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Old 06-06-2011, 11:11 PM   #1 (permalink)
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More ideas?!?!

We've all head the news stories about hypermilers who get 60 mpg in a normal, family sedan. Well I have a 1996 Subaru Legacy Wagon L and generally get pretty good mileage for the car (i.e. 30 to 32 mpg). I would like to improve this even further (hopefully close to 40mpg, ha). The following is what I have done to improve mileage. I also use a ScanGauge to track mileage.

-Basic Hypermiling
~Strong use of cruise control
~A lot of coasting
~Slow accelerations
~Reduction of stops
-Removed rear mud flaps (which were cracked and old)
-Tires properly inflated to 44psi
-Major rust holes in body have been removed and filled with fiber glass
-Never use AC
-Roll down windows at stops and use vented air while driving
-Remove unnecessary weight
-Replaced broken fog lights with dense foam for less weight and better wind resistance (similar to grill block)

What other things might I try to improve my mpg?

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Old 06-06-2011, 11:23 PM   #2 (permalink)
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Subaru's have alot of friction in their drive train so I would start there, I haven't looked at the underside of one, but it seems like it would be well worth checking out for improvement.
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Old 06-06-2011, 11:30 PM   #3 (permalink)
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Appreciate the info. How would you improve the drive train friction issue with a Subaru? I'm not familiar with that issue in cars.

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Old 06-11-2011, 12:40 AM   #4 (permalink)
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You're doing pretty well! Do you have a manual or an automatic transmission? Under the same conditions, a manual will typically result in an instant 10-15% gain. I had a 26 mpg lifetime average with a stock 96 Legacy L wagon automatic (including winter) and typically got 27-29 mpg in the summer - until upgrading to an 05 Legacy 2.5i manual a few weeks ago. I now get up to 32-34 mpg in mixed driving.

With either transmission, you save fuel by downshifting when going downhill or approaching a stop, since when the engine is in gear with the gas pedal released it will use no fuel at all. I've noticed no difference in fuel consumption with the windows down, even at highway speeds - but there's an instant drop on the mpg display as soon as I use the AC.
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Old 06-11-2011, 04:47 PM   #5 (permalink)
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My suggestions :

- Tyres as inflated as sidewall max less 5psi at first. This helps reduce drag without affecting grip - in fact grip may improve. Try it though, your car may be different and it is your responsibility to be safe - e.g. wet weather makes roads 50% as grippy as dry. If you are happy go to max.

- Less use of cruise - it maintains a set speed no matter what, and maybe you don't need to - see below.

- Driving with load, or rather driving to an MPG. Set yourself a target MPG and try to stay over it. Put AVG together with MPG on your scangauge - if you keep MPG > AVG then you are improving.

- Combine this with a minimum safe speed so you don't get in people's way or where you can pace / follow the trucks in the slow lane.

- At the same time don't panic if your instant MPG goes lower as you will hit a peak on any journey and then it will be hard to improve. In these circumstances try to maintain MPG as high as possible.

- Don't be afraid to use topology and traffic. For example in rolling country use the downhill sections to gain speed to use on the next incline, or use the decline to EOC. In traffic coast when you can and leave a gap in front so you can cruise if the line stops. Forget fretting about people pushing in - who cares, it costs them more in $s than you, and it makes them 0% better than you overall

- Check if your vehicle EOCs OK - i.e. if you go downhill in gear does your fuel shut off - does your MPG go to infinity... (or 999.99). Most FI engines shut off fuel when decelerating in gear (i.e. on overrun) but will still idle if cruising out of gear. You need to decide when and where to use which technique - on downhills use a high gear but remember the compression in your engine will slow you down, on the flat use neutral as you coast longer.

- If you are using an Auto then out of gear is probably your best option - check your car is OK to coast out of gear or can lock up in top.

FWIW and IMHO Subarus are not the most FE friendly vehicles. For a start there is the extra weight and drag of the AWD system and secondly I don't think the flat four is a really great engine for FE.

Even the Diesel one in Europe which has the latest tech - CR injection, variable Geometry turbo - does no better than any other CR direct injection Diesel even of a few years ago, although IMHO again Japanese Diesels are a generation behind those of Europe.

Add to that the oil starvation issue (the top half of the flat cylinders is left dry when the oil drains to the lower half when the engine is stopped) - TBH I would avoid them.

Just my thoughts, but good luck.
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Old 06-11-2011, 08:21 PM   #6 (permalink)
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Quote:
FWIW and IMHO Subarus are not the most FE friendly vehicles. For a start there is the extra weight and drag of the AWD system and secondly I don't think the flat four is a really great engine for FE.
You're right about the AWD system adding drag, but there is nothing inherently inefficient or unreliable about the flat-four engine. The current Legacy gets mileage on par with comparable FWD cars, and reliability issues with Subaru engines in the past have been generally unrelated to the flat-four design itself. The 2.2 in the 96 Legacy is not quite as efficient as newer engines, but it's a bulletproof engine that will easily outlast the rest of the car.
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Old 06-12-2011, 12:48 AM   #7 (permalink)
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trainiax -

Quote:
Originally Posted by trainiax View Post
You're right about the AWD system adding drag, but there is nothing inherently inefficient or unreliable about the flat-four engine. The current Legacy gets mileage on par with comparable FWD cars, and reliability issues with Subaru engines in the past have been generally unrelated to the flat-four design itself. The 2.2 in the 96 Legacy is not quite as efficient as newer engines, but it's a bulletproof engine that will easily outlast the rest of the car.
That's why I wish Subaru would offer FWD or RWD versions of their cars for MPG. That gorgeous little boxer engine never gets to flex it's MPG muscles.

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Old 06-12-2011, 05:26 AM   #8 (permalink)
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I looked at a Forrester a few years ago after my first winter in Scotland but it didn't sound quite right so I checked with HJ.

Quote:
EJ20 two litre Subaru engines (and some others) developed a bad reputation for premature big end bearing failure. Subaru is claimed that the problem was lack of maintenance, but a number of cases where the buyer was careful and thorough
and it still occurred. The problem is worst on the twin turbo versions: these engines are equipped with the short skirt pistons which also wear badly. The symptom of the big end problem is a distinct knocking when you start the car from cold and the symptom of the piston wear is a rattle when cold. The above two problems seem to strike at around 100,000 miles.
He doesn't mention it on later cars though.

It will be interesting to watch what happens with FE and I hope it turns out to be at Hypermiler status. I just wonder if the flat 4 is that efficient compared to say a similarly sized "Camcorder" or equivalent Hyundai / Kia.

EDIT - Anyway, this is taking the thread to Cuba

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