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Octane rating for 7.4 L engine
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Author:  Desert Steve [ Wed Jun 17, 2009 4:30 pm ]
Post subject:  Octane rating for 7.4 L engine

I have a 1995 258 Vista and have been using regular (87) octane fuel. I read a post somewhere, perhaps a different forum, that suggested using premium. I cannot find in the owners manual where the octane rating is specified. What octane rating fuel should I use?

Thanks,

Author:  Aussie_Horizon_190 [ Wed Jun 17, 2009 5:37 pm ]
Post subject:  Re: Octane rating for 7.4 L engine

If your motor runs fine on 87, then leave it. However, if it 'diesels' or runs on after you turn the ignition off, then you need a higher octane fuel such as premium.

Author:  Brett248Vista [ Wed Jun 17, 2009 7:15 pm ]
Post subject:  Re: Octane rating for 7.4 L engine

WOW a 7.4 in a 258? That should be a blast! :)

Author:  bndfishing [ Wed Jun 17, 2009 7:58 pm ]
Post subject:  Re: Octane rating for 7.4 L engine

Dieseling won't be solved by a higher octane fuel, that is usually a carburetor problem. The sign of needing a higher octace fuel is if you are experiencing predetonation or "ping" you will usually hear this under load. This is caused by the fuel in the cylinder igniting before the piston reaches the point where the spark plug is supposed to ignite it. Predetonation can be very harmful to an engine, but if everything is running fine your aren't getting any "pinging" you should be fine with regular.

Author:  teker [ Wed Jun 17, 2009 8:51 pm ]
Post subject:  Re: Octane rating for 7.4 L engine

I had a 94 258 with a 7.4 but I don't remember the recommend octane rating. I now have a 99 258 with a fuel injected 7.4 and 89 octane is recommended. I have used 87 when 89 was not available with no noticeable effects.

Author:  powellcrazy [ Wed Jun 17, 2009 10:11 pm ]
Post subject:  Re: Octane rating for 7.4 L engine

We had a 7.4L in our '95 245 sundowner. All I ever ran in it was the 87. Ran and performed great.

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