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1975 MGB require Lead additive?


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Unleaded gas was introduced in 1973 to protect catalytic converters. Your car is newer than that, so unleaded was on the market when it was sold and it is likely it was designed for it.

 

If your car was equipped with a catalytic converter, it probably requires unleaded gas. Does your fuel filler have a block off with a small diameter hole for the fuel hose nozzle to go in (just like all current production gas powered cars in the US)? That is designed that way to block the filling with the older leaded gas nozzles which had a larger diameter spout. If the filler opening is designed that way then your car was required to use unleaded gas.

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Thank you for your help. The fuel filler opening is designed to permit larger fuel spouts. There is no restriction. Therefore I suspect that lead may be a requirement. Before this car was shut down for several years I always added lead to the gas per the previous owners advice. But as i am restoring this car I am finding that the previous owner was not alway correct in what he did which gives me pause to believe his suggestion was on target. Thus my question. I will be a happy person to know whether or not this car actually requires lead additive.  Again thanks!

 

Jerry

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The leaded fuel crisis has turned out to be a non-issue for most old cars. Lead was mostly added as a cheap octane enhancer (pioneered by Charles Kettering, who also invented the self-starter for Cadillac) in the early 1950s when compression ratios were skyrocketing. Prior to that, unleaded fuel is what was available and what cars used. The 'valve cushioning' effect is purely anecdotal and was an argument that was used when the leaded gas was being phased out. When your car was built in 1975, unleaded gas was increasingly common and I doubt that an MGB has compression ratios that need the octane boost, so it was designed to run on unleaded without problems. Lead additives can bring peace of mind (they actually contain 0.0% tetraethyl lead), but what they really do is empty your wallet unnecessarily. I would skip the additive and run it on 87 or 89 octane regular gas and you should have no problems at all. The ethanol in today's unleaded fuels isn't good for any old car's fuel system, but if you're restoring the fuel system, use ethanol-friendly hoses and diaphragms in the fuel pump and carburetor, and you'll be ahead of the game.

 

Hope this helps.

Edited by Matt Harwood (see edit history)
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On 4/11/2016 at 3:58 PM, Jerry Alexander said:

I have a 1975 MGB and need to know if I need to add lead additive to the gas when i fill the tank.

 

Thanks for your help.

 

 

The 1975 MGB was the first year for rubber bumpers and the single carburetor, so it does not have the zip of the earlier years. It also came ready to run unleaded and California cars came with catalytic converters that were a real fire hazard. From 76 through 80 all MG's came with the catalytic converter and don't worry about having to pay extra for premium unleaded gas, when you get an owners manual you will see that the octane requirement is 87, which on this side of the pond is regular unleaded.  

 

 

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Wife and I ran 2 MGBs as daily drivers for several years back in the 1970s early 1980s. We virtually never used leaded gas since we found that Amoco Premium gave us the best mileage (probably a placebo effect)  and it never had lead. No need for any lead substitute in an MGB.

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I'm a little late chiming in here but agree the Lead Additives are not necessary.  We run the pants off our MGBGT and never had an issue with valve seat recession, which is what some recommend using the lead additives for.  We've also been told it's good to add when breaking in a new engine to help cushion valve stems, lifters, etc until broken in.   We followed MGB Experience Forum advice and used Shell Rotella motor oil at first as it contained the right quantity of lead in it.  Now we run regular Castrol motor oil.   You didn't indicate where you are located Jerry, we're in Southeastern VA (Tidewater area) and have a lot of MG folks in our AACA Region, as well as our local MG Club.  We are very active with both of them and enjoy either out MGBGT or the 1948 MGTC regularly.   Check our Tidewater Region's link on the AACA website, or our MG club at www.mg.org.

If you are in the neighborhood come on out an join the fun.

Terry

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Thanks, Terry.  I do appreciate your assistance and guidance.  I am located in western Illinois so I doubt that I will be driving to your area any time soon. If I ever do i will be sure to contact ahead of time to check in.  In this area of Illinois there are no clubs/organizations that associate with AACA, HCCA or any other national group. There are a couple of local clubs but they are either hot rod or muscle car emphasis. The MGB does not qualify as either, nor does my 1915 Metz or 1929 Chevrolet. But I still have fun with these autos and would not trade them for anything. Again, thank you for your help and the invite. All very much appreciated.

 

Jerry

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