My 2000 TJ with its 2.5 L Inline 4 cylinder gets in the neighborhood of 17 MPG. I've been considering updating the engine and tranny/transfer case to achieve 30 plus MPG. Or is there some updates to the current configuration to improve the MPG?
Improving fuel economy
- Thread starter Mika
- Start date
ErikOffroad
TJ Enthusiast
I think the best mpg received out of a tj was by swapping a small Volkswagen diesel into it. And that I don’t even think is 30 mpg
ErikOffroad
TJ Enthusiast
U want better gas mileage don’t daily drive your Jeep and go buy a Ford Fiesta
ErikOffroad
TJ Enthusiast
With fuel at the price it is u would have to drive a very long distance before ur fuel savings would ever recoup the cost of a engine swap. On top of that it’s not the engine that is really the problem. It’s aerodynamics
ErikOffroad
TJ Enthusiast
Lucky for us fab 4 makes a “great product “ to improve aerodynamic efficiency 
https://www.extremeterrain.com/fab-fours-jk-grumper-0717-jk.html
https://www.extremeterrain.com/fab-fours-jk-grumper-0717-jk.html
Good luck. You’ll never get 30 MPG from your TJ unless you swap in a diesel. Even then, it will be more like 28 max.
mgroeger
TJ Enthusiast
Sean Allen
Member
Sean Allen
Member
TJBob
TJ Enthusiast
In all seriousness, if you have a lot of money to spend (and skills), you can swap in a diesel like @Mike Alfano or @disjaukifa have done. Here are their build threads:
VM 2.8 turbo diesel frame-up TJ build
Project Felicity: 06 TJ Wrangler RHD V2403 Kubota Diesel Swap
@DieselJeep has done it as well with the Cummins R2.8 I believe.
This is the ONLY way you'll ever see 30 MPG from your TJ. It also won't be cheap.
VM 2.8 turbo diesel frame-up TJ build
Project Felicity: 06 TJ Wrangler RHD V2403 Kubota Diesel Swap
@DieselJeep has done it as well with the Cummins R2.8 I believe.
This is the ONLY way you'll ever see 30 MPG from your TJ. It also won't be cheap.
You will spend much more chasing mileage than going out and buying a used Hyundai Accent and using it for your daily. You can practice hypermiling- which will get you up to 20mpg, but if you drive a JEEP, I imagine you won't like it. There is no "magic bullet".
We can get our 200 TDI Defenders to approach 30mpg on the highway- but they already have Direct Injection Turbo Diesels, tons of torque and a crazy high overdrive gear. Of course, we also have to drive 55 in a 70mph zone to do it.
We can get our 200 TDI Defenders to approach 30mpg on the highway- but they already have Direct Injection Turbo Diesels, tons of torque and a crazy high overdrive gear. Of course, we also have to drive 55 in a 70mph zone to do it.
I looked at the cost of a Cummins R2.8 swap at one point. To have it done right (working AC, factory gauges, etc.), it costs upwards of 20k (more like 25k if you factor in the labor).
Yes, you can get up to 30 MPG out of it, but at what cost? If you genuinely paid that much money to swap that engine in with the hopes of getting better fuel economy, the amount of money you just spent on the swap far outweighs what you would spend on extra gas over the next several decades I would assume (unless you drive 100k a year or something).
The solution to your question is simple: Buy a secondary vehicle that gets better fuel economy.
Yes, you can get up to 30 MPG out of it, but at what cost? If you genuinely paid that much money to swap that engine in with the hopes of getting better fuel economy, the amount of money you just spent on the swap far outweighs what you would spend on extra gas over the next several decades I would assume (unless you drive 100k a year or something).
The solution to your question is simple: Buy a secondary vehicle that gets better fuel economy.
Yeah I'm going to argue with this fact
. Going with you Hyundai Accent example lets just say you are getting one in decent shape for between 3K ~ 5K. Once you have the second vehicle you have to pay taxes, insurance, wear parts, gas etc. My swap not including all the extra and ridiculous stuff that I'm doing, could easily be done for around 3K ~ 4K max, and honestly I'm not at 4K yet in parts. That is the V2403 engine, the adapters, the motor mount adapter plates, the AW4 transmission, everything. Yeah I've been working on it for 6 months now, but I'm looking to be anywhere between 30 ~ 35 mpg once I'm done.
Considering the best MPG I ever saw was 19mpg with my 4.0l on one tank which I was able to do because I took out the front driveshaft, my average was usually between 14 ~ 16 mpg. So yeah factoring in all my cost and time but also the amount of miles I drive a year, I should recoup the cost of the swap in a little over a year.
Also I don't have the added expensive of the Hyundai Accent. Again this is just a personal preference and I'm doing all the work myself. It's not easy and it's been difficult with it's own hiccups but once it's on the road this will be my daily driver!
-Grant
How do you calculate you'll save nearly $4,000 in fuel savings in a little over a year. To say I find that hard/impossible to believe in realistic driving distances would be an understatement.
That's like my relative who owns a store and said workers stole 20,000 dollars of a certain product one year. My calculations told me he only purchased and sold about 18,000 dollars worth of it that year . His theory made no sense.
If you want better mileage out of that one , just don't drive it.
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Okay admittedly I did the math in my head wrong
. I drive about 20,000 almost all not for work as I work from home. I put 100K on my Jeep Liberty is just over 50 months truthfully. So 20,000 miles / 15 miles per gallon is about 1333 gallons of gas at an average in my area of 2.50 would be $3,233 spent on gasoline.
Take the same mileage for 20,000 miles but for 30 miles per gallon and that is 666 gallons of diesel at $2.80 for around $1864 in diesel fuel. That is a savings of $1369, so that would be about 3 years to recoup the cost of the swap if I only get 30mpg.
Take the same mileage for 20,000 miles but for 35 miles per gallon (my goal) and that is 571 gallons of diesel at $2.80 for around $1599 in diesel fuel. That is a savings of $1634, so that would be a little over 2 years to recoup the cost of the swap if I get 35mpg.
So yeah my math was wrong but if the above should be correct. Also I drive a ton for the enjoyment of it so I would see the benefit sooner.
Thanks
Grant
mgroeger
TJ Enthusiast
I was able to save 10mpg with this modification...
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