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tidester, host
1. Accelerate slowly
2. Keep highway speed to about 62 mph
3. Use AC whenever needed
4. Use cruise whenever possible
5. Keep tires inflated to 36 psi cold
My lowest mileage figure ever was 24.5 mi/gal. Currently my CRD has 8400 miles.
What your oil level. There is a tendency for some consumption in th first several hundred miles. You may need to add about one quart after 600 - 700 miles.
2nd Choice: Ursa TDX Premium Synthetic 5W-40.
Mobil 1 is a good oil, but tremendously over-hyped and over-priced. (And I firmly believe that the main reason that it is recommended - by name - in our owner's manuals is that DDC Cento (nee, VM Motori) who builds our CRDs, is 51% owned by Roger Pennske who is in bed with ExxonMobil.)
As far as speed, pay less attention to that and more attention to rpm. On my rig the lowest rpm I can get is about 1625 rpm(approx) and still maintain highway speeds of about 56 mph. If I drop to 55mpg the transmission downshifts and puts me up at 2000 rpm. You will just have to use the cruise control and find the "sweet spots" in your transmission to get the lowest rpm within a certain speed range. For me to get the 1625 rpm I have to go up to 60mpg and set cruise control, then back off to the 56-57mph range. For me 1800 rpm produces about 62-63mph speed. Just a few hundred rpm on a diesel makes a HUGE difference. 70mph at 2000rpm+ will easily bring you down to 22mpg consumption or lower.
This time the diesel engine is no longer listed as a option...
Yesterday it was there and I printed it out... today it is not...
Maybe Jeep dropped the diesel engine... anyone know??
Not sure how accurate the computer is. The calculated mpg for the tank based on gallons pumped was 25.7. I have a Limited with build date of June. Tire pressure was 32 cold and the display indicated 35/36 psi. 4 oz of Powerservice in the tank and included in the mpg computation.
I'm not sure what type of real world mileage will be the max I will ever see with this CRD, however, I am excited to find out. I bet I could beat Consumer Reports 11 mpg while towing a Prius and using full time 4WD!
Glad I was able to locate an 05 with Trac-Lok.
Mileage and RPM has been discussed on this site before. It was pointed out to me that the maximum mileage should occur at the top of the Speed Vs Torque curve. I've got a curve here that says the peak of the curve is about 1800 RPMs to 2000 for the diesel Jeep. After that the slope changes and the curve goes down. I usually drive about those RPMs and get pretty good mileage.
Is 1625 RPM better or the top of the Speed Torque curve? I guess the top of the curve is where the engine is the most efficient.
I think one of the posts said this had to do with the laws of physics. Maybe George Bush had those laws repealed with the tax cut.
Is 1625 RPM better or the top of the Speed Torque curve? I guess the top of the curve is where the engine is the most efficient
Mileage really has NOTHING to do with the torque curve. It only is a function of speed and RPM. The higher the speed at the lower the RPM (or throttle opening), the better mileage you will get.
The maximum Torque curve RPM is determined a WIDE OPEN THROTTLE. Unless you are cruising down the road at WOT, that to graph has zero to do with your mileage. The "Laws of Physics" guy had zero idea what he was talking about.
A bunch of my work requires me to drive on state roads where the speed limit is only 50 to 55mph, so I'm looking forward to testing this out.
As a side note, I just got 24mpg on my very first tank of diesel, not too bad for city driving and heavy acceleration to get the engine broken in... I did keep at least 50% of that driving at 1800rpm or less, but the other 50% was well above the 1800rpm zone.
At lower loads, the best efficiency may be at a different speed. For example, with no load, the lowest sustainable idle is most efficient. In theory, with no load, efficiency is 0, as no work is being done. With a minimal load, the most efficient speed would probably be pretty low.
What all of this fails to account for is gearing. Gearing reduces or multiplies the effective load on the engine depending on how the vehicle is geared. At highway speeds, in 5th gear, our CRDs are operating through an overdrive transmission, through a 1:1 transfer case, to a 3.73:1 rear axle ratio, for a final drive ratio probably around 3.2:1 or so. In other words, it takes 3.2 revolutions of the engine (through the tranny, t-case and driveshaft) to turn the wheels one complete revolution. So the load on the engine is effectively reduced to 1/3 of actual load, but RPMs required to move at a given speed are increased by a factor of 3.
So maximum efficiency when an engine is not running on a engine stand must take into account the load on the engine as affected by all gearing of the vehicle. For 99% of passenger car operational hours, maximum efficiency is somewhere below the torque peak, as they are not operating at full load. (The correlation isn't quite that clean, but it generally works out that way). So most cars are geared to be slightly below their torque peak in top gear at around 60-65 mph. For semi-trucks and larger vehicles, they are geared to be at the torque peak when operating, as they operate at or near peak load much more frequently. For off-highway vehicles (tractors, bulldozers, etc.), they are geared and engineered to operate slightly faster than the peak torque RPM, to allow the engine to actually 'build extra torque' as extra load is applied and as RPM drops slightly. This is what we refer to as torque bulge.
Hope I'm not too far afield here, but it's an interesting discussion.
The BEST mileage is when you are being given the finger by speeders passing you by and you are habitually late to work; which is welcomed by your boss, because you're too stoned on coffee to be helpful once you get there.
OR
Best mileage is the point of inflection on the torque curve, before maxima, after minima; determined empirically from uploading 43.3 trillion data points to a Cray supercomputer running the Hogue Model, w/ number of "The Fingers" subroutine disabled, through an Excel macro.
OR
The best mileage is on siphoned diesel, or that stolen in a "gas-n-go".
Owhee!
Bridgestone has a tire called the REVO. Have never used but I have spoken to a bunch of people who have them on their SUV. They are exceedingly pleased with them.
I would avoid Michelin. They are overpriced and after about 1/3 of the tread is worn, they start getting very allergic to water.
I have heard some positive things about Cooper tires.
For good pricing, go to www.tirerack.com
Good luck!
B. in Seattle
I have heard a manual-locking hub kit is very available for the Liberty. Earlier models, at least. I would love to know your results after installation !
If we compare a fuel injected diesel and a fuel injected gasser, other than differences in compression ratios and the timing of fuel being injected (and spray patterns, duration of spray, etc.), the primary difference is only that the gasser has a throttle body regulating the amount of air going into the engine and the diesel doesn't. Assuming that the computer doesn't change the amount of fuel being introduced into the engine when the throttle is in a steady position (which isn't a fair assumption, as the computer will vary the amount of fuel being injected based on load, engine temp, transmission condition (shifting/not, gear presently engaged, torque converter locked, etc.)), with either a diesel or gasser, holding the throttle steady would introduce a certain amoutn of fuel into the engine and produce a certain amount of power that would remain constant. In the diesel, it would be a function of the amount of fuel introduced and the efficiency of the engine as an air pump. In the gasser, it would be a function of the amount of fuel introduced, the amount of air permitted to pass the throttle body, and the efficiency of the engine as an air pump. Of course, adding forced induction, etc., can change all of that.
In either case, though, the effect of throttle is the same: it produces a certain amount of power. Reduce throttle, reduce power, hold or reduce speed. Increase throttle, increase power, gain speed. That's oversimplified, as it doesn't take into account grade, rolling resistance, drag, etc. But the basic premise is the same for gassers or diesels.
I 've had good results from these grippy tires. A bit pricy<$135 US.>20 bucks difference compared to most tires ,but worth it in my book.
Lots of rubber,compared to others.
But if you do alot of mud bogging in the fields and backroads ,you may find the mudterrains to your liking for maximum traction .
I know you are not partial to Michelins LTX M/S but I also had very good results with these as well. <$110 US.>
Check out the reviews if you like,they are both top rated.
www.1010tires.com/suv tire reviews
www.consumersearch.com/suv tires
Good luck ...
Speak Soon
Lightnin3
The "best" tire I have found, so far are the Michelin XLT, or Crosstrainer. They are expensive, $ 150. Sams Club, BJ, CostCO all sell a variant of the tire at about $ 110. According to the Michelin website, the variants and the originals are essentially the same.
Cooper has a SUV tire for about $ 60, but I can't find much info on it. One dealer recommended Yokohama Geolander, but its the OEM tire on my son's Forester and I can't believe that it would be good on the jeep. I won't put Bridgestone Firestone on my car due to the fact that twice (once in the late 70s and about 5 years ago) they produced tires which were defective and lied about it. That is just my feeling, but alot of people do recommend the Revo. One alternative may be the BFG Longtrail which I had on my Xterra and got good service from.
All the dealers have recommended going up one size to 235 to get a "squarer" footprint, for whatever reason.
I have about 10,500 mi on my CRD and can spin the OEM tires from a dead stop. In addition, they squeal on curves when there is little force being applied. I will replace before the snow, but have not made a final decision as yet
LK
Good luck! LK
P.S. They didn't have "employee pricing" in july.