8.9 mpg?

sandman · **Joined:** Fri Sep 08, 2006 10:40 am **Posts:** 40

So I just recently got my KJ back from having an engine swap completed. Mechanic thought it was going through gas a little fast so I filled he up with 89 octane and drove a half tank. Refilled the tank and WHAT...8.9 mpg? Called my mechanic and he said the engine passed both the compression test and leaks own test. He put a new pcv valve, belt, plugs, and air filter. He suggested a bottle of injector cleaner, which I added.

What else should I be looking for? I know I should be getting at least 14 mpg.

Thanks in advance

JeepinJarhead03 · **Posted:** Mon Feb 13, 2012 11:32 pm

Until it's been ran cold to hot and cooled off and ran again a few times it'll get poor mpgs, once the engine has gone through the efficiency learning process it should pick back up to 15ish - first 100ish miles depending on the type of driving you're doing - the engine is basically learning - it'll be worth taking a deeper look at if it's still getting that kind of mileage on the 3rd half tank or so

sandman · **Joined:** Fri Sep 08, 2006 10:40 am **Posts:** 40

Does the computer need to relearn after the battery is disconnected? I replaced the battery a week after i got it back and have also disconnected it to add some lights.

I'm guessing a fuel filter wouldn't hurt?

JeepinJarhead03 · **Posted:** Tue Feb 14, 2012 1:26 am

yep it goes through a relearn when the batts disco'ed - pretty much 50-100~ miles, with 3 cold to hot and complete cool off periods give or take - that's pretty much what it'll take to get the OBDII system re-ready for emissions such as the O2's and what not which also affect efficiency but there are other recalculations and what not going on during that period as well and for a time afterwards, some systems take a bit longer, some much shorter

I wouldn't be concerned until that process was well out of the way

Fuel filter won't hurt, but it may be somewhat irrelevant in the grand scheme of things at the time, considering the battery disco's and what not

8.9 mpg?

Who is online