OK to use 87 octane if there is no ping?

Young1 · #1 (**permalink**) 06-29-2013, 11:54 AM

I am weaning my iron head 9.8 compression FE off 91 octane. Ran over a thousand miles with 89 and no ping. 38 degrees advance all in at 2800 rpm. Right now I am using a mix of 87 and 89 for 88. As long as it does not ping am I ok to burn 87? Any other side effects to watch for?

MJJ · #2 (**permalink**) 06-29-2013, 01:21 PM

Why? To save .30 a gallon?

redmt · #3 (**permalink**) 06-29-2013, 01:31 PM

I ran whatever gasoline in a stock 428 in a 1 ton 4x4 work truck for well over 30 years and never lifted a valve cover. The bores had .007 taper and a couple of the exhaust valves didn't look so great when I tore it down last year but it was probably well over 100k miles.

WardL · #4 (**permalink**) 06-29-2013, 02:18 PM

If it is not knocking/pinging the gasoline is suitable for your engine. Just make sure you can hear the knock if it does knock. Between my poor hearing and a loud engine there is no way I can hear knock/ping in my engine. The engine knock will occur under load, so at idle you may be fine but going up a hill at freeway speeds the engine knocks and you can't hear it. The other thing to remember there are other factors that contribute to minimum octane requirements: Increases with age of engine, timing (you could retard your timing a little to reduce your octane requirement), cam, elevation, etc.

RET_COP · #5 (**permalink**) 06-29-2013, 06:40 PM

It's very hard to know over noise how close the engine is to ping/detonation. With the inconsistencies in the quality of gasoline, it's not worth the few bucks in savings when the higher octane is just another button to push at the same pump. The inconstancy was told to me by a former VP fuel distributor about pump gas- he had no faith in it.

Remember just because an engine has a low compression ratio does not always mean that it is NOT prone to detonation, it could be the opposite.

mdross1 · #6 (**permalink**) 06-30-2013, 07:19 AM

Quote:

Originally Posted by RET_COP

It's very hard to know over noise how close the engine is to ping/detonation. With the inconsistencies in the quality of gasoline, it's not worth the few bucks in savings when the higher octane is just another button to push at the same pump. The inconstancy was told to me by a former VP fuel distributor about pump gas- he had no faith in it.

Remember just because an engine has a low compression ratio does not always mean that it is NOT prone to detonation, it could be the opposite.

My feelings also with so much noise in these open cockpit cars it would be hard to hear light pinging.Aluminum heads help with upping the threshold of pinging.I always wonder what comes from the gas pumps especially as greedy as big oil is.

Young1 · #7 (**permalink**) 06-30-2013, 03:48 PM

I will stay with 89. More prone to light ping with 87 when hot in summer too.

cdog · #8 (**permalink**) 06-30-2013, 11:00 PM

I'd use the highest octane you can get... 93 if available.

Ron61 · #9 (**permalink**) 07-01-2013, 03:50 AM

If you have had your valve seats hardened for the junk they call gas now you might be ok with the lower octane but I would stay with the highest I could get at the pump. The highest we can get up here is 91 and if you test that, most of the time it is closer to 88. You can buy a tester to tell you how much of the so called Ethanol and other junk they use for filler pretty cheap and it is amazing at how it varies from one station to another, even the same brands. I go to the outlet and buy 94 unleaded octane for my lawn and garden equipment as it has no Ethanol in it. Works great in the car when mixed with the pump stuff too.

Ron

Bartruff1 · #10 (**permalink**) 07-01-2013, 06:43 AM

Quote:

Originally Posted by MJJ

Why? To save .30 a gallon?

I only burn about 100 gallons a year, so for me, $30 is not worth the trouble of even careful listening. I haven't done the math, but I suspect that is less than 0.1% of my annual cost.

I do go through the trouble of burning only non ethanol, that is no problem at home and most of the time with a internet search I can find it on the road.

jhv48 · #11 (**permalink**) 07-01-2013, 08:27 AM

With the massive amounts of time and money we throw at these cars and engines, I'm having trouble understanding why in the world anyone would want to save a few pennies on fuel octane with the potential cost of engine destruction. Where I live, a twenty gallon fill up with regular gas would save you $4.00 over premium. Not even enough for a cup of Starbucks coffee.

In my opinion, and that's all it is, if you can't afford to put premium gas in your baby, you probably shouldn't own one.

Roush #1 · #12 (**permalink**) 07-01-2013, 10:01 AM

If you are judging your engine octane requirements by "pinging" and are lowering the octane until you hear a ping, I would suggest you start researching engine builders as you are going to need one soon.
You can damage your engine extensively by saving a few octane bucks which is what it sounds like you are trying to do.
I would also suggest you start a new topic explaining what you have done to lower the exhaust sound enough to hear a ping. ;-)