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  Gurgling/Rattling sound...'knocking'?

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Author Topic:   Gurgling/Rattling sound...'knocking'?
71ragtop
Forum Kahuna

Posts: 1102
From:Atlanta, GA
Registered: May 99

posted 09-29-2000 10:22 AM     Click Here to See the Profile for 71ragtop   Click Here to Email 71ragtop     Edit/Delete Message   Reply w/Quote
So, I listened to some of the folks that said I should be able to run my GT on the mid-grade gasoline. 87 octane, instead of the 92 or 93 that I normally run. While driving around this week on the 87, I noticed that if I have to go above 3500 rpm for any reason...I hear this gurgling/rattling sound...is that what knock sounds like? My timing is not advanced, its at the stock position, as far as I know that is. I haven't put a timing light on it. Anyhow, it doesn't do it when I run hi-octane fuel.

So I will be going back to premium today when I fill up.

Just thought you all might like to know in case you wanted to try to save some money at the gas pump.

Mike

IP: 38.30.8.1

Stewart
Esteemed Member

Posts: 1826
From:Monterey, CA
Registered: Apr 2000

posted 09-29-2000 11:43 AM     Click Here to See the Profile for Stewart   Click Here to Email Stewart     Edit/Delete Message   Reply w/Quote
Mike, that sounds like pinging. It happens to different cars with different gasolines, but the major reason can be blamed on the grade of gasoline.

For example, if I put gasoline from a "cheapy mart" type operation (7-11, Beacon, Ultra Mar) in my Crown Vic's engine, then my engine will ping. It doesn't happen if the same gas is put in my 5.0, or my fathers Toyota Avalon. I don't know why it affects my Vic and not my 5.0. But sometimes it even happens to my Vic when I buy gas at a "major mart" like Chevron. But that's very rare.

Whats the main cause? It's the grade of the gasoline being purchased. A chemical engineer type dude who worked for Mobile Oil told me (when I was a teenage "pump jocky" working at a gas station) that during the process of turning crude oil into usable petroleum products, different grades of the product are produced.

For illustration purposes, I'll use the designators A Grade, B Grade, and C Grade.

The A and B Grades, when processed into gas, are of a much higher quality than C Grade. The C grade is normally purchased by the "Mom & Pop" operations, the "cheapy marts" etc. The A and B Grades are usually used almost exclusively by Shell, Chevron, Union 76, etc. If I remember correctly, the "majors" aren't even allowed to buy the C Grade for their stations.

Naturally, because the C Grade is purchased at a cheaper rate than the A & B grades, the price of the gasoline at those places is usually a little lower.

Anyway, it's this different quality (grade) of gas that can effect the performance of a car too.

Not saying you didn't buy the gas at a "major" station...just trying to share stuff with y'all!

Stewart

[This message has been edited by Stewart (edited 09-29-2000).]

IP: 64.12.104.162

mustangs68
Forum Kahuna

Posts: 8144
From:Phoebus Virginia,USA 1968 Fastback & 1995 Vert MCA#39406 M&M #12
Registered: May 99

posted 09-30-2000 10:57 AM     Click Here to See the Profile for mustangs68   Click Here to Email mustangs68     Edit/Delete Message   Reply w/Quote
If it ain't Texaco..it do't go in my cars

geee loyalty or what!!
sam

IP: 209.240.221.55

71ragtop
Forum Kahuna

Posts: 1102
From:Atlanta, GA
Registered: May 99

posted 10-01-2000 12:39 AM     Click Here to See the Profile for 71ragtop   Click Here to Email 71ragtop     Edit/Delete Message   Reply w/Quote
Thanks for the details Stewart.

I filled up with 93 octane and the pinging went away as I thought it would.

Mike

IP: 38.30.8.191

GTRocks
Esteemed Member

Posts: 177
From:Lusby, MD, USA
Registered: Jun 99

posted 10-02-2000 11:09 AM     Click Here to See the Profile for GTRocks   Click Here to Email GTRocks     Edit/Delete Message   Reply w/Quote
You can't give a man tenderloin for 5 years, and then suddenly switch to sirloin steak and think he ain't gonna complain!!!!

IP: 207.159.104.52

71ragtop
Forum Kahuna

Posts: 1102
From:Atlanta, GA
Registered: May 99

posted 10-02-2000 01:43 PM     Click Here to See the Profile for 71ragtop   Click Here to Email 71ragtop     Edit/Delete Message   Reply w/Quote
Never thought about in terms of a steak...but that definitely hits close to home. Thanks for the new perspective.

mmmmmmm....Beef.....It's whats for dinner...

Mike

IP: 38.37.15.188

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