1973 Super Beetle! What Gas To Use?
CENA
08-31-2007, 10:49 PM
My owners manual states I should use nothing lower than 91 octane. Now I don't know what the previous owners were using, but the last owner did fill up with regular unleaded. Octane 87. What do you think? Can I use 87? Will it hurt the motor? Thanks!
denisond3
09-04-2007, 02:13 PM
Will using 87 octane hurt the engine: No and Yes. If you hear pinging (detonation) - you should either use the higher octane fuel, or you should retard the ignition timing a couple of degrees and try listening again. Having the spark retarded will probably eliminate the detonation, but it might need to be retarded by more than 2 degrees. Up to 5 degrees of retardation is all it should take. And you may get slightly less miles per gallon, but it shouldnt be dramatic.
If you dont know what detonation sounds like, get someone to ride with you who does know, and listen for it. It will be a faint tinkling sound, almost like a telephone ringing in the neighbors house. It will happen when you are in high gear, going up a hill or trying to speed up, with the gas pedal down toward the floor. If its going to happen, I think it would happen in high gear between 35-65 mph. If you dont hear any detonation or pinging with 87 octane fuel, than you can safely use it.
By the way, detonation is more likely to happen when it is hot outside. It would be less of a problem in the winter, but can still happen.
Continued detonation will result in the pistons overheating at the top, and can allow the crown of the piston to begin melting, (this is called a burnt piston) and pieces flaking off. Engine failure will soon follow that.
Another cure, on long upgrades, is to downshift, and let the engine make a lot of cooling fan noise.
The noise a diesel engine makes is essentially a louder more steady version of 'detonation' in gasoline engines. In diesels it is how they run - so is normal.
If you dont know what detonation sounds like, get someone to ride with you who does know, and listen for it. It will be a faint tinkling sound, almost like a telephone ringing in the neighbors house. It will happen when you are in high gear, going up a hill or trying to speed up, with the gas pedal down toward the floor. If its going to happen, I think it would happen in high gear between 35-65 mph. If you dont hear any detonation or pinging with 87 octane fuel, than you can safely use it.
By the way, detonation is more likely to happen when it is hot outside. It would be less of a problem in the winter, but can still happen.
Continued detonation will result in the pistons overheating at the top, and can allow the crown of the piston to begin melting, (this is called a burnt piston) and pieces flaking off. Engine failure will soon follow that.
Another cure, on long upgrades, is to downshift, and let the engine make a lot of cooling fan noise.
The noise a diesel engine makes is essentially a louder more steady version of 'detonation' in gasoline engines. In diesels it is how they run - so is normal.
BoatCop
09-07-2007, 08:37 AM
Look at the manual again. And on the sticker on the inside of the gas door. I believe it says to use 91 RON gas. RON is a UK measurement. 91 RON is equal to 87 octane.
CENA
09-18-2007, 03:30 AM
Thank you for the info!!
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