Well, you have to start your learning somewhere, this is a very basic question but yet so important :)

We drove home a -72 today, pictures and the whole story will come in next week when I've borrowed a digital camera.
But the tank is almost empty and tomorrow morning we want to take a tour and tank her, but suddenly we realized that we dont know what fuel she wants?
95, 98, with or without lead, any additions?

It is a -72, 350 original engine, tuned a little but I suppose that that doesn't affect the fuel needed when there are only basic changes made.

Thankful for any answers.
/Christian Larsson, Sweden


[Modified by Larsson, 11:45 AM 10/25/2003]

 

In Chicago, about the best we can do is 93 octane, unleaded. Runs fine once you get the timing dialed in. Good luck!

 

I only run 87 unleaded, Should we be running the most we can buy or is this sufficient for everyones needs? All the cars that my family owns say that the vehicle requires 87 octane.

 

Thanks for your answers, in sweden we have to choose between 95 and 98.
I went down to the car and found two flashes of "leadreplacementfluid" (directly translated from swedish, I don't know the correct english word but it's fluid that replaces the lead).

So I suppose that the last owner has used it with fuel additions.

The best seems to be calling the last owner so I know for sure, but keep posting what you uses and think I should use.

 

i always use premium fuel is better refined becarefull with lead subuite
is very harmful to you if you get any on you
doc mow

 

I dont know why you would want to run it with leaded fuel. As far as the choices I would go with the highest grade. I dont think the lower grade will stop your car from running or anything either. Like they said higher grade is more refined and will help with keeping things regular, consitent, and clean.

I also only like certain gas stations around for that type of thing although I dont know how applicable that is to you. But I think another key factor is whatever you decide to go with keep with it. It will also help if your car starts sputtering and whatnot you may not have to second guess the gas (although it could happen even from the same place).

Good that your asking maybe someone else can give you a better scoop on gas. TTT!

Spook
:reddevil

 

You won't do any harm by running TOO MUCH octane, just wasting money. Try the highest level that you can get, then experiment with lower octane until you hear knocking/pinging under load. Move back up one grade. Running higher octane than neccessary has no beneficial effects, but you'll find that there's all sorts of urban legends about the supposed magical power of high octane gas. All :bs

The car was built at the factory to run on unleaded fuel, so there's no need to add lead (more waste). Even Corvettes that were built for leaded fuel suffer no real adverse effects while running on unleaded fuel unless there being used as a towing vehicle up steep grades.

:chevy

 

95 octane is an over kill in my opinion. :skep:

 

I agree with the "start with the lowest" octane logic. I've run 87 octane in my '77 L48 since I've had it with no problems.

"The car was built at the factory to run on unleaded fuel" -- Just curious what your source is for this. Not doubting you, but the only information I could find that stated anything specific about unleaded fuel was for the '71 LS6 (no other engines that year) and everything since '73.

 

'72's were made to run on unleaded fuel. GM started to use hardened exhaust valve seats in the '71 model year knowing that unleaded fuel was on its way. Running on 95 octane should be more than sufficient. I believe in Europe, your gas is based on "Research Octane" where in the US it is based on the average of Research and Motoring Octane. I know that 98 "Research" is equivalant to about 92 (R+M) so you should be OK. It's never good to run too low an octane number because of the potential damage due to spark knock, but running excessive octane just means your spending more $$ than you really need to.

 

"Even Corvettes that were built for leaded fuel suffer no real adverse effects while running on unleaded fuel unless there being used as a towing vehicle up steep grades."

Actually, this is NOT correct. Vehicles made PRIOR to 1970 are NOT recommended for unleaded fuel unless a lead substitute is used or a valve job is done. The lead acted as a cushion on the valves on these cars and using unleaded fuel can cause some major valve failures. New valves are hardened and have hardened seats.
Also, the octane from unleaded gas may not be sufficient for the truly high performance engines of 11-1 compression or higher.

Dep

 

Actually, this is NOT correct. Vehicles made PRIOR to 1970 are NOT recommended for unleaded fuel unless a lead substitute is used or a valve job is done. The lead acted as a cushion on the valves on these cars and using unleaded fuel can cause some major valve failures. New valves are hardened and have hardened seats.
Also, the octane from unleaded gas may not be sufficient for the truly high performance engines of 11-1 compression or higher.

Thanks for all your answers while I've been sleeping :rolleyes:

What made me nervous is what stood on the flashes with leadadditions I found in the car, something about that running an engine that wants lead without lead for 60 hours would destroy it.
I will call the last owner today to make sure what he used, maybe he drove with 95 octane and added a little lead in special intervalls to make sure nothing happened to the engine?

 

As others have said...with a'72 you should be okay. If you have a 1970 or earlier that hasn't had a valve job since the engine was built, then you would need to use a lead additive.

Dep

 

You're right Dep, that was the thinking back in the '70s and '80s about using unleaded fuel in older engines. Actual experience in the last twenty odd years has shown that the fears were gradually exaggerated and there's little or nothing to worry about. As I said earlier, there's lots of myths about gasoline, this is one of them.

Do you personally know of anyone that has burned an engine because of this? No, neither do I. :cheers:

Besides that, the so called 'lead additives' are pretty ineffective in being a lead substitute.

 

87 causes my engine to ping when stepping on the gas hard at 35 in 4th. I went up to 89 and now it dosen't.

 

Do you personally know of anyone that has burned an engine because of this?

As a matter of fact...YES! Quite a few of them. Although not in Vettes. I also own two Harleys and the early Shovelheads (1965-1975) all had problems with valves and seats cracking because of unleaded gas. One of the major selling points on a used Shovel is whether it's been "converted" for no-lead gas use (new stainless valves and hardened seats).

I don't know a whole lot of people who own pre-70 cars, so I can't really give accurate data on that. But remember also that a large percentage of pre-70 cars have HAD valve jobs and made the changeover to unleaded-style valves and seats. Think about it....if unleaded gas DIDN'T affect leaded-style valves and seats, WHY would they make the new heads or rebuild old ones so that they would be safe to use with leaded gas????? :D
Some "myths" have a REAL foundation in fact :)

Dep




[Modified by Dep, 9:46 AM 10/25/2003]

 

Now I feel really split but keep the answers coming :)

I spoke with the owner two steps back that has rebuilt and tuned the engine and he said that he used to tank 98 octane and pour some lead addition into the tank. But he had also heard from some people that he should be able to run on normal 95 octane.
We read on the gas station near where we live
"96 octane, no need for any lead additions" (translated from swedish), same for 98 octane.

Suppose that we'll start with the 98 octane that already at the gas station had some kind of lead addition in it. The car will run at most 1000 miles per summer so it might not be any huge problem...


[Modified by Larsson, 11:45 AM 10/25/2003]

 

Have heard conflicting info on whether an lead additive is really necessary but seeing how you are running only 1000 miles or so a year it couldn't hurt and wouldn't cost much.

 

Larsson: QUIT WORRYING!!! The '72 Vette can run on unleaded gas just fine!!!
It even says so in my owners manual. It's the Vettes made PRIOR to 1971 that might be of concern.

Fevre: BTW.....mileage has nothing to do with the danger to the valves/seats. You could drive zero miles all year and have a problem just running the engine at idle if you have a pre-71 Vette.
You really ARE trying to up that post count aren't you? ;)
Are those little stars THAT addictive??? :D :D :D

Dep

 

I agree with Dep. Your car was built at the factory to run on unleaded fuel without concern.

The argument about lead/no lead can go on forever without resolution. It is true that some engines DID suffer from valve and seat degredation , but as I originally posted, this proved in the last 20 or so years not to apply to Corvettes. My comments were intended to be limited to Corvette engines, or Chevrolet passenger cars in general. A discussion of AMF Harleys, lawn mowers, garbage trucks, farm tractors or other closely related vehicles is another kettle of fish. All of these tended to burn valve with or without lead anyway.

The key to burning valves (or not) is metal temperatures at the valve/seat interface. If the engine exhaust temperature is hot enough that the metal is approaching it's melting point, the lack of lead coating will allow temporary microwelding between the valve face and the seat. This tiny weld is broken loose the next time the valve opens, with some material transferred from one face to the other as a result. This process will repeat itself until the two faces are heavily eroded and an effective seal cannot be maintained. This is why only exhaust valves are affected by this, and not intake.

In the case of Corvette engines, since they rarely (if ever), attain the critical temperature, no microwelding occurs. Nobody pulls trailers over the Rockies with a Corvette, do they? :crazy:

My local club has a majority of pre-70s cars in it. Not one has ever burned a valve since unleaded fuel came out, and not one uses an additive of any type.

Hope this helps allay your fears. :thumbs:

There's a string on this subject over on the NCRS board if you would like more info
http://www.ncrs.org/forum/tech.cgi/read/100615

:cheers: