Hello friends. Question, is it wrong to used Leaded Gas? The manual says use only unleaded. The car is an 87 model 760GLE. Someone said it could help in quick starts.

The higher octane fuels are all unleaded. You could try them and see if the car starts and runs better, no damage will be done except to your wallet. If your engine was pinging from predetonation, the higher octanes could help. If your engine is pinging, the knock sensor will be retarding the spark until the pinging is eliminated. You might not hear the pinging but the retarded spark timing would take away some power.

Leaded gas has numerous disadvantages: it will almost immediately ruin a catalytic converter; it will foul spark plugs and create combustion chamber deposits; it will load engine oil with additional deposits; and it is not good to breathe the exhaust fumes. It will not help in "quick starts". If you have a problem with the latter, then something is wrong with the engine and should be repaired.

I am certainly no authority here, but I see no reason to use leaded gas in your model car. I wonder if it would screw up the converter? Certainly, you would not pass emissions testing if you live in an area that requires that. Where can you even get leaded gas these days?!

I should have said, a higher octane gas. For example @Shell, theres Bronze,silver Gold. Id normally put Bronze(unleaded) and would harm the car if I put the Gold or Super Regular.

I recently did a test, one tank of regular, one tank of high octane.

Regular gas = 600Km to a tank
High Octane = 700Km to a tank