Gas Mileage Update: Atlas I-5 in an FJ80 (1 Viewer)

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We now have several thousand miles on the FJ80 with the I-5 H3 motor in it. Highway mileage is averaging in the mid-19s, which is at least 30% better than the 3F-E.

The big change is in "in town" commuting mileage, though, with trips to the office, to shopping, in city traffic and suburban driving. With the stock truck, the "low fuel light" could pretty much be counted on to come on between 200 and 205 miles, taking about 20 gallons of gas. With the Atlas motor, under the same conditions, I can pretty much depend on 315-325 miles of range before the light comes on-- For in-town usage the mileage is considerably better.

I'm still pretty sold on the conversion, with the caveat that I'd have used the I-6 if the truck was going to be used more for towing.
 
Yes, power and torque are both up a lot. (There's another thread from a few months ago that goes through a lot of the details.) Spec'd power was 242 HP and I think we are getting all that and a bit more with a K&N set-up and cold air intake.

The big difference is the weight savings-- the truck's lost several hundred pounds in the swap and feels much quicker. The Atlas and the 4L60/70 transmission are both all-Aluminum, much lighter than the iron-block 3F-E.
 
When it was stock I got mid 19s from the 1FZ-FE

With the lift, ARB, tires, 3" exhaust, new o2 and in town driving 225 or so is usually on the trip odo when the light comes on. But that is really 250 miles due to the speedo not being corrected.
 
When it was stock I got mid 19s from the 1FZ-FE

With the lift, ARB, tires, 3" exhaust, new o2 and in town driving 225 or so is usually on the trip odo when the light comes on. But that is really 250 miles due to the speedo not being corrected.
That's really good-- all my Cruisers have been FJ80 and earlier (FJ40 and FJ60, too), but I was usually getting only 10-11 MPG in town and 15 or so on the highway with the 3F-E.
 
my 97 is stock and I have never gotten over 16.76 mpg.(highway)..about 12 or 13 in the city...I think that is pretty normal.

Keep us updated about your I5 conversion.....I think you are going in the right direction....

goodluck.....
 
Why would you put a crappy GM motor in a Toyota?????? :meh:
 
Why would you put a crappy GM motor in a Toyota?????? :meh:

Lemming! :flipoff2:

J/K, 4th gen GM powerplants are artwork. I would give one a serious look if I was ever in the market for a swap.
 
Lemming! :flipoff2:

J/K, 4th gen GM powerplants are artwork. I would give one a serious look if I was ever in the market for a swap.

X2. Opening the hood of a new 2500 series Sierra/Silverado/Suburban/Yukon is like finding a diamond in the rough. The diamond being the 6.0L, the rough being the garbage surrounding it :flipoff2:
 
Why would you put a crappy GM motor in a Toyota?????? :meh:
Well, the quick summary is:

58% more peak power
10% more torque, across the board
40% higher redline, with VVT, means "more area under the curve"
35% better fuel economy

And, the clincher, 400 pounds of weight savings.

It's not everybody's deal, but for a multi-use truck (commuter, winter rig, some off-road, light towing) it's working pretty well. It could always blow up tomorrow, whereas my 3F-E might run another 300,000 miles, but I like it so far.

YMMV
 
X2. Opening the hood of a new 2500 series Sierra/Silverado/Suburban/Yukon is like finding a diamond in the rough. The diamond being the 6.0L, the rough being the garbage surrounding it :flipoff2:
Yeah, the Bob Lutz observation turns out to be the case, IMHO: All those billions of R&D $$ GM spent exclusively went into drivetrain development; the 27 cents that were left over went into "interior components" and "fit-and-finish"...


Those 6.0L and 6.2L motors are amazing now, with the LS7-derived heads and ports and VVT. There's a shop down in Texas getting 550HP out of the 6.2L with a cam swap and tune.
 
Ooohhhhh, the 6.2 in an 80 would be NUTS. It puts out 400 HP in stock form :eek:


:idea:


Fawk the 454, I'm going with a 6.2 when I swap. :D
 
That is some pretty sweet results!

My Denali has the 6.0L and its a beast hp and torque wise, just doesn't get great mpg's... however, I had a Silverado with 5.3L and it consistently got 20-21mpg on the highway, and it was a Z71 4x4. My Z06 can get 30 on the highway and 20 around town. GM knows how to build a quality power plant... they just can't seem to get the rest right lol.

As soon as I can find the right FJ80, I'll start setting aside my pennies for a swap.
 
GM V8 Motors in an 80?

Ooohhhhh, the 6.2 in an 80 would be NUTS. It puts out 400 HP in stock form :eek:


:idea:


Fawk the 454, I'm going with a 6.2 when I swap. :D


Yeah, ironically all the work on the 3rd and 4th Gen LS motors has pretty much made the "Big Block" obsolete. (Although if anybody has a 502 RamJet crate motor they want to get rid of-- I'll happily take it off their hands... ;) )

The neat thing about the 4-gen motors is all the commonality. The L92 (6.2L) in the Denali and Escalades shares a lot of tooling with the LS3 Corvette motor (spec'd at 430+ but capable of a lot more with a tune.), so you can do builds to pick up a lot of power with off-the-shelf (or, just out of the scrap yard) truck parts. The heads, in particular, are notable for flowing really well and are from the high-volume production GM truck product lines. People are plunking L92 heads and L76 intakes on stock Chebby's and Pontiacs (RIP) and picking up big gains in HP.
 
That is some pretty sweet results!

My Denali has the 6.0L and its a beast hp and torque wise, just doesn't get great mpg's... however, I had a Silverado with 5.3L and it consistently got 20-21mpg on the highway, and it was a Z71 4x4. My Z06 can get 30 on the highway and 20 around town. GM knows how to build a quality power plant... they just can't seem to get the rest right lol.

As soon as I can find the right FJ80, I'll start setting aside my pennies for a swap.


For a V8 swap into an 80 the 5.3L seems to be the sweet spot. I think that's a common conversion done by the TLC4X4.com guy down in LA... Gets you to 285/325 HP/TQ while picking up a lot better gas mileage. I don't know if they change final drive gearing or not-- going down to 3.73 from the 4.10 gears would help the mileage a bit more, given the LS motors have such a broad torque curve.

Of course, the 6.0 and 6.2 motors would be monsters in there, too.

I have a friend up here with a new C6 Corvette with the LS3. He claims to get over 30 MPG on the highway. In car that will get to 60 in 4 seconds and top out on the scary side of 180. :steer: Amazing.
 
I like the larger LS* motors that have the variable valve timing. I have priced the 80 series t-case to GM trans adapter as well as the total of the swap. My 1FZ-FE aint broke even near 200k so I wont fix it just yet. I think I will just build it up and turbo it when it finally acts tired.
 
I believe the 5.3L's got a power boost after 2005... to 295/335. Nothing major, but every lil bit counts lol.

Imagine a 8.1L/Allison swap:eek:

What have you towed around, now that you've done the swap? Anything about the size of a smaller wake boat?:D
 
I believe the 5.3L's got a power boost after 2005... to 295/335. Nothing major, but every lil bit counts lol.

Imagine a 8.1L/Allison swap:eek:

What have you towed around, now that you've done the swap? Anything about the size of a smaller wake boat?:D

Mainly just my Spyder (about 1400 #) on the light-duty car trailer. You hardly know it's back there. If I were towing big boats, equipment trailers, big campers, etc I'd be the first to say that the Atlas wasn't the right choice. Of course, with that kind of load, I'd never want to tow with the 3F-E, either! :bang: Life's too short to take hills at 34MPH.

For the larger enclosed trailer (fits two cars, plus tools and gear) I have a 6.0L towing rig.
 
Your forgetting one thing. GM engines are unreliable. The 3F-E will out last that engine easily. Kiss your 3F-E it loves you. Doubt the Atlas I-5 does. :meh:
 

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