Case:

Trying to Improve my MPG in my 91 XJ.

I've been doing some research and I've heard the claims of Throttle Body Spacers, new injectors, and regearing, But I'd rather hear from the people in this case before I drop the money on something.

Now, I'm by no means a noob to vehicles, so installation of things shouldn't be out of reach. I'm just curious as to ways people solve MPG issues. I'm not trying to make prius numbers, but I would be happy at 17 or 18. Are performance mufflers any help to MPG?

Here are some specs on my XJ now,

4.0 HO
AW4 Auto Tranny
3.5ish lift on 32 BFG ATs

I've got the HP Dana 30 up front and the Chryco 8.25 in the back.
Towing Package, so the gears = 3.73.

Any help or advice at all is appreciated! Thank you all very much!

 

1.get a cold air intake bout5-10hp 10%fuel mileage
2.cat back exhaust 5-15hp and 10%fuel increase
3.get a good header bout 5-10hp

 

yes exhaust helps
high flow cat, better flowing airfilter,cooler air in the air intake

those are common

now not as common
ditching mechanical fan and switching to electric
neon injectors
bored throttle body
00 or 2001 intake maifold

im on 33s with 3.55 gears, have all this except for last 3 (i have it just to lazy to do) and im getting 15-17 in town 19-20 on highway.

also after you do any of these disconnect your battery and let your computer reset

 

exhast and intake woulf help and maybe net you a totall 1-1.5 mpg if you do both! and new plugs and injectors will get you another mpg as well...but most of all is gears. but you already have a high gear ratio...so i dont know. you best bet would be to go back down to some smaller 31 inch tires or even 30s

 

your gears are pretty good but if you have auto with o/d id swap some 4.10 in

 

injectors from a dodge stratus also work there was someone on this forum that said he got a 5mpg increase from stratus injectors....im going to the jy this weekend to get myself some

 

Hey everyone!

Thanks for all the tips and Lightening fast response.
Definitely going to look into everything you guys reccomended.
And unlike most of the newbs, I will keep you all updated and show the following through.

Haha, and now my dirty little secret. When I was 17, I wanted so bad to sound like I had dropped $$ on exhaust. So I did what any normal 17 year old wannabe does, and cut my muffler. I kept my Cat though. I am very pleased with the sound, everyone asks if its a flowmaster haha. Could this be a cause of my low MPG? Do i need to man up like the rest of the world and do it the right way?

(I'm almost 20 now, so I'd like to think that my wannabe days are done)

 

00 or 2001 intake maifold

everyone i know who has done this swap has lost h/p i wouldn't recommend it

 

i have heard that releases to much back pressure ans as a result you lose h/p i say get a new system and tell us what you think

 

Do the basic tune up too.

 

Alright, thanks for the advice everyone! means a lot!

 

Install a vacuum gauge and keep the needle at 15 or higher. Best $20 u'll every spend for better mpg.

http://cgi.ebay.com/ebaymotors/JDM-2...item5d2a2bf0c4

 

http://www.fueleconomy.gov/

Your year is listed as 14 to 18mpg. Good luck.

 

Does tall gearing with large tires do MPG damage? dont mean to thread jack i have 32's and 3.55 gearing and can see the claim for that.

 

hey thanks a lot man, definitely will do this coming payday!