My goal is to get 25+ mpg from my 99 XJ with 30 x 9.5 R15 ATs - Page 30 - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Cherokee & Comanche Forums > XJ Cherokee Technical Forum > My goal is to get 25+ mpg from my 99 XJ with 30 x 9.5 R15 ATs

Spartan Locker Promo Running now @ ROCKRIDGE 4WD plus FREESpartan Locker Special Forum Prices Dana 30 44 60 Ford 8.8Steinjager TJ tube doors

Reply
Unread 08-14-2013, 11:49 PM   #436
Charley3
Web Wheeler
1999 XJ Cherokee 
 
Join Date: Mar 2013
Location: Western, WA
Posts: 2,821
My 205F Gates 33010 thermostat is working really good for me in my moderate climate. I'm happy with it.

If I want to try a slightly warmer stat (which I might try someday) I'd try a 205F ACDelco 12TP1F, which I think might be slightly warmer (like maybe 2F to 5F warmer) than Gates based on a user's report, though I'm not sure if ACDelco is really warmer. At this point I can only say the ACDelco is rumored to be slightly warmer than Gates.

I plan to test the 205F ACDelco stat myself, when I get around to it.

The 205F Gates has been ideal in my moderate climate. I'm sure it'd also be good in a cold climate.

The 205F ACDelco might be even better in a cold climate.

The goal is to run 210F in your climate, or as close as possible to 210F.

In colder climates (or even Winter in my moderate climate), it's difficult to run warmer than 200F in Winter on highway, even with a 205F stat. That is part of the reason(s) why all electric fans (off in Winter) and partial grill covers are helpful to achieve 210F (or at least 200F+), as well as electric fans save energy (by not coming on in Winter) and grill covers improve aerodynamics. Most important in Winter is they help engine run warmer.

IME gas mileage is best at 208F to about 213F. Any hotter and stock electric fan comes on at 215F, which uses energy, which reduces gas mileage.

IME gas mileage is reasonably good at 200F.

IME gas mileage is mediocre at 195F.

IME gas mileage is poor at 190F, and terrible below 190F. The farther below 190F, the worse it gets.

So using the above info, people in moderate and cold climates can see the importance of op temp and set some goals and choose mods to get to full op temp (210F) year round, or at least get close enough (200F+).

===

I've been experimenting with this for 20 years on 3 Jeeps and 2 cars in a moderate climate that is sometimes cold. I have developed a good feel for how op temp affects gas mileage, especially in 4L Jeeps.

However, the engines I've done this on were 1970s through 1990s cars/Jeeps, and a 2006 LJ (but that 4L engine was mostly an older design). I haven't tried changing stat temps or any other mods on recently designed car engines. I'd be concerned my changes might conflict with computer. However, many newer designes of cars already have warmer stats, electric fans, smoother under-bodies, positive rake, active grill louvers, and many other gas mileage tricks (that we've discussed in this thread) built into them at factory. So most newer cars don't need mods for gas mileage because they're already built-in at the factory.

What we are really doing with our gas mileage mods to our 4L Jeeps, and other older vehicles, is updating them to use modern technology in areas that benefit gas mileage. I like this because we get the best of classic 4x4 designs combined with some modern efficiency updates.

__________________
Sometimes I edit a post a few times to get it how I want it.
Charley3 is offline   Reply With Quote
Unread 08-15-2013, 12:33 AM   #437
RacerX
Registered User
1989 XJ Cherokee 
 
Join Date: May 2010
Location: Snohomish, Washington
Posts: 959
Quote:
Originally Posted by Newtons3 View Post
I still think your winter gas-guzzling blues have as much to do with the IAT as the coolant temp. I think you could benefit from relocating to a warmer location or actually arranging to draw warmer air.
I always thought Winter gas was better (more powerful, better chemicals, NO Alcohol, ...well no alcohol until last January!)
I had been trying to get a couple of 55-Gal drums to keep winter gas in for vacation season when gas$$ peak. (so much for that)

Anyway ... WTF is up with summer / Winter Gas anyway???

BTW, I'm also in west WA
__________________
4-wheeling is about going where others can't won't or don't think it's safe.
Freedom. Exploring the wilderness, or nature, whatever... - NOT paying to go on someone's roller-coaster ride, or go-cart track!
"The price of freedom is eternal vigilance." - Thomas Jefferson
RacerX is offline   Reply With Quote
Unread 08-15-2013, 12:52 AM   #438
Charley3
Web Wheeler
1999 XJ Cherokee 
 
Join Date: Mar 2013
Location: Western, WA
Posts: 2,821
Quote:
Originally Posted by 1997xj View Post
Along the same lines as charley3's post, any chance you guys can summarize the top mpg mods? My tires are aired correctly, roof rack off, fresh fluids, clean air filter, and alignment looks good. What's my next best move?
Most of the following applies to all climates. The 205F thermostat, grill cover, and mechanical to electric fan conversion mods are for moderate to cold climates.

A tune up obviously, tires not to knobby tread, narrower tires, good tire pressure, aluminum wheels, perfectly balanced tires, perfect alignment, high flow air intake from a warm area under hood (I prefer stock location, but opinions vary on that), 205F thermostat (brand does matter a lot), a partial or adjustable grill cover, and upgraded fuel injectors. Also synthetic oil in engine, transmission, transfer case, and differentials. I prefer Mobil One.

All those ^ things are all cheap, easy, and very effective, and should be your starting point.

Next, if you want to spend some money, or more effort, or probably both, you can take it to the next level by replacing your stock mechanical fan with a Taurus electric fan set to come on at 220F. Your stock electric fan comes on at 215F (if sensor working properly). You don't want both fans coming on at same tine (to much amp draw at startup).

However, there is nothing easy about replacing mechanical fan and wiring in an electric fan. It's great when done and working properly, but IME it's expensive to hire it done, and they might not wire it properly. I had that miserable experience with a 4x4 shop in the past. I had to pay a 2nd 4x4 shop to much money to rewire it properly.

Once the aftermarket electric fan worked properly in my Wrangler, it was awesome, but I spent more money getting it done than I'd ever get back in gas savings. Hopefully I'll have better luck this time on this XJ with my cousin doing the work.

So be warned, replacing mechanical fan with electric is not an easy undertaking IME, but when done properly it is a great improvement in a moderate or cold climate.

For more details, reread the OP carefully, then skim the thread, stopping to read the most important posts carefully.

===

Edited in Later: A free'er flowing exhaust would also help gas mileage a little, and power a little more, but you're not ready for that. The things I already listed would be the prerequisits, IMO.

Beyond all the above there is a lengthy list of additional things that would help too, but the essentials are the easy, cheap, effective prerequisits that need to be done. The more difficult or expensive things can wait until later, if you ever do them.

The cheap, easy essentials are things everyone should do. The more expensive, or more difficult, things are for economodder hobbyists, IMO.

I so far have done most essentials on my 99 XJ, but not all. The cheap, easy essesntials will get me to 24 or 25 mpg with 30" ATs, 1.5" lift, skidplates, and winch. I'm close to that now and I still have fuel injectors to install to complete my cheap, easy essentials, and an aerodynamic winch cover to make.

After that, I will (when have the money) want to spend some money and effort taking it further with exhaust, mech to electric fan conversion, and some more aerodynamic mods. Maybe a few other things too.
__________________
Sometimes I edit a post a few times to get it how I want it.
Charley3 is offline   Reply With Quote
Unread 08-15-2013, 04:42 AM   #439
Newtons3
Registered User
2006 TJ Wrangler 
 
Join Date: Feb 2013
Location: Baton Rouge, Louisiana
Posts: 723
Quote:
Originally Posted by rebelbowtie View Post
Mine stays around 204-208 but will creep up to 220 on the highway if I am driving on an extended grade and sometimes shortly after I start driving and then goes back to just under 210
Same here (on the Wrangler), but Ive done a lot to the motor and cooling system.
Newtons3 is offline   Reply With Quote
Unread 08-15-2013, 05:41 AM   #440
Newtons3
Registered User
2006 TJ Wrangler 
 
Join Date: Feb 2013
Location: Baton Rouge, Louisiana
Posts: 723
Quote:
Originally Posted by RacerX View Post
I always thought Winter gas was better (more powerful, better chemicals, NO Alcohol, ...well no alcohol until last January!)
I had been trying to get a couple of 55-Gal drums to keep winter gas in for vacation season when gas$$ peak. (so much for that)

Anyway ... WTF is up with summer / Winter Gas anyway???

BTW, I'm also in west WA
Gasoline is a blend of chemicals. That blend changes with application. Along with octane rating, fuel is specd by reid vapor pressure and boiloff temperature (typically at 10, 50, and 90 percent). Typically, the smaller molecules (shorter hydrocarbon chains) are lighter, will boil off quicker, and give the blend a lower vapor pressure. The boiloff spec indicates at what temp a given percentage of the blend will evaporate. The lower each temp is, generally, the lighter the blend is. Typically these lighter fractions contribute to faster, more complete burn and even more power, so as they evaporate, the fuel changes, usually for the worse. This means that road gas, stored usually outdoors in tanks for unspecified lengths of time, must be blended to match the ambient temp in order to have any shelf life at all. in the winter, when the temps are low, this allows the fuel companies to sell a lighter blend which would be unstable in the higher temps of summer. Now.... this was the best I could do on my tiny, retarded phone to briefly explain just one complex aspect of a much larger topic in a very small space, and I probably did a poor job. I would suggest reading something like the information on the VP Fuel website. They do a MUCH better job of explaining fuel than me.
Newtons3 is offline   Reply With Quote
Unread 08-15-2013, 05:54 AM   #441
ECL
Registered User
1998 XJ Cherokee 
 
Join Date: Dec 2005
Location: Easton, Pennsylvania
Posts: 223
Adding to Newtons3 comment, winter gas, being "lighter", is easier to start the car with. This was especially true back in the days of carburetors. Summer gas, being "heavier", evaporates less in the tank on a hot day. Less load on the Evaporative Control System (that charcoal canister thing...) or on pre ~1970 cars, less fumes going right to atmsophere. I worked at a refinery during college (~30 yrs ago). They changed their base blend 4 times a year.
ECL is offline   Reply With Quote
Unread 08-15-2013, 08:14 AM   #442
Newtons3
Registered User
2006 TJ Wrangler 
 
Join Date: Feb 2013
Location: Baton Rouge, Louisiana
Posts: 723
Quote:
Originally Posted by ECL View Post
Adding to Newtons3 comment, winter gas, being "lighter", is easier to start the car with. This was especially true back in the days of carburetors. Summer gas, being "heavier", evaporates less in the tank on a hot day. Less load on the Evaporative Control System (that charcoal canister thing...) or on pre ~1970 cars, less fumes going right to atmsophere. I worked at a refinery during college (~30 yrs ago). They changed their base blend 4 times a year.
All true. Great post. Again, there is no way to cover this completely and stay on topic. It would need a thread of its own. And then....we would have a bunch of *** clowns chiming in with myths and conjecture claiming to be the gasoline fairy.
Newtons3 is offline   Reply With Quote
Unread 08-15-2013, 08:21 AM   #443
Newtons3
Registered User
2006 TJ Wrangler 
 
Join Date: Feb 2013
Location: Baton Rouge, Louisiana
Posts: 723
Speaking of myths and conjecture... Does anyone have any thoughts or experience with the acetone legend? My first thoughts were to dismiss it as bs but then I thought -Ive doctored a bunch of fuel in my day (allegedly), there might be something to this.
Newtons3 is offline   Reply With Quote
Unread 08-15-2013, 08:35 AM   #444
ECL
Registered User
1998 XJ Cherokee 
 
Join Date: Dec 2005
Location: Easton, Pennsylvania
Posts: 223
Point taken - back on topic.
"Back in the day" (ie - those college days ~30 years ago), I'd put some cardboard in front of the radiator. This made the car run hotter, giving me a little more heat out of a paritally plugged heater core.
This has me thinking now. I assume all the Cherokees have my set up of a mechanical fan on the passenger side of the radiator and an electric fan on the drivers side. For those of us in colder climates, why not just put some cardboard in front of the radiator on the mecanical side? Some trial and error involved to figure how much to cover up. Might even want to increase the coverage deeper into Winter and begin decreasing toward Spring. The theorectical advantages I see are:
1) increase engine temperature and do so without having to open up the cooling system
2) effectively create some aerodynamic blocking, similar to the grille covers mentioned earlier in this thread
Has anyone tried this?
I think I'll experiment with this when it gets cooler.
ECL is offline   Reply With Quote
Unread 08-15-2013, 12:05 PM   #445
Charley3
Web Wheeler
1999 XJ Cherokee 
 
Join Date: Mar 2013
Location: Western, WA
Posts: 2,821
Quote:
Originally Posted by ECL View Post
Point taken - back on topic.
"Back in the day" (ie - those college days ~30 years ago), I'd put some cardboard in front of the radiator. This made the car run hotter, giving me a little more heat out of a paritally plugged heater core.
This has me thinking now. I assume all the Cherokees have my set up of a mechanical fan on the passenger side of the radiator and an electric fan on the drivers side. For those of us in colder climates, why not just put some cardboard in front of the radiator on the mecanical side? Some trial and error involved to figure how much to cover up. Might even want to increase the coverage deeper into Winter and begin decreasing toward Spring. The theorectical advantages I see are:
1) increase engine temperature and do so without having to open up the cooling system
2) effectively create some aerodynamic blocking, similar to the grille covers mentioned earlier in this thread
Has anyone tried this?
I think I'll experiment with this when it gets cooler.
Obviously the topics in this post are meant for people in moderate to cold climates. I say that so people in hot climates don't think I'm recommending the following mods to them.

For a moderate climates these mods are helpful for efficiency. For cold climates these mods are VERY helpful.

===

Yes, grill covers are being used by some people (in moderate to cold climates) and it works. It would work even better if you replaced mechanical fan with an electric fan.

What I want is 205F stat, all electric fans (don't come on in Winter), and an adjustable grill cover that I can adjust per season. That combination would be awesome in Winter, Fall, & Spring. In Summer I'd remove grill cover.

These topics have been discussed at length earlier in thread many times, including pictures of a good looking homemade plexiglass grill cover.

Cardboard is ugly. You can do better. Your idea is correct and does work. Please find these topics and pics earlier in thread.

Msch772 posted a pic somewher earlier in thread of a home made plexiglass partial grill cover that can be adjusted to block more or less.
__________________
Sometimes I edit a post a few times to get it how I want it.
Charley3 is offline   Reply With Quote
Unread 08-15-2013, 10:07 PM   #446
Charley3
Web Wheeler
1999 XJ Cherokee 
 
Join Date: Mar 2013
Location: Western, WA
Posts: 2,821
How is the topic of Winter vs Summer gas relevant?

You can only buy the gas available in that season.

No matter which gas, the Jeep mods still help.

So how is the blend of gas relevant when you have to buy what's available?

Am I missing something?
__________________
Sometimes I edit a post a few times to get it how I want it.
Charley3 is offline   Reply With Quote
Unread 08-15-2013, 10:51 PM   #447
Charley3
Web Wheeler
1999 XJ Cherokee 
 
Join Date: Mar 2013
Location: Western, WA
Posts: 2,821
I can't remember if all this was said. If so, probably not in one post.

Narrower tires get signifigantly better gas mileage than wide tires.

Lighter weight tire/wheel combo helps a lot because rotating mass matters substantially more than mass on frame or body. Rotating mass is an important area to try to save weight. Though saving weight on body, frame, or gear matters too.

Lighter tires helps a lot. Read tire weight before buying.
If you compare the same brand/model/size tire in different load ratings:
P-metric tires are lighter and have less rolling resistance than Load C.

Load C tires are lighter and have less rolling resistance than load D.

Load D tires are lighter and have less rolling resistsnce than load E.
Lighter wheels help a lot. So I recommend aluminum wheels. Smaller diameter wheels are lighter. Narrower wheels are lighter.

The less knobby the tread, the better the gas mileage. Some of the best latest generation ATs have low rolling resistance and good traction, but all season tires have even less rolling resistance.

Some latest generation ATs have silica in tread, which reduces rolling resistance AND increases wet and Winter traction. Silica also helps tread last longer.
__________________
Sometimes I edit a post a few times to get it how I want it.
Charley3 is offline   Reply With Quote
Unread 08-15-2013, 11:08 PM   #448
Charley3
Web Wheeler
1999 XJ Cherokee 
 
Join Date: Mar 2013
Location: Western, WA
Posts: 2,821
According to various Internet sources that I've read, every 100 lbs of weight trimmed from body, frame, gear, or cargo increases gas mileage 1 mpg.

Rotating mass matters even more. So saving weight on tires and wheels is very helpful.

I experienced signifigant gas mileage improvement on my LJ Rubi when I switched to a lighter tire/wheel combination. It also signifigantly improved acceleration and braking.
__________________
Sometimes I edit a post a few times to get it how I want it.
Charley3 is offline   Reply With Quote
Unread 08-15-2013, 11:26 PM   #449
bobthecatkiller
Registered User
2000 XJ Cherokee 
 
Join Date: Feb 2011
Location: binghamton, newyork
Posts: 805
Quote:
Originally Posted by Charley3
According to various Internet sources that I've read, every 100 lbs of weight trimmed from body, frame, gear, or cargo increases gas mileage 1 mpg.

Rotating mass matters even more. So saving weight on tires and wheels is very helpful.

I experienced signifigant gas mileage improvement on my LJ Rubi when I switched to a lighter tire/wheel combination. It also signifigantly improved acceleration and braking.
So I alone decrease my milage by 1.5mpg.
Now we should start asking how much people weigh in "way is my mpg so bad" threads.
__________________
officer: What where you doing down by the river?
me: awww ahhhh awwww exploring?
officer: mudding?
me: yaaaaa.
bobthecatkiller is offline   Reply With Quote
Unread 08-16-2013, 08:18 AM   #450
Newtons3
Registered User
2006 TJ Wrangler 
 
Join Date: Feb 2013
Location: Baton Rouge, Louisiana
Posts: 723
Quote:
Originally Posted by Charley3 View Post
After thought...

Instead of me stating Winter vs Summer gas is not a relevant topic for hypermiling, I should have asked, "How is it relevant?"

You can only buy the gas available in that season.

No matter which gas, the Jeep mods still help.

So how is the blend of gas relevant when you have to buy what's available?

Am I missing something?
Well, first, be aware that fuel itself can be inconsistant between fill ups ame between seasons/altitudes. This may have something to do with better power/lower m4leage in the winter and take the focus off of some of the other causes. Secondly, it may be possible to make smarter decisions about where we buy fuel in the winter to better meet our goals. Thirdly, what if we could mitigate all of this? Gasoline is a blend. We could add something to the recipe.
Newtons3 is offline   Reply With Quote




Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.