Given that it’s now 2018, I wanted to ask a question that’s been asked a handful of times before, albeit back in the early 2000s. I just picked up a used 2004 Jeep Grand Cherokee with 83,000 miles on it. I decided to bite on it because, with the exception of undercarriage rust, the single owner took incredibly good care of it. It was hard to find a 2nd or 3rd gen Grand Cherokee in my area with only 83K miles, and even harder to find one that looked brand new.

The thing that doesn’t excite me is fuel efficiency. Of course, I wouldn’t have bought it if I wasn’t ok with averaging 16 mpg. However, I figured it’d be worth asking some Jeep owners the following:

Other than changing my driving habits and conducting regular maintenance/tune-ups, how can I improve the fuel efficiency of this vehicle? It’s been 14 years since the vehicle was released, so are there some new aftermarket parts that are good for improving fuel economy?

These are the recommendations I’ve found so far by looking at old threads:

1. K&N Intake
2. Fuel Injectors
3. Superchips Programmer
4. Exhaust

Looking forward to some tips/tricks. Thanks

Thanks Dave. I won’t say that’s not disappointing to hear. I hoped some combination of tweaks could bump it 2-3 mgs but i guess 16 will have to do!

Avoid K and N . High flow catalytic converters and high flow mufflers will definitely help . Tire size , the fuel and ignition system being in top condition , a good clean air filter certainly helps. I think for the most part good maintenance is key but like Dave said exhaust is the biggest impact .

When you say the converters and mufflers would help, how much improvement might that be?

I don’t want to say a figure because I don’t want to mislead you and I don’t have a definitive answer . However a lot of factory exhaust systems are quite restrictive and a good quality exhaust system could PROBABLY Net you a couple miles per gallon if I had to make a bet .

When I was in college obtaining my automotive technology degree the professor that taught our particular brand of classes really pushed the same concept as did every text book we had . However just about every dyno test on any new camaro/Mustang/challenger shows significant horsepower gains from repalcement or even elimination of the factory catalytic converters and mufflers look up numbers on Coyote 5.0 Mustangs for example . I preached it during college but everything I’ve seen or heard of in the real world screams otherwise . On the flip side a 14 year old converter can become quite restrictive compared to new off the showroom floor.

one of the most common automotive myths . Engines do not need backpressure to run correctly. Look it up . However high flow cats can potentially play hell with oxygen sensors because they’re going to receive more of a “response” than they’ve been used to . So a problem oxygen sensor will shine with a high flowing exhaust system .