Very preliminary (non-hybrid) SGII results: P&G, speed effects, accel, climbing

Discussion in 'Fuel Economy' started by WriConsult, May 30, 2007.

  1. WriConsult

    WriConsult Super Moderator

    Just got my SGII working yesterday and wanted to get a baseline idea of the Outback's FE in various situations. Took it out for some preliminary 1 mile runs with the SGII on a flat, straight parkway near my home last night. These are single run results so they need to be taken with a huge grain of salt. Also, these are unadjusted readings so they could be substantially off, but the relative resuls are certainly still useful. Once I have more consistent, reproducible results I'll post again. Still, I think I've learned some good stuff here.

    • Steady 25 mph: 42 mpg.
    • Steady 40 mph: 44 mpg.
    • Steady 45 mph: 41 mpg.
    • Steady 50 mph: 37 mpg.
    • Steady 55 mph: 35 mpg.
    • Moderate P&G, 35-45 mph: 53 mpg (!)
    • Moderate P&G, 40-50 mph: 44 mpg.
    • Heavy P&G (strong acceleration in 5th), 40-50 mph: 35 mpg.
    I need to get some 30 and 35 mph runs in too, because it looks like my mpg peak is going to be somewhere in the mid to high 30s. Again these are single run results so admittedly there's quite a bit of statistical uncertainty, but I'm really struck by the results of the 35-45 P&G. Even the 40-50 P&G got the same mpg as a steady 40, while averaging 5 mph faster. Conclusion: Pulsing and Gliding looks like it can save a lot of fuel.

    I also tried a few acceleration runs: very light Grandma throttle to 2k rpm, moderate throttle to 2k, moderate throttle to 3k, and full throttle to the 6.5k redline. I didn't get very consistent results, but it appears that moderate throttle with shifts at 2k gives the best mpg. That's mirrors what others have said on this site, and it's pretty much what I've been doing since I started attempting hypermiling.

    Finally, I also experimented a bit with various throttle and gear combinations on a long hill on the way home from work last night. I've generally been doing this hill in 5th gear at about 35 mph, which the car can just barely do at about 1/3 throttle without lugging. Downshifting to 4th and maintaining the same speed increased the fuel consumption by 20-40% (again, my numbers aren't very solid yet), which doesn't surprise me.

    What did surprise me, though, is that if I stay in 5th and floor the throttle to push the engine into serious lugging territory, the fuel consumption only drops very slightly! I've always assumed that lugging is really bad for FE, but at least on my car it doesn't appear to cost me anything. For climbing, the optimum appears to be to be in the 1500-2000rpm range and at the point where the engine is not quite lugging. Basically what I've already been doing the last few weeks.

    Finally, I'm surprised by the low fuel consumption figures at idle: generally 0.2 or 0.3 gph. That's about half of what I assumed I used while idling. When I'm coasting at any speed above 30 mph, it's amazing to look at the display and see instantaneous mpg figures in the 100-250 mpg range with the engine running. So the finding here is that coasting, even with nICE-ON, has enormous benefits (hence the excellent P&G results above). FAS has some additional benefits but they appear to be incremental in my case. My calculation is that if I can FAS for 5 minutes of my 1 hour, 30 mile round trip commute all the way to work and back, that will improve my FE by about 0.5 mpg. Still worth doing, in other words.

    I think the big takeaways for me are:
    • Keep doing what I've been doing in terms of acceleration, climbing and FASing.
    • I'll probably do the above more consistently now that I've confirmed them.
    • Coast whenever I can, including Pulsing and Gliding whenever it makes sense. I already P&G some already, but there are lots of P&G opportunities I'm not yet taking advantage of.

    Lots more to learn, but I can't wait to apply this stuff and shoot for 30+ mpg. Are these results consistent with what others have been seeing in their non-hybrids?
    Hopefully I can get my average up over 30 mpg!
    Last edited: May 30, 2007
  2. brucepick

    brucepick Well-Known Member

    I'm sure you'll achieve 30 mpg, based on your first two tanks at roughly 28 and 29 mpg. Looks like you're just getting started so I'd guess you might get your overall up into the low 30's - or better!.

    I sure appreciate your posting this.
    My '89 Volvo has a 2.3 engine and similar weight to your Subie (maybe a bit less than Subie).

    Your results tell me I've been on the right path: lots of coasting in neutral, and P&G with moderate acceleration. My auto tranny usually wants to keep engine at 2K or above however, so that's what I'm working with. Seeing the P&G data is very instructive.

    If you haven't already, consider the below to help with FE:
    max sidewall tire pressure
    synthetic oil
    lowest weight oil allowed for your climate by owner's manual (less resistance to the pump)

    Good luck!
  3. WriConsult

    WriConsult Super Moderator

    My Subie comes in right around 3050 pounds (I know this because I always look at the readings on the receipt when I haul a load of stuff to the dump). Should be extremely close to an '89 245 wagon. My wife had an '84 245 gas wagon before her current 244 diesel sedan, and I think it was within 50 pounds of the Subie.

    Already done. Seems to improve cornering in dry weather, but can get really sketchy in the wet. Not sure I'll have the guts to keep the psi quite so high when winter rolls around.
    I've heard switching to synthetic in an older engine (mine is at 140k) can stir up sludge and cause problems. Any issues on your car when you switched?
    My mechanic did the last oil change, so I'm not sure what's in there now, but when I change it myself I always put in the recommended 5w30. I've seen 0w-30 synthetic in the store: that should be OK as long as the second number is the same, right?

    Thanks for the reply.
    Last edited: May 30, 2007
  4. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Welcome, WriConsult!

    What you've posted looks pretty good to me, though if you get into FASing I think you'll find yourself using it quite a bit more than 5 minutes out of an hour.

    I'm relatively new myself, but I'm pulling segments of over 50mpg in my car (rated for 33mpg on the highway) -- and the average speed is around 40. Most of the driving I do is on the highway with posted limits from 55 to 65mph. Using pulse and glide with FAS for the glide component is what gets the number that high for me -- and I would guesstimate that I'm FASing around a 3rd of the time I'm on the road? For comparison, I start out on slow roads with the occasional stop sign and light, move to the highway, and finish up with similar conditions on the other end. The distance I pull high numbers on is 35.5mi or so. I might be able to do a similar job on the other trip I do often, but that is normally in the dark and my headlights turn off when I key off. I can't really FAS much when that happens!

    Keep doing what you're doing and keep an eye on that ScanGuage -- it will teach you a lot!
  5. jcp123

    jcp123 Caliente!

    Interesting comparo: my Dad had an '00 VW Passat V6 4motion wagon with the in-dash MPG display and got a steady speed peak of 42mpg @ 48mph. Just another example of how two vehicles in roughly the same category (Passat's bigger and heavier at ~3800lbs, but cross-shopped by some of the same people) can differ so broadly.

    As to running synthetic...I've head that if you have more than 60k miles on an engine that's never run synthetic, don't do it. Not only will you stir up sludge like you mentioned, you'll start oil leaks that will never, ever stop. I recommend you stay with dino oil, or else things will start getting very, very expensive.
  6. brucepick

    brucepick Well-Known Member

    Yup. I think the 240 wagon (aka 245) is 3030 or 3050 lb.

    I suggest as a site for oil information.

    I can only report my own experience. I changed to synthetic last summer, maybe 260K miles on the engine. I used a can of "Gunk" internal engine cleaner but did NOT drop the oil pan to clean it as instructed on the can, that's a major job. One or two months ago the engine did develop a leak in a flat gasket at front of block (metal timing cover plate, behind the belt cog wheels). My shop replaced gasket this week and so far it looks good. Don't know if it was related to the synthetic change or not. I switched my wife's similar 240 over to synthetic this past fall. No problems there either.

    See if your owners manual gives more than one option for oil weight. True, the 2nd # in oil rating is the one that counts once it's warmed up. However I'd also pay attention to the lower # as too thin an oil for the prevailing temperature can also be harmful. 5-30 might be OK at 60 deg F but not at 90. And this summer you'll start your car at 90, right?

    One thing I learned from is that a narrower range of oil weights gives an oil that will hold up longer and better. That is, 10-30 will outlast 10-40 and will perform better at half-life and near-end-life. See 'bob" for details.
  7. brucepick

    brucepick Well-Known Member

    Re. switching to synthetic, I'd suggest
    Ask there, I'm sure they've been through the concerns about switching Subaru engines later in life.
  8. Dan

    Dan KiloTanked in post 153451

    That statement alone proves that your definitely in the right place :D

    Nice writeup, and 53 :eek: , what is that 192% of EPA or something like that?

  9. WriConsult

    WriConsult Super Moderator

    Looks like the ScanGauge is helping already. I filled up today, having hooked up the SG more than halfway through the tank, and it looks like this tank was good for 29.1. And the SG is telling me 31.8 mpg overall for the day yesterday and 32.4 today. Today's drive was over 100 miles, with a trip out of town for some mountain biking after work.
  10. Not trying to hijack the thread, but have a few related questions.
    1. it looks like the SGII doesn't work with most cars older tha 96, why is that?
    2. I was under the impression that you can't do FAS with out a hybrid, or at least a manual tranny, or am I confused?
  11. tbaleno

    tbaleno Well-Known Member

    1) it uses the OBD II specification that wasn't standardized until 96
    2) Depends on the transmission more than the type of car.
  12. brucepick

    brucepick Well-Known Member

    Can you be more specific about the ability to compute FAS with SGII - with different transmission types? Is it auto vs. standard? Or something else?


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