Quick quesion about fuel

sorry about the subject typo, or any others.. I was tired.. anyway..

also, and benifit of using the 90 octane.. Paying more for gas even if it does get you more mpg is pointless.. but if it's better for the motor...

when I looked over and noticed the octane rating, 86.

The octane rating is just an indicator of the gasoine's ant-knock properties, not its power (a higher octne rating does not give a vehicle more ooompf). If you experience knocking or pinging on the 86 octane fuel, then move up to a higher grade. Otherwise, you're just wasting your money. I've only had one vehicle that required higher octane fuel than the manufacturer recommended so while it can happen, it's rare.

well thats just it I think my truck might be pinging, seems like I heard it doing it the other day under load.. (tho i'm not sure exactly what it sounds like)

Adair

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Quick quesion about fuel Group: alt.autos.4x4.chevy-trucks Date: Tue, Oct 7, 2003, 4:50am (CDT+5) From: snipped-for-privacy@hotpop.com (Adair=A0Winter)

I was filling up with gas tonight and I was pumping Reg. unleaded as always, when I looked over and noticed the octane rating, 86.

Last week I was fipping through the owners manual that came with my '99 K

So this might be a dumb question, I can't imagine 1 point less would hurt anything, but would I gain anything buy using the 88 octane? (at 10 cents more per gallen)

I don't know if it would help anything, but if it would help my milage or just be easier on the engine thats all good for me.. I am about to change the oil in her for the first time (since I've owned it) and I'm going to go with mobil 1 5w30. as well as using a can of restore after I break in the mobil 1. I will also slowly change all the fluids over to synthetic as they come due.

I will also be adding a cat-back system sometime soon.. looking for all the MPG I can get outta her. :) plus longer life..

Adair ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

(in a follow up post) Group: alt.autos.4x4.chevy-trucks Date: Tue, Oct 7, 2003, 5:03am (CDT+5) From: snipped-for-privacy@hotpop.com (Adair=A0Winter)

sorry about the subject typo, or any others.. I was tired.. anyway.. also, and benifit of using the 90 octane.. Paying more for gas even if it does get you more mpg is pointless.. but if it's better for the motor...

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

( rich replied with this info)

snipped-for-privacy@webtv.net (Rich=A0B)

The octane rating is just an indicator of the gasoine's ant-knock properties, not its power (a higher octne rating does not give a vehicle more ooompf). If you experience knocking or pinging on the 86 octane fuel, then move up to a higher grade. Otherwise, you're just wasting your money. I've only had one vehicle that required higher octane fuel than the manufacturer recommended so while it can happen, it's rare.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ (which pulled a tooth from Adair...revealing this diagnostic note....) snipped-for-privacy@hotpop.com (Adair=A0Winter)

well thats just it I think my truck might be pinging, seems like I heard it doing it the other day under load.. (tho i'm not sure exactly what it sounds like)

Adair ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Adair, first things first.......

The octane rating is a MINIMAL rating for the fuel coming out the pump. In most cases the actual rating WILL be higher than what is posted on the pumps. You won't see a 3-4 octane deviance in what is posted, but it's very likely it will be 1 higher than whats posted. If the fuel wasn't mixed in this manner, there would be an arse of stations out there getting fined when "The Man" checked their pumps. Something which is done on a regular basis by inspectors. So rest assured that the fuel you were pumping, was most likely meeting what was in your book.

Now..........on to the ping..............

Before you go forking over 10 pennies of your hard earned money, on a gallon of gas, be sure to do your maintenance first. A neglected oil change CAN affect the combustion process, especially on a higher mileage vehical. So go ahead and get the old oil out, do a good tuneup with ALL your filters, change your worn primary and secondary ignition components if you've neglected it in the last 3-4 years, clean your fuel system, and get the air-fuel-fire system in good order. Do all your prevenatives first, insureing that the ping isn't still going to be driving you crazy "thinking" it could be in the basics. Then..........do your exhaust system....... insuring the breath the vehical takes isn't going to be restrained on the exhale.

Then......."IF"....the ping is still there, go to a higher octane rating. I think you're going to find that it isn't going to be neccessary with the fine tuned vehical, as long as your not burning oil, and the engine is'nt on its way out as far as ring clearances and valves go.

A SUGGESTION..........4-U......

I would highly recomend that you consider installing a new catalytic convertor during the exhaust replacement. If you are going to the expense of a Cat Back system, dualing it out all the way back, you would be well advised to consider biting the bullet and spending the extra money on installing a "high flow" convertor to let the engine breathe to full potential. Just a thought.

hopefully informative

Scrib Abell ~~a dare........has been confronted~~

Yes but todays computer comtrolled motors take feedback from the ping sensor to trottle spark advance if necessary. In my corvette I can feel the difference with I sink my foot into it with high octane gas. You can smash the pedal without having to worry about preignition spoiling the fun. It could have fuel milage benifits if it allows the motor to run with more spark advance during part trottle cruise. But usually not enough to offset the premium in price you pay over the lower octane gas.

Adair,

My experiences with multiple vehicles on low, mid and high octane fuels. With EFI vehicles, higher octane = more spark advance = more power with less throttle. Nine times out of ten this difference is imperceivable, but if you're running a built motor w/higher compression you can certainly feel the diference. The below is for bone-stock vehicles.

I've tested all of my vehicles and this has held true thus far: you'll get more MPG with higher octane fuels, but this miniscule gain in economy is less than the difference in price. So in short, it's not really worth it. My truck runs like ass on 87, runs perfect on 89, and runs the same as 89 on

Refresh me on your YMM? If it's an older style TBI system (87'-95'), I've found that running 89 octane with the timing bumped 4* (spec is TDC, I have mine running at 4*BTDC) gave me more oomph and a few MPG more. If you have a newer truck with a camshaft position sensor don't try this! The only way to advance the curve on the newer motors is flashing the PROM.

Doc

I am curious as to where the 86 octane fuel was being sold, its brand, and the elevation above sea level at that location.

Higher elevation means thinner air. Except for turbos that pressurize the intake manifold to correct for thinner air, thinner air means that the whole engine works less hard and the octane requirement of the engine is therefore reduced (along with its power).

Oil companies know this and, to save money, blend gasolines with less octane for sale in high elevation areas. For example, premium at east coast sea level is usually 93 octane, but in a place like Santa Fe New Mexico may be more like 90 or 91 octane (I don't know for sure. Its been a long time since I have been there).

To my knowledge, the only gasoline under 87 octane that is sold at low elevation east coast stations is the economy sub-regular Sunoco.

I live in the panhandle of texas, aprox. height above sea level is 2800 to

Adair KD5DYP

grr, I forgot, it's also a texaco station, i think....

Adair

Good answer, what was the "one" vehicle if you dont mind?

Hatt

It was a 1985 Celebrit with the 2.5 liter cylinder. I just could not get it to use regular gas without pinging. I tried different things and even took it to the dealer several times and neither of us could find a reason for it to be pinging. Then I found out that a co-worker had the same problem with his 1985 Celebrity 2.5L and I just lived with it (for 155,000 miles).