Sorry another MPG thread -
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post #1 of 2 Old 11-18-2013, 09:29 PM Thread Starter
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1993 YJ Wrangler 
Join Date: Sep 2005
Location: Northeast Texas
Posts: 56
Sorry another MPG thread

Sorry about another MPG question but I couldnít find anything while searching the web.
I had my 4.0 professionally rebuilt, I got about 1k miles on it now. Prior to the rebuild I was avg. 14.5 mpg. After the rebuild I have been getting 12.5 mpg, this last check I got 11 mpg. What gives? Nothing else has changed on the Jeep and my driving habits are the same. The engine seems stronger with a little more power to it. Thereís no missing or ruff idling or any indication of a problem. The temp. runs at 195*-205*. Plugs look fine along with the air filter. I would think the rebuild would improve the gas mileage or at least not hurt it. Is there anything Iím overlooking that might drop my mileage by 3 mpg that I can check out?
Thanks, Eddie

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post #2 of 2 Old 11-19-2013, 02:00 AM
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1995 ZJ 
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You will see this with most new cars/engines, there is a point where an engine is considered "broke-in" and fuel mileage may increase a little with time. There are a ton of variables that go into fuel mileage but winter temps or simply colder temps will cause more fuel consumption. The engine will run richer with colder outside temps, and its also spending more time warming up which increases fuel consumption too.

I would give it a couple oil changes at least to see some improvement, but like already mentioned, it could be other things not even related to the new engine.
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