Questions and Answers
Sentra Octane Requirements
Q. Recently I bought a used 1993 Nissan Sentra XE with automatic transmission about 123,500 milage. After few days it started knocking slightly when accelerating only when engine is warm. It does not knock on cold engine.
I found some information on internet. It says it might be because of either lower grade gas used, knocking sensor failure or timing chance is too advanced. I only remember that last time I put lower grade gas 89 octane and car manual says 87AKI (91 octane number) which still I could not figure it out that if I put in wrong gas. I purchased octane booster fluid to stop knocking but i have not added yet with this lower grade gas.
1. Did I put wrong/lower grade gas (89 octane) into my car?
2. Could you tell what the exact problem is?
3. That's knocking is harmful if I am running car with this type of gas?
4. Gas tank is now half-full of 89 octane grade gas and I am waiting until it is empty and I put in a right gas (91 octane). Do you think I should mix that booster fluid now with half-empty tank lower grade gas? If yes, how much should I mix?I will really appreciate your reply and advice.
Thanks...A. Okay, by the numbers...
1. If the owners manual says to use 91 octane, then that is what you should use. Although I have never heard of a Sentra that needed 91 octane.
2. If I could tell you the exact problem from here, I would never need to go to the shop. I could phone my diagnosis in. Based on feedback I get, I'm running correct about 70% of the time which is a long way from 100%.
3. Knocking can be harmful in that it can burn valves and pistons. This doesn't happen over night however. It occurs after driving for an extended time with this condition.
4. I would go ahead and put the booster in now following the directions on the can precisely.
Additional Information provided courtesy of ALLDATA
