dingusboy

I have reviewed prior posts, but do not see a consensus on fuel additives for pre 71 cars. What additives are you using to compensate for unleaded fuel? Are you using substitutes or adding lead? Any and all opinions welcome.

csstrux

The recurring comment I have seen is that the seats have a high enough nickle content to survive using the unleaded gas. I am not an expert, but from what I have read, and from personal experience, in unmodified cars, I would not worry about it. Most of it seems to be snake oil any way from the bit of reading I have done on the topic. If others have found, or are using a good product they will chime in.

Steeb

I always use the highest octane, and just recently started throwing in a bottle of Marvel Mystery oil.

J-(Chicago)

I use 93 with lead additive.
What Chicago suburb are you in?
If you're near a Meijer grocery store they usually have huge bottles of it for cheap because no one ever buys it.
Chances are your heads will be ok, but since they're not making any more heads, and they're not getting cheaper, I like the added insurance that I'm not beating on my seats. I beat the snot out of my car fairly often.

Olds64

If you rebuild the heads make sure you use hardened valve seats.

fatboy578

I have a 69 442 ,and I always use a lead substitute,plus once in awhile I throw in a bottle of octane booster. I always use premium. Personally, I have noticed a difference in the way my car runs. I have read that unless the valves have been replaced, then an additive should be used.

dingusboy

J-I live in the LaGrange area. I am trying not to rebuild yet. If I do, I will use the hardened valve seats. I'm afraid of any product that claims to be a "mystery". Their web site says that it is a cleaning agent and not a lead additive or substitute. Steeb-Are you using it as a lead replacement? Here are the things that I have found on the net. You tell me, fact or fiction.

- Pre 71 vehicles need Octane nearing 110.
- Additives like Gunk just replace the protection to the valve seats and do not raise the octane.
- Actual lead repacement would increase the octane, but there are no readily obtainable supplies.

68Tom

I too found that my car ran like crap without the substitute for some reason. My engine will now have the hardened seats, so I won't need the lead, but I used this prior to. It's easy to store, and a bottle lasts something like 3000 miles. Much better than the stuff you typically find at the auto parts store (one bottle per tank).
http://www.midwayautosupply.com/p-21...oz-4295-6.aspx

Eddie Hansen

I will only venture a comment on this one... it's crap...

when I was a kid many many moons ago, (1972) my first job was pumping gas @ Sunoco you gould get 260 gas which at the time was 100 octane I did "Hear" about 280 never saw it this was suppose to be 102 octane stuff and then there was Cam 2 racing gas which was 104 octane...

110 must be like avgas, ( which we could get down at the airport)
now there was some crazy compression ratio and I have seen a car with 13.5 to 1 run on the 260 gas without problems.... but remember it was a long time ago, Oldsmobiles regularly came with 10.5 to 1 right? man those were the days and I was pumping it at around 42 cents a gallon LOL....

jensenracing77

the additives do not change the octane to any noticeable difference. the goal is to lubricate the valve seats. to do this all you need to do is add about 1/4 quart of ATF to each tank of gas. if you have pinging or detonation then this is another issue than the valve seats and yes you will have to increase your octane to fix it. if you are driving a diesel of anything older than 2008 i would add 1/2 quart of ATF to your tank of fuel (this has to do with the injection pump not the seats). when you have the injection pump rebuilt make sure that it is upgraded to accept the dryer fuel that we have today. i am no expert but do have just a little knowledge of the subject. and Marvel Mystery oil will work also for the valve seats but ATF is cheaper

Olds64

An additive they are using today that significantly changes octane is ethanol. Of course, that is another can of worms.

I usually use a quart of Marvel Mystery Oil or Risilone once a year. Once I start the new engine I think I am going to use Rotella T in it. The diesel grade oil is supposed to cut down on sludge and carbon alot easier than the normal stuff.

bigoldscruiser

I, too, use Marvel Mystery Oil. It is recommended by the National Buick club and also by Joe Mondello. There is a lot of talk but I have seen no real proof that seat protection is required. Many owners back in the 50's and 60's used Amoco white gas - NO LEAD - and some of us are still driving those cars today. Just do what makes you feel the most comfort.

jensenracing77

olds64, you are right in the rotella T. it is a good choice for our flat tappet cams also. i now use Mobil 1 in all my cars now but it is a little expensive. it's not that much more than rotella T.

88 coupe

None. Unless an engine is under constant heavy loads, lead additive is a waste of money.

Norm

Redog

I was using Gunk Lead Additive in my motor.

I was doing it every other tank, but it would take a month to run the tank dry, so I just did it every tank.

The last fill up on 9-11-08 was $86 plus $3 for lead additive. That motor only liked the 93 octane. I tried 91 once and I got 5 MPG compared to the usual 13

9-12-08 was the worst day I'm still pissed at that kid

dingusboy

Thanks all for your input. Here's my plan. I will probably use Marvel Mystery Oil being overly overcautious to maintain valve seats. If I notice rough running, I may try Lead Max 2000. Obviously, always use highest octane.

Bluevista

I know a real lot of guys that swear by Max Lead 2000 real tetraethyl lead additive and buy it by the gallon. I got a quart from a buddy and tried some in my goat and it really makes no noticeable performance difference but maybe it helps internally?
I usually don't use anything but Shell premium and don't beat on it...too much.

http://maxlead2000.com/

citcapp

I ran my olds 371 J2 on unleaded premium gas for eight years and when I yanked the engine to install the 455 it still ran fine. I sold it to a guy who is installing it in a 47 Olds without doing anything to it. No harm done