better fuel milage

[jdemaris]

A suburban will never see 50 mpg, the laws of physics won't let it at the speeds and acceleration rates most Americans drive at.

 

I've got a 3/4 ton 4WD Suburban that gets 27-28 MPG when cruising at 70 MPH. That's 27-28 miles per American gallon - not Canadian/British Imperial. Originally it had a 6.2 liter diesel and got a best of 22 MPG. I later swapped a 3.9 liter turbo Cummins into it and gets 27-28 MPG. Ironically the 3.9 liter Cummins makes the same power and torque as the 6.2 liter GM/Detroit Diesel engine.

 

Considering a modern diesel in around 45% efficient, there's lot of room for better fuel mileage as technology improves. If my Suburban gets 27 MPG with a 45% efficient engine, then a 75% efficient engine would give me 35 MPG. A 90% efficient engine would get me near 50 MPG.

 

So yeah, I suspect 50 MPG isn't really possible with petro-fuel on this planet in the near future. Now, my 1981 Chevy Chevette gets 48 MPG and my 91 Volkswagen gets 50 MPG. But they are tiny.

 

A modern Subaru engine is probably in the ballpark of 30% efficient? So lots of room for improvement . . . but I wonder. Why the heck doesn't Subaru put in some better overdrive? All the Subarus I've owned have gearing from the 60s. Most engines run most efficient at 2000 RPM, not 2600-2800 RPM like many Subarus run at highway speeds.

[robm]

Sorry, anything over about 60% efficiency is not physically possible. Check out Carnot Efficiency on the internet.

 

Real engines are less efficient. If you are getting 45%, you are probably maxed out.

[subynut]

This always wondered me the AWD vs FWD, now in Holland you can get the impreza 1.5R with FWD only. It needs 6.1 liter/100km, which is 38.56 MPG for out of city. However, the 1.5R AWD is rated at 36.75 MPG (according to the same standards). These both are manuals. The 2.0 AWD manual is 34 MPG while the automatic is 35.6 MPG. So on the long go more efficient. The diesel version gets about 48 MPG. The STI only gets 28 MPG.

 

I personally get with my 1.6 AWD impreza station about 28 MPG on propane and about 33 to 34 on regular fuel. The propane consumption is over 2 years and the fuel over about 2 months (5x refil). My old 1991 FWD legacy automatic got 28 MPG over 5 year average!!! Including city driving and alpine holidays.

 

Ah, kinda wondered what the mileage of Subarus outside the US were. Just as I suspected, the AWD really eats into the mileage. Those 1.5s and 1.6s certainly get screaming mileage. Although, they probably have the power of the old ea81s and ea82s. Not fast, but they get great mileage! Just out of curiosity, whats the average speed limits over there?

 

I've got a 3/4 ton 4WD Suburban that gets 27-28 MPG when cruising at 70 MPH. That's 27-28 miles per American gallon - not Canadian/British Imperial. Originally it had a 6.2 liter diesel and got a best of 22 MPG. I later swapped a 3.9 liter turbo Cummins into it and gets 27-28 MPG. Ironically the 3.9 liter Cummins makes the same power and torque as the 6.2 liter GM/Detroit Diesel engine.

......snip......

A modern Subaru engine is probably in the ballpark of 30% efficient? So lots of room for improvement . . . but I wonder. Why the heck doesn't Subaru put in some better overdrive? All the Subarus I've owned have gearing from the 60s. Most engines run most efficient at 2000 RPM, not 2600-2800 RPM like many Subarus run at highway speeds.

 

Turbo diesels certainly help the the mileage department and their torque is awesome!

 

Subaru seems to keep the RPMs between peak torque and peak hp. Which probably allows best mileage for the wide range of speeds we have in the States. The PandaWagon could certainly do 55 at 2000 rpm, but I don't think it could hold 75 at 3000 rpm - not without alot of throttle.

[rverdoold]

Ah, kinda wondered what the mileage of Subarus outside the US were. Just as I suspected, the AWD really eats into the mileage. Those 1.5s and 1.6s certainly get screaming mileage. Although, they probably have the power of the old ea81s and ea82s. Not fast, but they get great mileage! Just out of curiosity, whats the average speed limits over there?

 

Yes the 1.6 is not fast at all. It only really wakes up way after 3500 rpm. But I became a slow driver with fuel prices over here and shift at 2400 rpm to the next gear. Speedlimits are 20 and 30 MP/H inside the city, then we have a lot of 37 zones (farm and country roads often loads of wildlife and clay on the road from agriculture AWD helps a lot on these surfaces). And the main out of city roads are 50 MPH. Highway as in interstate like highways vary between 50 and 75 depending on area and traffic density. I generally cruise at 58 to 64. With the flow of the main traffic. Additionally holland is flat!!!!

 

I think 40% of the cars here are sold in US as small car (golf, opel astra, i30) and maybe an other 50% is smaller than that!!! There are not so many big cars over here. Due to CO2 rules, road taxing and emission based tax system.

USA like pick-up trucks you hardly see, only ford ranger and nissan navaras. WHY? go and fill it up at the gas station!! The main reason why I drive propane is because it costs about (all in euros) 60 cents per liter for 12 km, while regular costs 1.65 euro for about 14 kms. Ok the fuel tax difference are 194 per 3 months for propane against 112 for regular fuel. But the half price per liter is enough to drive on propane. Is it popular NO, idiots think you can only cook on gas. And most new cars can not run on propane because of the soft valve rings in the cylinder head. Subaru has no problems with it, but toyota no model can be converted and from most other brands only 1 engine type. That is why the new small turbo diesels are popular, however studies showed that these small motors ar not as durable as the old ones. Saving weight make the heads crack earlier (100k miles).

[rverdoold]

Subaru just launched the new XV in Holland with the new 1.6 (not even direct injection) and for a relative high standing small SUV it has a fuel milage of almost 43 MPG for the CVT. The diesel CVT even gets 47 MPG. Those are the numbers we would like the see!!.

The 2.0 has the same MPG as the 1.6 only more power

http://subaru.gillz.nl/files/spec-sheet-en-colors.pdf

[9098]

Non-Ethanol Fuel! 21/28 to 25/34

 

http://pure-gas.org/

[afterbang]

there is a station along my commute route that has 92 grade ethanol free gas. if it's worth the extra cost, I'm totally for it. Any more insight on the subject from EJ drivers? found some stuff on the old gen forum. if I can improve the gas mileage on my outback and is easier on certain parts (per what ive read is claimed), id go try it out.

[propane]

Good list- like the hub cap coverings- better dig out the remaining 3 of 4 mini caps for the OEM alloy ,1991 legacy LSi & add waxing the finish. drop off for fuel economy due to drag is around 65mph.

From local wrench radio, fill the tank slowly, as less “higher end” gasoline components, (volatile) will escape. You paid for ‘em might as well try to keep in tank to burn along other evaporative recovery fumes.

best ranking is tire pressure, syn oil or at least API “sunburst “ logo- fuel econ is a component to attain that rating, look for on oil container.

Agree that Carnot efficenticy is the wall, regenerative braking, heat recovery energy to DC elec, turbo in series, replacement of HP consuming ancillaries such as AC, PS,with electric (superchargers as well) will continue the gradual increase of MPG of the Ice (internal combustion engine) Age

[subaruplatt]

A suburban will never see 50 mpg, the laws of physics won't let it at the speeds and acceleration rates most Americans drive at. You're talking a 6000lb brick you're shoving through a fluid that does not want move out of the way. Now, with a small six, CVT, lowered, removed mirrors and roof rack, belly pan, and do no more than 50mph, you might see 40 mpg with a tail wind. However, do you really want to be the slowest SUV on the road?

With the technology we currently have, Mars is about the distance we can go. Just as the Moon was the farthest we could go back in the sixties. This is the bleeding edge of technology, which takes over the top funding to supply the equipment, knowledge, personnel, and time needed to do projects like these. Ever calculated the difference .1 degrees makes of where you end up at a distance of a million miles?

Until (or if) scientists figure out how to get to and beyond the speed of light, we are stuck with go fast and use more fuel or go slow and use less fuel.

We Americans are speed demons. We want to go fast, turn fast, go anywhere, and haul anything all a the same time while spending as little as possible at the pump. It doesn't work that way. If we want good mileage, we first must slow down.

Our Subarus are all weather vehicles - We sacrifice mileage for traction and stability. If you are a Subaru freak, like myself, then you must build a high mileage Subaru by sacrificing the all wheel drive for FWD, use the most efficient Suby engine out there with a tranny that has a good overdrive, and put it into the lightest and most aerodynamic shell Subaru built. The reality question is: If you are getting an average of 10 mpg more than a stock Subaru, how many miles will you need to drive that car to make up the cost of building such a high mileage Subaru? Is it cost effective? Probably not, but it would be a fun project!

 

 

 

Forgot to mention Saftey! These things hold up well in a crash, at least mine did.

[952.2LX]

Has anyone had experience with Hydrogen on demand for use in Subaru's? I've seen some claims that using hydrogen on demand drastically improves mileage.

[MilesFox]

remember that calculating fuel economy for awd vs fwd, is that fwd has a taller final gear. This is a factor more than the rolling resistance of the etra parts.

 

removing the roof rack would help more than ditching the jack and spare tire.

 

weigh and momentum is a factor when accelerating, but overall aerodynamics makes the most difference at highway speeds.

 

ditch the passenger mirror, go with low profile woper blades, and flat hub caps, air up the tires within 10% of max.

[subynut]

I was looking at the owner's manual for the PandaWagon (87 Wagon) and the 2WD does have a slightly taller final drive, but the tires (175/70R13) are shorter than the 4WD tires. So, I wonder how much of a difference is there in RPM? Anybody know what their RPM at say, 65 is in a 2WD? I know it was about 3K in my 86 carbed wagon with a PT 4WD manual.

 

What's more interesting, I was looking at the gear ratios in the XT/XT6 FSM and the 4WD auto has a 3.7 final with a 205/60R14, but the 2wd auto has a 3.9 final with a 195/60R14.

 

I also found (somewhere on nasioc) the 2WD impreza has a taller 5th gear with, I think, was a 3.9 final. Whereas the 2WD Legacy has a 5th and final cloaser to the 2WD EA82. Now, I did not check tire sizes, could be the Impreza has a shorter tire than the Legacy. Hmmmmm...

 

"Lefou, I'm afraid I've been thinking,"

"A dangerous pastime.."

"I know."

 

[SchwarzeEwigkt]

This thread is starting to sound like a hypermiling club. How long before we see stuff like this boat-tail Geo Metro going on in here?

 

 

It's always heartwarming to see what people will do to keep their Scoobs around and keep them from eating them out of house and home.

[cal_look_zero]

I used to always draft semi trucks in my old VW. The most obvious benefit was that I could actually maintain freeway speeds. The local ski area is about 8 miles off the freeway. I would draft a semi all the way to the off ramp, and drive up at a normal pace. Dual carbs would never run at the elevation after being cold all day, so I would push the car out of the lot and coast all the way back to town.

 

74mpg... does it count if half the mileage was coasting with the car off?

 

My Loyale gets 26ish mixed with stupid little tires, and the Legacy is only on it's 2nd tank, but I'm at about 19 mixed with an exhaust leak and probably dead o2 sensor. I have a heavy foot, and average about 75mph on the freeway to work and back. Couple of steep hills, and lots of left lane campers who throw off the pace.

 

My Montero gets around 14-15 and my Ford gets 12, so I'm not going to complain. I could have gotten a 38mpg 1.5l civic, but I like the idea of being able to go boarding before work.

[eulogious]

I truly wonder if you really save any MPG by using FWD instead of AWD. I will have to try it and truly see if there is a difference.

 

Since I have a modded TCU with paddle shifters and full control of my AWD, I can safely put my car into FWD mode for extended periods and not worry about destroying my Duty C. And even if I destroy my Duty C, I got a replacement trans already waiting for me to install it, so I don't got nothing to lose I will have to try this experiment over the christmas weekend. I have to drive up to Seattle and back, so I will do the whole trip once with FWD and once running it "normally". This will take me a couple of months to do, since after xmas, I probably won't be going away for a while. This way we can see if just running a subaru with the FWD fuse it actually saves on MPG. And as long as it doesn't get icy or rainy, I will try to use FWD mode for the entire tank to really try to see if there is a difference just running around town.

[subynut]

cal_look_zero:

Intersting, my 2002 F350 gets 11 mpg with the V10, 6sp manual and 4WD. The PandaWagon gets good milage, but not as good as it could be with my lead foot and non-operational cruise control. I really gotta work on that.

 

eulogious:

Even though there may not be that much of a difference in MPG since the rear driveline is still rotating, I still would like to see how running the AWD tranny in FWD would effect the amount of energy used.

[cal_look_zero]

cal_look_zero:

Intersting, my 2002 F350 gets 11 mpg with the V10, 6sp manual and 4WD. The PandaWagon gets good milage, but not as good as it could be with my lead foot and non-operational cruise control. I really gotta work on that.

 

eulogious:

Even though there may not be that much of a difference in MPG since the rear driveline is still rotating, I still would like to see how running the AWD tranny in FWD would effect the amount of energy used.

 

Not sure if you were directing that to the mistu or the ford, but I have excuses!

 

The mitsubishi, I "modded" it when I was 19 and had just gotten it. It's needed o2 sensors for awhile now, but at nearly $300 a set... bleh. I also put a short ram intake on it, or as I've known for awhile now, the "sucking hot air" intake.

 

The ford has a crappy 2bbl motorcraft carb that won't feed the 302 in the top end unless I have a richened fuel mix. I need to sack up and put a nice progressive 4bbl on there.

[subynut]

Yeah, that V8 should like having a 4bbl on it. We just don't want to go too big, otherwise it's mileage won't change.