Astounding mileage, Pt. 2

If it doesn't ping on regular or mid grade, then using premium is a waste of money. A car should run on whatever grade is specified in the owner's manual. If it doesn't run right on that grade, it needs a tune-up. Using a higher octane then specified does nothing.

Joe Calypso Green '93 5.0 LX AOD hatch with a few goodies Black '03 Dakota 5.9 R/T CC

if it pings on 89, it will get better mileage with 91. Or you could adjust the timing.

My son had the same car, and he had EGR problems but while he had the check engine lite, he swears he got close to 35 on a 30 mile round trip commute.

That engine was designed for the corp CAFE standards.. that's why it's called the HSC.. high-swirl-chamber

Ah, wondered about that HSC thing. I'll check the timing.

Sounds like octane, from what everyone has told me, is indeed just as much as you need, otherwise it's a waste of $.

That's why I am the world's foremost authority... I know just enough to know "too much" about everything... TOO much trivia retention!

...also why I know those CBS docs are fake and also why Dubya didnt cost the taxpayer a dime, or "desert", when he dropped out of the flying reserves.. but that's another story. :)

If the engine likes more timing you can advance your timing curve to get more performance and mileage out of it. Take note that I mean as much timing as the _engine_ likes, not how much timnig ti will take before pinging. I used to run 94 octane in my '68 302 with closed chamber 289 heads (high compression). I went through the distributor, put in a Pertronix unit, changed to colder plugs, and some other misc stuff. The goal was to get the most power out of it as I could but run on 93 octane, preferably 89 if I could do it.

I tuned my advance curve a bit and I get more power now. Though with 94 octane I can advance the timing more and still not ping, but I don't get any more power, in fact it actually drops off in power. The reason being that the timing is advanced beyond where my particular combination of parts will make the most power. So I retarded the timing until the power came back up and I got the best performance. Then I tried running 93 octane, and it doesn't ping on 93. So I tried 89. It will ping a bit under high load, part throttle, low RPM conditions.

I can put a slightly heavier spring in the distributor and make it run on 89 with no pinging, but it's worth the extra $2 or so per tank of gas to get that last bit of performance. I need it when that tiny little engine is pulling my two-ton Galaxie with no help from the 2.80:1 gears.

As far as your timing curve, when an engine makes the most power it will get the best fuel economy. I've seen as high as 16.4 MPG from my Galaxie. That's with a 600 CFM Holley vacuum secondary carb. With the original engine running on 7 cylinders with an Autolite 2100 1.23 venturi carb (stock was

To give you an idea of what a properly tuned advance curve can do for your mileage... When I first got my '68 the vacuum advance can was a stock advance/retard unit, the retard side didn't work (a good thing, it was for emissions and hurt performance and economy). I got about 7-8 MPG from the original 302. At that time it was running on 8 cylinders, though #5 was a bit weak. It used 89 octane, as it would diesel on 87 (I could get it to not ping on 87, but it would still diesel). Anyhow, after getting a new adjustable vacuum advance can and tuning the vacuum advance to get the most power out of the engine I got 12-13 MPG. After doing a full tune-up and putting on a rebuilt Autolite 2100 1.23 venturi carb I was getting 14-15 MPG with my typical driving. Having an optimal timing curve can work wonders for performance and economy. Often times the timing curve cars come with from the factory are not optimal for performance and fuel economy for emissions reasons (to meet emissions standards they have to sacrifice some mileage).

Cory

This is what I did with my '67; with recommendations from my father, who owned two 6-cyl '66s, and a bunch of other old stuff he liked to fiddle with, I changed advance springs and initial timing. It runs fine on 89 and I do get more power out of it.

Though with 94

Interesting... makes sense. My combo was 12* BTDC and full advance at

No kidding... : )

I've found that I get, with a 600 Edelbrock, vac. secondaries, 5-speed and 3.80 gears, around 13 in town (revs are higher on avg.) and 17 on the highway. I imagine at 55 - 60 in 5th I could get 20, but I don't want to bog the motor, so I don't use 5th until I'm around 3000 in 4th (60). I have a mild cam in the motor and other improvements... windage tray, roller chain, K&N. I think K&Ns give you probably 1 mpg, maybe 2.

Yikes

Anyhow, after getting a new

Thanks for your recommendations. I have noticed an increase in economy since I last changed the initial timing and put in the "looser" springs, with no ping on 89... I don't know if I can really expect much better mileage out of it, because of how it's geared, but then again, mileage was a secondary concern. Efficiency in the true sense of the word is definitely not a secondary concern, and I wonder how close I am to optimizing that... I am continuing to learn. When I had the Autolite rebuilt in my first 67, and addressed other problems, I did get 2-3 more mpg with C4 and 3.00 gears than I do now, in good tune... and not getting on it... not too shabby. Of course, the 302 is lugging around at least 1000 fewer pounds in the Mustang, maybe more like 1200