I've read mixed opinions on whether a lead additive should be used when fueling up most classic cars. I have a 68 GS400 (all original). I run 87 octane fuel, but have never used the additive. The car runs well overall, but I sense some sluggishness at times. I inherited the car about 3 years ago, and since have put about 1,200 miles on it. 56k miles overall. Appreciate any feedback/guidance on whether I should be using an additive.
Funny story, went to the local orileys to buy some oil. The manager is a car guy and chatted me up about my 65. He tried selling me into a lead additive. The classic sales pitch of me needing it ect ect. He read me the entire bottle but it didn't provide much info. So he pulled up a random website that reviewed it and it pretty much concluded with its not neccessary at all. Let him speechless and me holding in my laughter.
Your car should not be run on 87 octane. You probably drive it pretty easy, so you may be getting away with it. Valve recession is more likely under high load conditions. That car should not be sluggish at all. The ignition timing is probably off which would explain the sluggish performance and the engine running with no audible ping? Have you owned the car from new? How do you know it's all original?
Thanks for all the comments. I'll definitely start running with 93 octane. Larry - appreciate the guidance and questions... I'm still learning about the car. My wife and I inherited it 3 years ago from my father-in-law, who was the original owner. We've been together for 35 years, so I've been around the car regularly for that long. Prior to that, after 5-8 years of regular use, it sat. So, while I can't be absolutely sure it's original (though my novice lenses), I have a high degree of confidence it is. By the way, if you knew my father-in-law (lazy , cheap, and never took care of anything), you would understand why I'm even more certain it's original.
Check the distributor part number. It should be 1111335. The part number is stamped into the circumference of the distributor. As an example,
That car is pretty high compression 10:1? 10.5:1? and used "high test" from the factory. It really likes the highest octane you can feed it. I am amazed that it isn't pinging like crazy on 87?
Mine ping on 93 without retarding timing. The ethanol fuel also runs leaner as well. I had to run 87 in my Riv GS one time on a trip and the spark knock on startup alone was horrible. Ended up turning the distributor just so I could make it over the mountains without death rattle.
Mine likes the ethanol free (90 octane here) the best, although my engine is not exactly high performance.
It's probably the original 1968 1111285 since the 285 is visible. The ones are probably to the left in the photo and the numbers to the right are build date codes. You are getting good advice on using 93 octane gas. It should improve your performance. You could also increase the initial timing a degree or two if you have a timing light. No need for lead additives or octane boosters.
Thanks for the all the guidance. I did find the number: 1111285. It was on the other side of the distributor. Sorry, I couldn't get a good photo, but will try again later.
My 68 GS400 (93,000 miles, original engine, not rebuilt) would ping with 93 octane unless I retarded the timing. I started mixing 5 gallons of 100 octane LL in each tank of gas and it ran much better.
I've been running a mixture of 93 octane and 100 LL. Luckily, there's a small airport 5 minutes from me and AvGas is readily available. Plus, there's nothing like that exhaust smell of higher octane fuel.
