My goal is to get 25+ mpg from my 99 XJ with 30 x 9.5 R15 ATs - Page 26 - JeepForum.com
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Unread 08-11-2013, 10:45 PM   #376
titomars
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Quote:
Originally Posted by infob View Post
Body is real nice on it though... That would probably be the major difference in cost from there to here... Anything with 4 wheel drive has been offroad... Not saying everything here was jumped over rocks or anything just that they tend to have a dent or two here and there and the tell tale scratches down the sides from them pesky thorn bushes
Yes its really straight and the paint is decent but the 4 corners of the roof is rotted out. I just ground them down to shinny metal and filled them with bondo and primed it.

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This is the kinda whiny crap I would expect to see in the JK forum. We drive rough riding, leaking, gas guzzling CJ's. Rattle can it and throw it in your Jeep.
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Unread 08-11-2013, 11:09 PM   #377
Charley3
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Originally Posted by silentneko View Post
Yes you are in fact only matching your stat to your colder climate, and this is the kind of information you should have relayed upfront before anything else. So in reality you have not increased your fuel mileage at all, you have just gotten your jeep to run at normal operating temps.
Somewhere way earlier in this thread I posted that a hotter stat in my current Jeep, like two prior Jeeps, and in a Dodge car, and in my Buick, allows my engine to run same or similar temp in Winter as it already did in Summer with stock stat. That imples I need the warmer stat to reach full op temp in Winter (and Fall and Spring). I didn't explicitly emphasize that I'm in a Northern climate, but my profile says WA, which is obviously a Northern state.

In hindsight a better way to say that would have been: A 205F stat allows me to run at full op temp year round (in a Northern climate).

The 205F stat is a huge benefit in cooler climates. Just as electric fans are a huge benefit in cooler climates. They are ideal in Winter here and OK in Summers here since we only see 90s occasinally, and only every few years see 100F. This Summer is cool enough (mid 60s to high 70s most days) that I need a 205F stat to reach full op temp even in Summer.

It was already widely known that elecric fans offer little (if any) benefit in a hot climate.

Now we have learned from you and Newtons that there is no gas mileage benefit from a 205F stat in a hot climate because your engine was already hot enough with stock stat. You didn't know that about your very hot climate until you tested it. How could I have known that when I've never lived in a hot climate? That's why we test things. Now we know.

You claim I didn't inform you this wouldn't help gas mileage in your hot climate. I didn't know. I only said it helped me, especially in Winter, and my profile clearly states I'm in WA State, an obviously Northern state.

I really only ever claimed the 205F stat helps my XJ and my other vehicles, which it has. Obviously in my climate. In hindsight, the climate part is important. The warmer stat and electric fan(s) mod is good for me in a Northern climate, and I think would be good for others in a Northern (cooler) climate. Those mods have never caused me any problems in 20 years doing them (in my Northern climate).

Now we know those two mods are NOT recommended for Southern (hot) climates.

Southern Jeep XJ and TJ hypermilers don't give up. There are many other mods in this thread that are suited for all climates, and a few mod specifically suited to hot climates. However, another mod not suited to hot climates is blocking off part of the grill. Grill covers are only good for cool to cold climates (where they are good).

Quote:
Originally Posted by silentneko View Post
There has been some discussion on this thread about how the hotter engine temps might end up destroying your transmission, but there has been nothing said about your other components. I am pretty positive that the sustained hotter engine compartment temps caused the failure of my A/C system yesterday.
There is only one way I can see hotter engine temps reducing your gas mileage. Hotter might reduce gas mileage if engine constantly hot enough to keep your mech fan clutch fully engaged and your electric fan running often. I could see that might reduce gas mileage some.

I warned about this in an earlier post in thread where I said hotter is better to a point, but you don't want it hot enough to make your stock fans work harder.
My engine doesn't get hot enough (even in Summer) to make my electric fan come on more than 1 to 2 minutes per week (in Summer). I'm not sure if that's my 205F Gates stat possibly being slightly cooler than your 205F ACDelco stat, or if it's my heavy duty tow package radiator, or my tranny cooler, or my climate. Maybe all those. I posted earlier in thread that with stock fans I want the hottest stat that doesn't make the fans work harder (because if fans are working harder, they use energy, which burns gas).

So warmer is only more efficient if it's not constantly triggering mech fan clutch and electric fan sensor to come on. i.e. - warmer is more efficient to a point, but if it's triggering your fans to run hard all the time, it's to warm. I did say all that much earlier in the thread. Obviously climate is part of the equation, as has been called to our attention.
I'm sorry you're having problems with your AC. Since I seldom need to use my AC, I never put any wear and tear on the AC system. Also, my XJ never runs above 210F, except for occasional, brief 1 to 2 min visits to 215F during long slow 3 mph hill climbs on out hottest days here (80s).

So I am not qualified to comment on the AC. I would be interested to know what the repair people say about it. I read where Newtons said he thinks your AC problems are unrelated to your 205F stat. Newtons is a professional mechanic, race driver, and cudtomizer. He is knowledgeable.

I read where you said your brakes felt weak. I do not beleieve that could have anything to do with the 210F to 215F engine temps you've described. On a 96 XJ I used to own, for 1st year I owned it, it had a small one core radiator and a defective electric fan switch. With the stock 195F stat it ran 215F to 220F most Summer days, and 230F when off road in Summer. Engine was hot like that for an entire Summer (and we were having an unusual high 90s and 100+ heat wave for weeks that Summer) and it never hurt a thing in the engine or tranny or anything else, and my brakes were fine. I think you either got paranoid and imagined brake problems, or if you really do have brake problems, it is unrelated to 215F engine temp. IMO

Sorry about your AC, but Newtons said it's probably unrelated to 215F engine temp. In any case, hope it gets fixed and works out well.
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Unread 08-12-2013, 12:31 AM   #378
Charley3
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So in light of recent posts, let me say this here in its own post.

Most mods in this thread would likely improve your gas mileage in any climate.

However, the following specific mods are only for cooler climates, such as Northern USA and Canada:
1) 205F thermostat

2) Mechanical to electric fan conversion

3) Partial covers

4) Oil warmer - Mschi suggested earlier in thread
Having said that, I have found the 205F stat (on several Jeeps and others cars), electric fan(s) (on prior Jeep and my Buick) to be effective in my Northwest USA climate, which varies from moderate to slightly cold. I am certain a partial grill cover (in Winter) would help (because others have proven this in cold Winter climates). I haven't tried the oil warmer, but it sounds promising to me (for moderate and cold climates).

I think those 4 mods would be even more effective in the even colder climates of Northern Midwest, Northeast USA, Canada, and Alaska.
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Unread 08-12-2013, 01:07 AM   #379
Charley3
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The 205F Gates thermostat has been great for my XJ in my moderate climate. It'd be even better in a colder climate. I'd expect the same for any 4L Jeep engine in a moderate to cold climate.

The 205F ACDelco thermostat might be good for 4L Jeep engines in moderate to cold climates, but I haven't tried it. I don't know anyone who has tried it in a moderate to cold climate.
Based on preliminary reports it seems the 205F ACDelco stat MIGHT be slightly warmer than the 205F Gates stat. If that is correct, then I'd recommend the ACDelco stat for cold climates, the Gates stat for moderate climates, and stock Mopar Jeep 195F stat for hot climates.

As soon as possible, I am going to buy another 205F Gates stat and a 205 ACDelco stat so I can test them in a pot of boiling water to see which opens first. Based on what people have posted about using these stats in their Jeeps, I expect the Gates will open at a slightly lower temp than the ACDelco. Testing side-by-side in a pot of boiling water will tell us for sure which is the warmer stat.
Don't install a 205F stat if you live in a consistantly hot climate.
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Unread 08-12-2013, 04:33 AM   #380
rebelbowtie
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Quote:
Originally Posted by titomars

Actually I am looking for one. I want a nice 91 to 94 2dr 4.0 with AX15. I don't care if its 2wd or 4wd, either way is fine. I will consider newer than 94 but ideally I prefer to have a non-airbag one. My 4dr is eventually donating it's engine to be a stroker in my CJ.

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Unread 08-12-2013, 05:51 AM   #381
ECL
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Anybody ever play around with aerodynamic mods? Specifically I'm thinking about the front spoiler. I'm wondering if extending it with a piece of rubber landscape edging would decrease the amount of air flowing under the body yet also be flexible enough to not cause a problem off road. Just a thought...
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Unread 08-12-2013, 08:19 AM   #382
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Yes, I have. I think that a bellypan would be more effective than extending the front air dam unless you drop the Jeep to where its only 1/2 inch off of the ground. Ive done stuff with the bumpers, nose, wheels/fenders, and roof also.
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Unread 08-12-2013, 02:01 PM   #383
Charley3
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Here are some other climate dependent mods.

Earlier in thread guys from hot climates suggested hood louvers/vents, or spacing up the rear of hood, to allow hot air to escape and lower under hood temps and they claimed this improved gas mileage. I believe it.

In a chronically hot climate that makes sense for a few reasons. It would lower under hood temps to a reasonable op temp, which would be easier on compnents, and the cooling fans would not need to work as hard.

The mechanical fan's clutch wouldn't need to be engaged as often, and the electric fan wouldn't need to come on as often. That would reduce energy consumption and increase gas mileage.

Also, allowing air to escape from top side of hood reduces wind resistance when driving at highway speed because (as with positive rake) the top side of vehicle is much smoother than underside. So redirecting air over vehicle, instead of under it, increases aerodynamics.

So I can see why people in hot climates like hood venting mods and why some of them claim a vented hood improves gas mileage. I believe it, but only in a hot climate.

In a cold climate, I think a vented hood would decrease gas mileage.

In a cool climate it's a struggle to get engine to full op temp of 210F, even in Summer, and much more ditficult in Winter. In Winter, a stock XJ in my area runs at 185F to 190F and guzzles gas.

So I would not want a vented hood. In my Northern climate I want to retain under hood heat and raise engine temp to full op temp of 210F because more fuel efficient at 210F than at lower temps.

So no hood vents for me in a Northern climate. Instead, in a cooler climate I want a warmer 205F stat for year-round, and a partial grill cover in Winter and colder half of Fall and Spring. The partial grill covers helps two ways (in a cool climate). It helps engine reach full op temp, and it reduces wind drag by keeping unneeded air flow from entering grill. i.e. - improves aerodynamics.
Grill covers were an idea presented by someone from the North. I like the idea (because I'm in a Northern climate).
To avoid making my fans work more, I've been careful to avoid running hot enough to make electric fan come on more than occasionally. Since electric fan comes on at 215F, running at 210F is ideal. 210F is hot enough to be ideal for efficient burning of fuel, and cool enough that fans don't work hard.
Running hotter than 210F (215F stat) MIGHT further increase fuel economy, but only if you have all electric fans (no mech fan) and a fan controller that makes fans come on at a high enough temp that the fans seldom come on. I'm not ready to go this far at this time. For me, for now, 210F is good because it is warm enough for engine, and cool enough to be efficient with my stock fans.
Replacing mechanical fan with electric is a waste of time in a hot climate, but in a cold climate is very effective at improving power and fuel economy. This is because in a cool climate, electric fans seldom come on because they are seldom needed. Also, engine warms up faster and warmer.

Mschi's oil warmer idea has merit in a cool climate. I want to try that.

---

The other fuel economy improvement ideas presented (by myself and others) in thos thread are not climate dependent. For examples, wind skirts on lower sides of vehicle would help aerodynamics in any climate. More tire pressure, good alignment, less weight, and a whole list of things (mentioned earlier in thread) would each be helpful in any climate.

---

But from now on, when any of us presents a gas mileage improvement mod idea, we should think about if it's for a specific climate, or for any climate, and mention that.
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Unread 08-12-2013, 04:08 PM   #384
Newtons3
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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.
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Unread 08-12-2013, 05:41 PM   #385
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Here in the Northeast we have a winter gas blend which also hurts mileage. I believe it is a different blend to help with emissions, but all of the vehicles I'm around get 2-3 mpg worse when using winter blend fuel.
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Unread 08-13-2013, 02:48 AM   #386
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The difference between winter gas and summer gas is the volatility. Summer temps turn liquid gasoline into vapor easily, whereas winter temps do not. That's why there's a winter blend. It's cheaper and more volatile so our cars can burn it in the cold. It really is a garbage product designed to be burned quickly, thus the decrease in economy. Not specifically emissions related.
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Unread 08-13-2013, 04:20 AM   #387
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Where I do find most of the general statements about winter gasoline to be true in principle, I think it is unwise to lay all economical changes off on gas when there are other variables at play also. I also have to dispute the figures commonly tossed around because they would indicate a drop of 25 percent or more for some people. Instead, Id rather see a true percentage change with consideration for all of the other things that affect mileage - warm up time, travel in snow and ice, colder IAT, cooler operating temps, etc.
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Unread 08-13-2013, 06:53 AM   #388
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More data points about winter fuel here in the Northeast:
1) Several years ago I drove from Easton Pa to Wheeling WVa in my old Buick Roadmaster. Dead of winter. Bought gas in NJ the night before. Did not make it all the way out before having to fill up again. On the return trip (a few days later), I made it home and went to work the next day on the same tank.
2) My son routinely couldn't make it to State College Pa (Penn State) on one tank of NJ gas in his YJ but could make it home on one tank of gas from out there.
3) Drove my daugher to Blacksburg Va (Virginia Tech) last year after spring break, 420 miles each way. Thought it would be a good opportunity to experiment. Bought NJ gas the night before. Drove 70mph down and back on cruise, no AC on either way. Trip computer in our new-to-us '08 Volvo V70 wagon showed 26MPG going down. Filled up down there. Coming home but the trip computer showed 32 MPG. Obviously we were lighter coming home but not enough in my mind to justify a 6 MPG difference.
Bottom line to me - winter "smog" fuel here just isn't as good.
As a side bar, we did a family trip in a '05 Volvo where we picked up our daughter in Blacksburg and went to Florida. Summer time and another good opportunity for an experiment. Used regular going down and premium coming home. Kept all the receipts. Trip computer showed 24 MPG going down and 26 MPG coming home. After running the numbers, the cost differential to buy premium didn't justify the 2 MPG improvement.
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Unread 08-13-2013, 08:27 AM   #389
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Cool. Good info. Do you know of any oxygenate differences? That could make a considerable difference too. Heavy smog areas here require more ethanol which means less mileage by about 5-10 percent.
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Unread 08-13-2013, 08:59 AM   #390
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Unfortunatley not.
Pumps around here have a sticker saying "up to 10% ethanol" but we never really know how much. I don't recall if the pumps in the other places had stickers saying anything about the ethanol content.
I dont know about if anything else is added to oxygenate - I've always assumed the ethanol is what "oxygenates" the fuel. If I remember my chemistry correctly, ethanol is ethane that has been "oxygenated" into an alcohol by adding an oxygen atom. Specifically, if I remember this correctly, one of the hydrogen (H) atoms in is replaced with a hydroxol (OH) ion. This process effectively partially oxidizes or "burns' the molecule and that's why alcohols are less energy dense than gasoline blends. Maybe someone here who more recently learned this could clarify or correct me.
PS - Again if I recall correctly, gasoline contains a lot of "...ane" series hydrocarbons - methane (CH4), ethane (C2H6), ...octane (C8H18)...(octane being a particuarly high percentage, which is why it is a good benchmark to measure a fuel's anti-knock characteristic to).
Ok - enough chemistry for the day...
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