Hey all, I bought my 96 XJ 4.0 HO back in june. I have been using 87 octane since I bought it and have not had any pinging under load or otherwise. A couple weeks ago I put some cheap ( not just inexpensive) gas in and it was pinging like crazy. I added some octane boost and injector cleaner. Now even with quality 87 octane I get some pinging under load. Could the bad gas have messed up the timing. Isn't it controlled by the computer with a nock sensor etc. I am going to do a tune up sometime. I don't know if that would help. I know the principal is that the gas is detonating too soon and trying to expand while the piston is comming up still. This can be due to a dirty engine I suppose. Do others have problems running 87octane? Thanks for all the help. cheers