Greetings! This thread is about my GD7 that I'm calling an "Eco Rat". Eco as in economical, although I suppose a little ecology is sprinkled in. Rat as in function will take precedence over form. I intend to document my DIY repairs and modifications here. Full disclosure: I'm not an expert and I don't know what I'm doing . Hopefully this will be useful to someone, and feedback is always welcome.

Goals:
1. Get the total cost of ownership down to $80 per month (currently near $300 per month)
2. Keep the car on the road until 2026
3. Obtain 70mpg average fuel economy
4. Retain cargo carrying and one passenger capabilities

What I did in 2021 (regrettably I didn't take any pictures of this work):
1. Replace rear bumper beam (rusted out)
2. Weld rusted section of rear frame
3. Mounted and balanced new tires
4. New front dampers (kept old springs and such)
5. Engine oil, filter, gear oil change (I used 10w40 conventional oil in the gear box and noticed extremely stiff shifting in the winter)

What I've done this year so far:
1. 280 lbs weight reduction (11.5%). I plan to post a followup with the details on this
2. Changed the gear oil to 10w30 synthetic. Hopefully this performs better in the cold
3. More frame welding on the rear
4. Fiber filler repairs in the floor



Driver side rear foot well fiber filler repair

 

How did you save 280lbs? Just tossing all the interior? Even so, I don't really see 70mpg happening unless you swap in a small diesel engine or something. Best I ever managed was around 45mpg in what was almost the best case of lots of 90km/h highway driving with no traffic. Good luck though, I'd be happy to be proven wrong

 

I get all tingly when a man starts talking about reducing vehicle weight. I wish I could strip out my Fit and just have the driver's seat and a sun visor, but it wouldn't be practical for me at the moment.

@GGG You are probably not worrying about this, but removing significant weight will change the balance of the car. I wonder how a stripped out car will feel on the road and if you will need to change your suspension. Just a thought.

 

Why use 10w30 engine oil? Why not use Manual Transmission oil? Am I missing something here?

 

Oh wow, I misread that and thought the plan was to change from 10w30 motor oil. I guess it's supposed to be some hypermiling hack but there's a good reason gear oil is its own thing.

 

Most of the interior is gone. I've started stripping the engine bay, underside, and exterior as well. I agree that 70mpg is unlikely, but I wanted a good challenge. Best tank to date was last tank at only 40.9mpg.

 

So far the handling doesn't feel much different, but I'm not done cutting weight yet. I will try to keep an eye on it.

 

@mobby_6kl @Mister Coffee As for using motor oil in the gear box, the owners manual says 10w30 or 10w40 is ok. It is cheaper and more readily available then the official honda stuff.

 

No disrespect, but I still wouldn't do this. Oil is all about the additives in the oil. Application specific oil should be used for specific applications. But if you are in the game to save money, then you are in the vast majority, and my arguments don't matter much.

Note: I'm not an expert oil or anything else. I'm just some guy on the Internet.

 

Yeah the manual also says
I mean I skipped on the Honda MTF too for my beater because it's more expensive than unicorn tears but you can get Gl4 75W-80 oil from Shell or Castrol for not much more than motor oil. You only need like 1.5 liters anyway, and it will last forever. I think it would be worthwhile considering you're trying to get the best efficiency, the gear oil would be designed specifically to make the transmission work as efficiently and reliably as possible.

 

Again, if you like to save money on cars and car maintenance, then you are in the vast majority. My position is that I like to spend money on my cars and motorcycles, and the Fit's MT gearbox is one of the best features of the car. I want the gearbox to have the best possible fluid.

I save money by not buying food. Where I live, food is more expensive than MT fluid and unicorn tears.

 

Sure, my Miata gets also the proper stuff too, the 20 year old, $600 econobox that will be 50% iron oxide in a few years gets whatever will work Everyone has different priorities and that's fine though.

In this specific case it was about using the correct type and grade of oil, which IMO would be a big step up compared to seeking out the magical Honda specific stuff. There's always a point of diminishing returns I seriously doubt the Hond stuff is going to make any difference in this case.

Anyway, GGG, what's your driving like? A lot of highway I assume if you're hoping to average 70mpg? The biggest wins will probably be from aerodynamics then, something like this might be necessary

 

@mobby_6kl My driving is mostly city driving, especially since the pandemic. With regard to MPG, I don't think much about it. I just like driving the car, and if I want to pin the tach needle at redline, I do it (and laugh my head off the whole time).

I really like Miatas. I think an 2015 MC would have been good for me.

 

A mix of highway and country roads. Not too much city driving. Agreed that aero mods will be required to hit my target. I plan to eventually do a partial grill-block, under-tray, external side mirror delete, wheel skirts / smooth hubs, and partial boat tail / kammback.

 

I've been busy the past two weeks. Last week I replaced the passenger side CV axle and passenger side inner + outer tie rod. Did the oil seal while I was doing the axle and no longer leaking gear oil.



9 more pounds removed from the rear end.

Freshly painted hatch release (please excuse the focus).

 

One of my favorite projects on youtube has a new goal of swapping a small diesel engine into a Saturn. Something to keep an eye on to see if he can hit 70 mpg

 

Neato! thanks for the recommendation. I'm just working on keeping the car on the road at the moment. It needs a steering rack replacement. I'm trying my luck with Detroit Axle since it's 1/8th the cost as from the dealership.

 

Hey, how's the project going?

They got the Saturn diesel working, and got 56mpg in their test which as far as I understand is mostly driving at constant speeds.


I'm sure it could be improved a bit with aerodynamics and it'd be interesting to see if adding a turbo makes things better or worse. The engine is running at close to maximum output which is usually good for the efficiency.

 

@mobby_6kl I got distracted with other things. Still a few weight removal ideas to tackle but I'm getting pretty close to the limit of free mods in this area. I don't want to spend replacing parts with lightweight versions. In the next couple of weeks I would like to weigh the car and install some aero mods. Fuel economy has been lousy this winter and I think the engine needs a tune-up.