Unleaded gas with or without lead additive?


Sharpest Tool
Feb 6, 2010
Ann Arbor MI.
First Name
Willys Model
  1. Wagon
Willys Year:
  1. 1961
I was wondering what people run in their wagons that have original power. I have a 226 and not sure if I should be running lead additive in the gas? I've heard that with low miles being put on these old, tough flatheads, that it won't really hurt the engine to just run straight unleaded. What are your thoughts and experiences?
My thoughts are that you should use it about every third or fourth tank full of gas if you don't have hardened valve seats installed.
Reason1: The original valve seats are an integral "soft" metal. More than likely the valves have not been adjusted as often as they should have and seating issues occur. This can cause hot spots, pitting, coking around the seat and so on. As the seat wears, compression is lost because now the valves don't seal when closed.

Reason 2: If the engine has been running since the loss of leaded fuels, one could probably say; hell, it's ran this long and it's still good; why bother?? My answer is; better to error on the side of conservativeness and prevention. Maybe you can get a whole lot more miles out of her if you start some regular care and maintenance practices. Orrrrrrr, you could just let it go and see how far you can get.

Reason 3: Yes these are tough old engines, however: An ounce of additive every 3 or 4 tank fulls isn't much, but it could pay off in the long run. It all comes down to your comfort level.
I would use the additives to provide lubrication to the valves. The old engines were designed for lead to lubricate the valve. It is easy to do and cheap piece of mind.
My 6-230 OHC was last rebuilt in 1978 by the tag on the engine. I doubt they put in hardened seats then, so I add lead substitute every third time I add gas.
lead additives on old engines are ok but, the new oil has teflon and some have zink to aid in lubrication. HOWEVER, on a total rebuild, valve guides, valves, valve seats and piston rings, better to leave the additive in the store and go with the modern oil for lubrication.

Now I know there are a lot of "experts" here but, not only am I an automotive engine rebuilder, I also hold an FAA mechanics license and know a lot of information on small aircraft engines, over 35 years worth. The Continental, Licoming, Hurricanes and Super Hurricanes are one of my specialties.

Oil and Gas additives rarely do what they bost on the comercials and on their label! BEWARE! Gas Additives like Barryman's B-12 helps reduce H2O in the tank and burns clean. Lucas gas additive is a mixture of diesel and oil, also good for the tank but, does not mix with H2O well.

I use Lucas when rebuilding engines because it's thicker than 30 weight and thiner than 80-90 weight. It hold in place for bearings and rings till engine startup with 30 weight oil.

Other additives like STP, Slick 50 Bardahal's just to mention a few are thined COAL OIL and KEROSENE. other additives are VEGETABLE OIL and will not mix well with gas or oil (might as well pour synthetic oil) in the tank or crankcase.

as soon as I find some of my aircraft records I will have Pete post the entire contients in PDF which shows what I'm talking about.

I hope this helps and I know someone out there will arbitrate what I am saying, but the proof will be in the PDF when posted.

, the new oil has teflon and some have zink to aid in lubrication
Zinc (ZDDP) was first added to motor oil around 1940 and has been in oil until the last 5 years or so when the amount of zinc was greatly reduced to prevent fouling of catalytic convertors.The lack of zinc is an issue with flat tappet cam wear on performance engines that is well documented ..Some speciality oils still have high levels of zinc.
Lead or Tetraethyl was used used as an octane booster since the mid 1920's but then found to extent exhaust valve life.It's not so much a lubricant as an aid to help heat transfer from the hot exhaust valve to the valve seat everytime time the valve closes.Under high load the exhaust valve can run red hot,without lead,each time the valve closes,it "micro welds" to the seat.This causes valve seat errosion over time. Most vintage engines aren't run hard so there's not enough seat wear to worry about.replacing valve seats isn't very expensive so it's a good thing to do during a rebuild.
If you want real tetraethyl lead ,you can still buy it. here's one place http://www.hi-flow.com/HPOP4.HTM It is expensive,I have used it in performance engines.