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I recently started a post to find out everyone's fuel milage and received some good info from members. This week I put it to good use on a 1,000 mile trip to Nashville and back. I took it in about a hundred mile increments and varied my speed, use of cruise, etc to see what worked best.
First of all let me give you some background on me and my fj. I have driven Porsches primarily for over 50 years, and am accustomed to pretty much staying in the left lane and driving the maximum speed I can get away with to cover long trips as expeditiously as possible. I have always been able to do this in Porsches and still get reasonable milage as well. We recently replaced our Macan twin turbo with the fj and I have found that if I drive it as I did the Macan my milage is in the single digits. This isn't all that big a deal on local driving, but our preferred offroading is of course in Colorado which is about 35,00 miles of interstate away, That makes optimizing milage more critical to me so as not to break the bank.
As for the fj, it is a 2010 with automatic trans and 21K miles on the clock with 3 in ch lift, 34 inch KO2"s and quite heavy Budbilt rock sliders as the only mods. It still has the original spark plugs in it ( not sure new plugs would make a significant difference at this milage ). Running perfectly.
That said, I found that use of the cruise at any speed below 70 was counter productive. On backroads with curves and ups and downs I found that between 50 and 60MPH and varying the speed going upgrade to keep it from downshifting produced my best results. I relied more on the rpm's than the speedometer. I got 15 MPG by keeping the rpm at 2K or less. When it downshifted and the rpms rose to 3400 t0 4,00 gas consumption suffered. I am happy with that. On the interstate (I 40 which has a good bit of up and down grades I first tried the cruise at 65mph and found that the transmission did enough shifting to defeat the purpose. Below that was even worse. I found my sweet spot at 70 to 72 using the cruise control which gave me consistently a solid 18 to 19 mpg repeatedly. It seems that that speed gives you enough momentum to climb most of the upgrades with enough momentum to minimize downshifting and still not push too much wind. I found that my best results came when I kept the rpm at or below 2 K which on the interstate is 70 to 72.
So as difficult as it is for me to stay mostly in the right lane at 70 mph and add significant time to our long trips it does cut my fuel costs by about 40 percent which saves several hundreds of dollars on a Colorado trip I can us the savings for more mods. Thanks to everyone who shared their info with me in the earlier post.
 

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I generally agree with your findings, and have found that the use of cruise control in hilly country will not achieve best fuel economy.

I find the transmission shift programming to be particularly irritating, as my non-lifted '14 AT (265x75R16 KO2s) will easily pull a given grade in 5th gear when NOT in cruise control, but when cruise control is on, that same grade, at the same speed, will invariably force a downshift to 4th and sometimes a screaming 4K RPM downshift to 3rd.

After several trips from California to Colorado, I've found that using cruise control only on dead flat sections and turning off the AC during long steep grades helps achieve the best fuel economy.

Probably the single most useful addition to minimize fuel consumption is to add a means of observing instantaneous fuel consumption, which will immediately show you the combinations of RPM, throttle opening, gear, and engine load that minimize fuel burn. For me, that is an inexpensive ($25) Bluetooth OBDII dongle plugged into the FJ's OBD port, and the app Torque Pro ($5) running on an Android phone or tablet. You can configure the display to show instantaneous fuel consumption, long-term fuel consumption, and trip fuel consumption. If you're a gear head, you can also display scores of other vital engine & transmission data: ignition timing advance, commanded and actual air:fuel ratio, engine coolant temp, transmission temp, mass airflow rate, relative throttle opening, % engine load, etc., etc.

Going from a series of slippery Porsches to an aerodynamic brick like the FJ must be quite a transition.
 

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If your gearing is stock and running 34” tires using 4th gear up to 60mph or so will give better mileage and if you use cruise it will work more smoothly also.

If you use a scan gauge and monitor throttle position, you will find the throttle farther open in 5th than in 4th at exactly same speed. In these instances 4th will give better mileage even though it is Rpm is higher.

Headwind velocity and direction play a big factor in FJ fuel mileage


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I get around 21 to 22 on my 2012 3 inch lift cruising around 65MPH.
 

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Great info. I’m planning to drive Seattle to CA, Bay Area in July. I’ll definitely make use of this

Thanks! ??
 

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If your gearing is stock and running 34” tires using 4th gear up to 60mph or so will give better mileage and if you use cruise it will work more smoothly also.

If you use a scan gauge and monitor throttle position, you will find the throttle farther open in 5th than in 4th at exactly same speed. In these instances 4th will give better mileage even though it is Rpm is higher.

Headwind velocity and direction play a big factor in FJ fuel mileage


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I believe the same, that in general, going uphill a lower gear (and higher RPM) is generally going to be more fuel efficient. 'Lugging' an engine isn't good for it, as I understand it. You might not be 'lugging' going up a certain hill in 5th, but a higher throttle position in a higher gear is generally not as efficient as a smaller throttle position in a lower gear (albeit, higher RPM.) I've seen the discussion before about the cruise control downshifting too easily. I wonder if the cruise control logic is tied to the transmission controller? In a simplified cruise control, it's just controlling the throttle, so if you drove it manually, exactly the same, there'd be no difference in shift points. If, however, the Cruise integrates with the trans controller, it might be triggering downshifts (and upshifts) at different points than are triggered when applying the throttle independent of the cruise - possibly to even better fuel mileage. I'd really like to see some solid testing to show one way or the other, whether the cruise control is more efficient or not. Unfortunately, testing with other vehicles isn't a good reflection of the engine/transmission/aerodynamics/weight etc. of the FJ. Also, in my opinion, one person's experience isn't enough, it needs to be a larger number of people, and all using a pretty standard set of testing.
 

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If your gearing is stock and running 34” tires using 4th gear up to 60mph or so will give better mileage and if you use cruise it will work more smoothly also.

If you use a scan gauge and monitor throttle position, you will find the throttle farther open in 5th than in 4th at exactly same speed. In these instances 4th will give better mileage even though it is Rpm is higher.

Headwind velocity and direction play a big factor in FJ fuel mileage


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This is generally not the case with typical non-boosted engines like the 1GR-FE in the FJC.

Watching fuel consumption vs mass air flow rate vs RPM using Torque Pro, I always see that for a given load condition, higher RPM/smaller throttle opening will burn more fuel than lower RPM/larger throttle opening. You need to monitor actual mass air flow in CFM, and not just relative throttle opening.

The biggest internal losses in a normally aspirated IC engine are frictional losses and pumping losses. The frictional losses increase rapidly with RPM, while pumping losses are reduced at higher throttle openings. There are scores of research papers available on the net that prove this conclusively.

Truthfully, I am not comfortable with the FJ's engine "stock" ECU/transmission ECU programming, which allow large throttle openings at relatively low RPM (1,200 or less) without downshifting. Even though this really isn't really "lugging" the engine, I manually shift into a lower gear to reduce cylinder pressure (reducing rod bearing and piston ring loads), and accept the slightly increased fuel consumption.
 

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OK....now do this with the Raptor ECU upgrade. Seems like you have the money to spend and I have read nothing but great reviews on trans shift points and responsiveness (which drives me nuts on the FJ anyhow esp after going to larger tires and lift).
 

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This is generally not the case with typical non-boosted engines like the 1GR-FE in the FJC.

Watching fuel consumption vs mass air flow rate vs RPM using Torque Pro, I always see that for a given load condition, higher RPM/smaller throttle opening will burn more fuel than lower RPM/larger throttle opening. You need to monitor actual mass air flow in CFM, and not just relative throttle opening.

The biggest internal losses in a normally aspirated IC engine are frictional losses and pumping losses. The frictional losses increase rapidly with RPM, while pumping losses are reduced at higher throttle openings. There are scores of research papers available on the net that prove this conclusively.

Truthfully, I am not comfortable with the FJ's engine "stock" ECU/transmission ECU programming, which allow large throttle openings at relatively low RPM (1,200 or less) without downshifting. Even though this really isn't really "lugging" the engine, I manually shift into a lower gear to reduce cylinder pressure (reducing rod bearing and piston ring loads), and accept the slightly increased fuel consumption.
I will put it this way.
If against a 30mph headwind at 60mph in 5th , the hand calculated mileage will be higher in 4th than 5th AND coolant temp will be lower.
As throttle opens under high load and lower rpm timing backs way off.

I can beat cruise control mileage any day on any road (with my foot manually controlling).


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I have a scan gauge installed in my FJ and always monitor my MPG, the sweet point is about 60 MPH, but in order to avoid blocking others on interstate, I normally use 65 to 70.
I can get 22 to 24 MPG if at 60 MPH, but any red light or brake will significantly drop the MPG, sometimes to only 12 MPG.
 

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So as difficult as it is for me to stay mostly in the right lane at 70 mph and add significant time to our long trips it does cut my fuel costs by about 40 percent which saves several hundreds of dollars on a Colorado trip I can us the savings for more mods.
Those are the tradeoffs... personally, until I am retired I am willing to trade a few $$ for gas to save a day of vacation time on the road on a long trip.

When I go to Moab or Ouray, I generally will drive Minneapolis to Denver in one day, over 900 miles. Going 70 instead of 75 will cost me an hour and a half additional, which can put me over the tipping point as far as making it in one day. I look forward to the day when I can drive at a leisurely pace and not care.

BTW in my 2010 I have never gotten less than 14 mpg, even towing a small camper in 4th gear at 75 mph (well, maybe I did on the trail sometime but I don't keep track of mpg then).
 
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