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Triumph TR6 - Unleaded fuel for UK TR6s

Has anyone had experience with metering unit problems on fuel injected cars as a result of using unleaded fuel? Having just bought a 1972 150bhp TR6 I am somewhat surprised to learn that the seals in the metering units are not compatible with unleaded fuel. This surprises me; I wouldn't expect the difference in the fuel to be responsible for this type of problem. It is highly unlikely that the lead compound (lead tetraethyl) to contribute any lubricant property to leaded fuel; this I don't believe. Whilst the problems with valve seat wear is well-documented, and the role of lead oxide in helping prevent this is well understood, I remain unconvinced that the lead compound present in unburnt fuel can have any benefit whatsoever to the metering unit or fuel pump. I have been warned that the use of unleaded fuel could potentially cause the metering unit to seize!

I would like to hear from anyone who has experiences of problems, or who has successfully used unleaded fuel in their TR6 without mods to the fuel pump or metering unit.

Paul Walker
West Yorks
Paul Walker

Hi Paul,

You have seen my thread regarding my TR6 running badly. This is all since I put an unleaded head on the car and started using unleaded. The problems started basically imediately after using the unleaded fuel (Always difficult to link totally to the fuel because in the process of changing the head you could have messed anything up.!!)

I am wondering whether this is the problem but am not sure how to check. If you know, can you respond.


Adrian Gould


I am surprised by that assesment. In Canada we have unleaded fuel mandatory since mid-80's. Unfortunately we do not have P.I. TR6 here. But my experience with two cars Volvo with k-jetronic and L-jetronic, I did not notice any problem with P.I. after the switch from leaded to unleaded.
Fuel has never been a lubricant, usually you could used it to clean parts full of grease, no matter that it is leaded or unleaded. And seals will not be protected by leaded but they are built to resist to aromatic molecules of gazoline. Lead has been known to protect valve seat from recess acting like a lubricant or a coating. I run my TR6(carb)for 15 years with unleaded and it is the first time this year that a valve job was a good idea and no valves were burnt. I drive around 6,000 miles/year, this mean that recession caused by unleaded is a scarecrow (I check valves adjustment every 3,000 miles). The only drawback as far as I remember is that leaded gas had a better octane rating and behavior. This mean that you must play with your advance mechanism. Best luck.

Cheers, J.G.Catford, Québec under the rain, Canada
Jean G. Catford

This thread was discussed between 09/08/2000 and 15/09/2000

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