Hi I have a 1969 Cadillac Coupe de Ville with 39,000 miles. I always use premium gas. My question is do I need to use a lead additive when I put gas in? Thanks Gene
I would be using a lead additive just as a precaution.
Especially without knowing the condition of the valve seats.
Bruce. >:D
Thanks Bruce for the advice.
Yes, you need the lead additive if you are not 100% that the valve seats have been replaced by hardened valve seats. Only the cars that use unleaded fuel from the factory (I believe this was introduced somewhere in the mid seventies) can use the unleaded gas from today. I use an additive in all my old cars.
Caution: always use the same additive. I am not sure, but I've heard from others that mixing additives from different brands can cause a chemical reaction in the gas tank. Although it might be complete nonsense, I decided that I did not want to find out the hard way and always buy the same additive.
The '71 and on were designed for Unleaded.
Bruce. >:D
You rarely see or hear about valve seat issues in the 472-500 engines. One reason is they don't tend to get pushed real hard like they would have if they came in say a Charger or Camaro. The other reason is I suspect Cadillac used higher nickel castings than your typical Ford or Chev motor so even if they got pushed hard (or didn't have lead) they would wear better.
I think even in 69 the Cadillac manuals said you could run the new 'low lead' fuels.
Quote from: genecado on April 21, 2017, 09:45:36 PM
Hi I have a 1969 Cadillac Coupe de Ville with 39,000 miles. I always use premium gas. My question is do I need to use a lead additive when I put gas in? Thanks Gene
Gene,
I've never, ever added lead in any of my cars and they're all pre-73. Have pulled many heads and have never seen problems. But then again, I don't drive like a Cowboy.....
Bobby
Agree, have never used the stuff in any of the '60s Cadillacs (4) I have owned over the years and have never seen the need to do so.
In 1963 the Engineers at Cadillac (they had their own engineering division then) knew that to meet the pending polution regulations gasoline was going to have to have the lead removed. Everything from 1965 on was designed to operate on unleaded gas and all provisions were made in materials and construction of the motors to do so. The major drawback of using unleaded gosoline in your car will be the lack of lead deposits on the spark plugs and the cleaner cylinders and valves.
My '66 went several hundred thousand miles without ever tasting lead and since I have a heavy foot it was driven as hard as any Camero or Charger.
Greg Surfas
Back in the day, (at least the '60's), Amoco sold lead free gas, although my childhood recollection is that it was high octane. So maybe lead is not that critical as long as the octane is "up there."
The Kid is a leadfoot. So am I. David is 100% right about octane in the old 10:1 and 10.5:1 compression engines. I had a '70 CDV which I drove to L.A. once , and gave it a treat of 100 or 110 octane gasoline. There were a sufficient amount of stations where you could get that juice. Expensive , at a time when pump gas was under a buck , this stuff was $5 ! But I'm here to tell you , that '70 and my foot sure liked the treat ! DO NOT PUSH YOUR HIGH COMPRESSION CADS HARD ON MODERN 91 - 93 OCTANE PUMP GASOLINE !!! Detonation occurs before you can hear knock. Knock , or "pinging" is not detonation. It is called SEVERE DETONATION. Back off that throttle. Hmmmm , is it deja vu ? Seems I have said this before. I don't know , but I guess it was worth repeating anyway. Did I mention that you could get gasoline up to 129 octane back then ? Probably still can. How else could those multi-billionaires scoot about in their 13:1 "antique" racing Ferraris and the like ? I never had to look into the price those fortunate few had to pay for 129. Speed kills. Enjoy it only in apropriate places and conditions. - CC
I want to thank everybody for your opinions. I have heard that using unleaded gas is ok as long as you don't push your engine hard.
Like marine service or racing.
Seem to be missing the point. Tetra Ethyl Lead was added to gasoline to increase the octane rating. When lead was slated to be removed from motor fuel, other octane enhancements were developed. I run VP MS-109 in my quarter mile cadillac. It is unleaded, and as the name implies is 109 Octane. Only $11.50 per gallon, so it is mixed 50/50 with 93 octane Chevron. No Lead, no knock.
Greg Surfas