Re: Timing for lower octane?
 

That makes sense.