Switched gas and now she backfires

Zendalar · 06-25-2002, 10:39 AM

Tell me what on earth is going on.

This morning I was still driving with 99 octane fuel, or so I thought. Car worked like a charm.

This afternoon I had to switch to 98 octane with "lead additive" because the gas station had dis-assembled the 99 octane pump because there was no profit in keeping it.

I put about 30 litres (with additive) in car and now the car is backfiring, when rolling without load.

I called the place where I bought the gasoline and they said that they have no clue, because the "99 octane" they used to sell was infact same leadless 98 octane only with the additive already added.

So basically it was the same gas that I had put in my car today, and now it pops.

Only thing that I can think of is that the gasoline brand was earlier Shell, and now ESSO.

Any other ideas? Can there be so huge difference? (My other car does not mind what gas I put in)

addictionMS · addictionMS's Garage

98 and 99 octane, try living in California wehre we just lost 92 octane and got 91 octane. None of my cars are rated for octane that low.

Boy, I sure wish we coudl buy gas over the internet

Jim

paulhagedorn · 06-25-2002, 02:22 PM

I am going to guess that it isn't 99 octane??? Rather whatever the one is MON or RON. Not sure though.

I know Cali is screwed up and such, but what is the point in not having gas that is 92 or 93 octane. Is it that they dilute real gas with so much crap that it goes below 93 octane? Doesn't all gas start off at the same octane and is diluted to what the companies want along with the respective additives?

My father had an experience with shell when he was in the army that was a very bad one. He ran shell because it was cheaper. After like 20,000 miles or so, the engine needed a rebuild. Granted this was a long time ago and gas is more closely regulated.

Bobboloo · Bobboloo's Garage

Try filling up and not putting in the additive. The additive maybe part of the problem. From what I've read you don't need it and it maybe even be bad for your motor.

If your motor has stock compression then you don't need high octane. It will probably run better on regular. My understanding is that you match octane to the design of the motor. Running higher octane gives you no extra performance.

Of course this is an old subject that has been beat to death many times on this board.search the archives.

Bobby

pwd72s · 06-25-2002, 02:59 PM

Zendalar? Is your '72T still running a stock 2.4? If so, plain old 87 octane regular would do. If not stock, do you know your compression ratio?

RoninLB · 06-25-2002, 03:14 PM

Hate to be a party pooper...but, IMHO, do the routine fuel contaminent testing...maybe a bad load of crap/water, clogged gas filter, etc...IMO, eliminate the standard BS first..then get intellectual. Paul the Don doesn't give advise because he has nothing else to do, if he writes it, you believe it.........Ron [still in la la]

nostatic · nostatic's Garage

For you US boys, don't get too excited, as I suspect that is a RON figure:

Gasoline pumps typically post octane numbers as an average of two different values. Often you may see the octane rating quoted as (R+M)/2. One value is the research octane number (RON), which is determined with a test engine running at a low speed of 600 rpm. The other value is the motor octane number (MON), which is determined with a test engine running at a higher speed of 900 rpm. If, for example, a gasoline has an RON of 98 and a MON of 90, then the posted octane number would be the average of the two values or 94.

From http://chemistry.about.com/library/weekly/aa070401a.htm

pbs911 · pbs911's Garage

99 octane fuel

No wonder gas is $5.00 a gallon in Europe.

pwd72s · 06-25-2002, 06:00 PM

Quote:

Originally posted by RoninLB
Hate to be a party pooper...but, IMHO, do the routine fuel contaminent testing...maybe a bad load of crap/water, clogged gas filter, etc...IMO, eliminate the standard BS first..then get intellectual. Paul the Don doesn't give advise because he has nothing else to do, if he writes it, you believe it.........Ron [still in la la]

How could I disagree? This is a deal I can't refuse. LOL! Ron, you're probably right on...BAD GAS!

CamB · CamB's Garage

Quote:

Originally posted by nostatic
For you US boys, don't get too excited, as I suspect that is a RON figure:

Yep - the rest of the world (yes, there is a rest of the world) uses RON on the pump to state the octane level.

ChrisBennet · ChrisBennet's Garage

Quote:

Originally posted by paulhagedorn

I know Cali is screwed up and such, but what is the point in not having gas that is 92 or 93 octane. Is it that they dilute real gas with so much crap that it goes below 93 octane? Doesn't all gas start off at the same octane and is diluted to what the companies want along with the respective additives?

I don't think it works that way. AFIK, from a barrel of crude they get so much X octane and so much Y octane and on down the line until they reach tar.
-Chris

slakjaw · 06-26-2002, 06:42 AM

sounds like water in gas to me

Mikko Kosonen · 06:57 AM

EDIT: Zen=Mikko Kosonen

It sounds like it, but it is not possible. The place where the fuel line on my tank is connected is way upper than the regular fuel takeout place. I had the tank sandblasted last year and I changed the pipe placing. The popping is not cause of water unless there is about 5 litres of water in the tank.

Sometimes I put in tank this ethanol solution that is meant to be used in our climate: Prevents carburator freezing in near zero temperature and it also mixes with water therefore creating a flammable liquid that engine can burn just fine. So, it ain't water..wish it was.