Lead fuel additive

[Vifa]

Hi,

A simply question about lead fuel additive. I just realised I have done it wrong for the last 1500 miles. I have added lead fuel additive AFTER filling up the car with fuel.

I just read on the bottle that it should be done prior to refueling the car.

Should I worry about anything ?

[Matt Harwood]

No.

 

Lead additive is a myth anyway. If you don't need the octane, your car isn't going to miss the lead. The whole thing about cushioning the valve seats and stuff like that is an old mechanic's tale. Lead was added to boost octane in the 1950s and everyone kind of assumed that their cars needed it. No need to waste money on it (especially since today's "lead substitutes" contain exactly 0 lead) but if it brings you peace of mind to use it, I think you will do no damage adding it after you fill up the tank.

[61polara]

Nothing to worry about other than you may be wasting money.  If you pour the additive in first, the gas you add will flush it down the pipe and you have extra turbulence in the tank to mix it.  Adding it after you fill the tank, because you are driving the car out of there and sloshing it around that way.  You may not even need a lead additive if your car ever ran on leaded gas or has hardened valve seats.  Lead additives were the snake oil of the '70's.  Everyone thought their valves were going to be destroyed in short order when lead was eliminated.  In the 40 years since, I've never known of a valve job being done because there was no lead in the gas.

[Vifa]

Good to know - thanks for the anwers ! ;-)

[Rusty_OToole]

There were problems with valve recession after lead was phased out especially on Chevs. I don't know if it was the lead, or the lean mixtures required for smog control.

 

Cars from before about 1955, and after 1970, are made to run on low lead or no lead fuel. High performance cars 1955 - 1970 with compression above 9.5:1 MAY need octane boost (some do some don't).

 

If you want to baby your valves, rings, and upper cylinders you can add some Marvel Mystery Oil, Redex, 2 stroke oil or your favorite additive but it is not strictly necessary.

[Guest johnjackson]

Rust hit the nail on the head or nailhead if you drive a Buick.

[64Riv-King]

Or you can take a couple 5 gallon gas cans to the nearest airport and get 100 octane low lead AV fuel. 

[Stude Light]

The lead additives they sell do not contain the tetraethyl lead that was used back in the day. The Avgas does, but I'm with the rest of the crowd......unless you are running extreme combustion temperatures along with high valve seat pressures, don't waste your money.

[Guest Bob Call]

Unless you have a car built after WWII your car was designed to run on a diet of unleaded 60 octane "white gas" until leaded became common after WWII. All of these fuel additives on the market are only good for the guys selling them. Save your money.

[cahartley]

I still think any additive that will impart at least a modicum of lubricity to "dry" ethanol gas is worth using.

ANY lubrication is better than none.

[Guest Jeff k]

My Pontiac 389 and 455 both ran better on unleaded once tuned for it... My 1964 389 had over 150,000 miles on the heads run on no lead with no issues... Remember Ammco Gold?

 

Frankly, I think todays fuel is better then the old leaded fuel, at least the stuff we get around here in Western Pa is.. When was the last time you had to change plugs or blow out the motor on the highway because of lead fouling...

 

I noticed todays fuel seems to run best without the intake heated and with a fuel return line back to the tank... Other peoples experience might be different.. I do use a custom Quadrajet built by Cliff Ruggles..

[Spinneyhill]

I think all fuels run better without the intake heated. You get more oxygen in the mix. Heated air expands, meaning less air in the same volume. As for the fuel itself, the higher octanes today usually mean more aromatics that vaporise readily, but it also burns more slowly than the old low octane petrol did. It is probably not so good in side valve engines: the flame front might not get right across the chamber during the highest-efficiency part of the stroke.

[Restorer32]

You wonder how Amoco maintained their market for Super Premium since it never had lead.

[Guest johnjackson]

Ethanol does burn cooler but dryer, at least a basic lead additive will allow valve seats to have some protection which is better than none.

[ArticiferTom]

There must be something to lead TEL in fuel . As EPA is in middle of big evaluation to pick a replacement for LL and VLL avgas fuels used in piston driven planes .  There are 5 companies vialing for certification as all TEL will be gone from fuel after 2016 if substitute is found . There are no more manufactures of TEL in US only UK as one left .

    So high performance guy better buy and store . An article can be found about it online search EPA and leaded gas .

[Guest Bob Call]

Most of the fuel additives sold as lead or octane boosters are mostly alcohol. The clean air laws prohibit the use of lead in about any form except solder. If you want an "upper cylinder lube" put a little diesel, MMO, motor oil, in your tank after fill up. Putting it in first if the tank is really empty it will settle in or around the pick up. Putting in after will mix with all the fuel with normal motion of the car.

[Guest]

We all know lead was used as a octaine booster.  Tetraethyl leads other job is to work as a buffer against microwelds forming between the hot exhaust valves and their valve seats. Once these valves reopen, the microwelds pull apart and leave the valves with a rough surface that would abrade the seats, leading to valve recession. When lead began to be phased out of motor fuel, the automotive industry began specifying hardened valve seats and upgraded exhaust valve materials to prevent valve recession without lead. If you drive a vehicle conservativly that doesn't have hardened seats and valves you will not have any problems, however if you sometimes use your car for drag racing or more importantly for road racing or grand touring you are only asking for valve/seat problems even if you are using lead free racing fuel.

I just checked with the track where I used to race, they still sell 110 octaine leaded racing fuel

Edited December 19, 2015 by helfen (see edit history)

[Spinneyhill]

Someone above said they had never seen receding valve seats. When leaded fuel was stopped here there was a rash of head jobs on receding valve seats. The worst were hydraulic lifter engines. You didn't know until it developed asthma. The same thing occurred with a lot of engines converted to run on LPG

 

BTW, TEL was developed in the 1850s and used from the 1920s.

[Rusty_OToole]

There was a rash of  valve seat recession especially on Chev V8s. I'm not sure if it was the lead or ultra lean mixtures needed to pass emissions tests.

[ply33]

Original posted does not list the car, but some makes actually had hardened exhaust valve seats and special alloy exhaust valves from the '30s into the late 50s. Use of any additive to "lubricate" the valves on those cars is really a waste of money. Any gas with high enough octane (above maybe a 65 or 70 pump octane rating for the '30s cars and maybe low 80s pump octane for the 50 cars) is sufficient assuming running stock compression.

 

I guess there are a bunch of people running mid-century muscle cars out there based on all the recommendations I read about running 100 or 110 octane AV gas. Sounds like an inconvenient, expensive and unnecessary thing to do unless you have some rather exotic vehicle.

 

I worry more about getting a fuel system component that was manufactured or rebuilt with parts that are not compatible with modern fuel additives. Fuel pump diaphragms, flex hoses, etc. made before maybe 1990 are in my mind suspect and I'll use modern kits to rebuild them before I use them on my car.