Gas Mileage Question

[EClass]

So....

I was getting between 18-21mpg pretty consistently city / hwy driving for the past 6 months. I was @ 49K miles and decided to have a tune before a big trip so I had my 50K service done + a few other items serviced. They changed oil, plugs, filters, etc....

Noticed that for the couple weeks after my service I was only getting max 18 and my average was like 16.4mpg.

I bought wheels and 33" tires and now I am around 14-14.5 hwy!! I know tires can affect it a little but why the big drop after my service? I was getting close to 400 a tank and my last trip was 290 close to fumes!

Does it sound like I have an engine issue or a bad sensor? Dealer said when they did service that a thread broke in engine taking one of the plugs out and they had to re-thread it. Could that plug / cylinder not be firing right and I'm running a 5 cyl without knowing it? Plug leaking possibly and I'm losing compression? Thanks for your help.

Thanks.

 

[AngryRedBird]

Comparison

As a comparison , I was getting roughly 18 - 21 like you, But I was running the 255/75/17 BFGoodrich Mud Terrains.. But just before last years vacation I swapped tires with another wrangler owner.. I ended up getting his Goodyear SR-A's.. I wasn't pleased with the Goodyear tires.. But it has offered us a substantial increase in mileage and fuel saving. Plus with fuel prices low at the moments.. We would normally fill up once a week.. Now it's more like once every week and a half.

I can't say that anything was done wrong with the jeep.. other than you mentioned that the dealership told you they busted a plug.. Perhaps the plug gaping is incorrect.. After all this is a common issue that the jeep is known for.

Lifted, Larger tires etc.. will decease any fuel economy.. Also could depend on any added weight within the jeep.. Adding bull bars, swing out tail gate etc.. is just adding fuel to the fire.

We'll prob throw this out the window also, when we lift our 08 and add slightly larger & wider Duratraxs..