Who makes an Aftermarket MPG Computer?
 

I love my 2004 Subaru STi for its dual personalities and spartan gagets but wish it had a "MPG computer" like the '08 Imprezas (and many other new cars) come with. I'm talking about the display that can tell you current or average mpg. Does anyone know of an aftermarket source for one? It would help in making the best gear selections for the times when I'm driving for efficiency (I can get approx. 30 mpg) rather than speed (160 mph @ about 3 mpg!)

just look around for about 5 minutes... scangauge is what everyone uses

I think Mega Squirt can control everything on your car and it can be programmed for economy but I honestly think its best to leave your engine management system in place and start tuning for FE instead.

^Ingore the post above, the previous guy knows what I'm talking about. I'm checking out the Scangauge now. Anyone know of others?

I think that for OBD-2 cars (like yours), it is probably the most popular choice.

There are various approaches that bypass OBD-2, and this can have certain advantages. But I think for most people the SG is a simple and effective choice. Although not super-cheap.

SG is the quickest and easiest way. It also does a lot of other really cool stuff.

For something that will look nicer and be cheaper, see if an upscale model of your car from the same generation offers a MPG gauge, then you can get it from a junkyard and have it look stock.

For ultimate accuracy in choosing gears for a given speed, look at the DIY fuel rate monitor link in my sig. The SG doesn't have access to actual fuel rate measurement data; instead, it has to guess based on air flow and O2 sensor readings.

Thanks for all the advice, especially theholycow. I think this thread can be left to die now. Maybe the next person will be better at searching than I was.

other brands?
 

Can anyone give any other brands of MPG / trip computers like the Scangage. Surely they are not the only one out there.

I use a DashDyno SPD. Besides giving fuel economy, it does data logging and 0-60 performance monitoring + lots of other stuff. I might be way better than a Scangauge, since I heard this turns off during a FAS P & G. But it's expensive at $379.

https://www.auterraweb.com/dashdynoseries.html

The DashDyno looks pretty awesome, but I think it has the same problem that SG has (as mentioned in #6). I think it does not directly read fuel use via the injectors.

Well, when the Dashdyno is calibrated it predicts my weekly tank fill, which is usually very close unless I fill up at a pump that rips me off with bad gas!

Currently, my Dashdyno's performance 0-60 screen didn't work well. Gotta email them for a fix!

If you will go to ebay and do a search on scan gauge it will bring up all the brands that anyone on there has to offer.

Setting the Scangauge to Hybrid in the fuel menu keeps it alive during EOC / FAS.

I recommend it.

Are there any pre-OBD2 fuel monitors? I think SuperMID may be, but I'm not sure, and I can't seem to find a good link for it.

There are some pre-OBDII mileage monitors but they may all be DIY electronics projects. There's a link in my sig (do I sound like a broken record?) that is very easy and not too expensive (<$40) that can at least easily show you fuel rate. It's not combined with speed so it won't show MPG, but right at the top of it I recently added links to two threads about MPG monitors based on similar technology.

Thanks for mentioning that.

I think the OBD2 approach (what's used by DashDyno and Scanguage) probably works well for most people most of the time. But I think there are certain circumstances where errors might creep in. I also think certain types of errors might tend to balance each other, which means you won't notice them when you're doing your calibration on a strictly per-tank basis (which is the main means of calibration that is typically used).

I don't want to overstate the problem, and I think there is no perfect solution that is superior. I just think it's good to be aware of this possible limitation.