MPG Gains?

Hey guys! New guy incoming. Not a motorhead, yet, so lots of stupid questions. I know just enough to be a danger to myself and to my vehicle... So... Bear with me lol.

As you may have guessed, I'm a delivery dude! Been doing it about five years, and I'm very comfortable with my life.

Lately, however, some stuff - competition - has come up that has made my pocket book uncomfortable, and I've begun looking for ways to decrease my spending, on gas in particular. 

I found a seemingly reliable dual propane conversion for about 800 that I'm gonna try out, not just for mpg but for reduced engine wear - '96 Subaru Legacy with 236K - but a lot of what I'm looking to do is reduce weight, and one thing I've (literally) got my eyes on is my windshield and various windows. They're so pitted they look foggy sometimes. 

I was wondering about the pros and cons between Lexan and Plexi, and what might better suit my needs? What I could expect from performance, aaaand if it's even feasible to use them for an  150+ mile a day, every day use vehicle?

And if you've got any other tips on improving mileage, I'd love to hear them?

Unless it's to buy a new car. I love my car. 

Tires. Forget everything until you have the right tires at the right pressure. Try to go narrower, like a 185, and use one of the new eco/green tread compounds. If you have 15's you can use Prius take offs. Air those puppies up to max recommended for the car on the doorjamb while loaded. I gained 4 MPG going from 300TW summer 245's to 600TW all-season 205's.

Second is alignment. If you're crab-walking down the road or dragging a wheel your mileage will never improve. I had 2* excess negative camber and 1/4" toe out on 1 rear tire and lost 2 MPG.

Third is mechanical losses. Make sure all of your calipers still freely return and especially your parking brake. Make sure the hub/axle bearings are good (bad rear hub bearing lost me 2 MPG). Change the oil and go with a quality, light oil. I run 0W20 full synthetic in my Mazda, gained about .5MPG doing that and the trans fluid. 

Once you've done those we'll need to talk aero. Way more gains there than weight.

And to add on to what Javelin said, lexan is horrible on the street. It becomes aware item in the span of months not years. Guarantee you the mileage increase you would see from that weight reduction would be way more than offset by the expense of continually replacing the mall. I have had good luck wet sanding and polishing glass much like you would paint to get some of those imperfections out.

Get on ecomodder.com tons of useful advice! But a couple pointers the most important thing is to monitor ur driving with a ultra gauge or scan gauge always seeing ur economy helps second a grill block reduces aerodynamic drag and helps the engine heat up faster reducing wear and helping fuel mileage. Third synthetic fluids they have less drag while cold and are a maintenance item anyway. Hope this helps

In reply to Javelin :

Well, for tires right now I'm running Winterforce 185 15's because we get really bad snow here, so winter tires are a must even though they're dragging down my MPG, but definitely something to look into for summer!

Alignment was just done, and I'm running full synth already!

Also got new sparks, ran a few bottles of cataclean and B12 through the tank for good measure. 

Mechanical wise, I just had my parking brake fully replaced, have not even consider the other bits you mentioned,  i'll get them checked monday!

In reply to Dusterbd13-michael :

What about a thicker plexi glass with a UV filter I could pop out and buff every few months as necessary??

In reply to Saturnguy :

Good resource, thank you!

Neither lexan nor plexi is DOT approved. If they do inspections of that sort of thing in your area, it will be a problem.

Strongly recommend you just stick with auto glass.

Weight really doesn't make much difference unless you are going uphill all the time.  With proper hypermiling techniques, you will be using the weight to your advantage by coasting downhills and up to stops.

As Javelin said, most of your non-aero gains will come from minimizing rolling resistance.  Keeping your speed down and drafting will also make for significant gains.  

You have to look at the payback on any modification.  $800 otherwise spent on a propane conversion would buy a lot of gas.

In reply to Will :

South Dakota. No inspections. Some truly outrageous stuff is completely street legal. 

aero, aero, and more aero after all of the maintenance, tire and mechanical stuff is addressed. 

In reply to stuart in mn :

I spend roughly $375 a month in gasoline.

If it holds true to the claim of a 30% increase in mileage, I'll ramp up to about 29 mpg city. Highway, i'll be getting around 37. 

Even factoring in the cost of propane, it will pay for itself in about 6-7 months,  and then start putting back into my pocket. And it's a simple kit - I can transfer it to any vehicle I purchase down the road. 

Plus, propane burns cleaner, and creates no carbon buildup, meaning I can stretch my oil changes out further, if I wanted, or keep them the same knowing that every mile I drive is less wear on the engine. That's an endless amount of money saved. 

The last 90's subaru I owned I got up to 475K miles before she gave up the ghost. Get rid of the 236K I have on this one, and that's 239K to go. Factor in 30% less wear and that number jumps up to another potential 310K miles. For me, that's another 25 months of work. 

That's a veritable ****ton of money saved. For 800 bucks? That's what I'd pay to put in a new water pump and half of what I'd pay to get a new timing belt.

People don't consider how much it costs to be a delivery driver. 

In reply to Cooter :

Drafting isn't much of an option, i'm not on the interstate all that much - and I live in the black hills, so yes, i'm going uphill constantly. But, i'm also going downhill constantly, so I have it in neutral all the time. 

In reply to AnthonyGS :

What are some good aero modifications I can get started on right away? 

In reply to DeliveryGuy89 :

Which means that you aren't actually going uphill all the time. And it is also is why weight won't matter than much.  Work on the basics first.

All the aero gain is under the car. Build a full belly pan front to back and look at a diffuser for the back. 

In reply to Javelin :

What about wheel skirts? Those worth the effort, or would they be a buildup hazard in the snow? And what material should I go with for a belly pan?

Definitely would not do lexan or anything other than glass.

Air your tires up to max pressure, run synthetic oil and maybe even try premium gas. On my explorer doing all 3 of those made my mpg go from 18 ish to 23 ish along with careful driving. Driving like an shiny happy person nets about 20mpg vs 17 .

On a long trip i tried premium gas and it jumped to almost 24mpg at 80mph vs 17mpg, even with the added cost it was saving me money. YMMV because my explorer is not really meant for 80mph lol

In reply to DeliveryGuy89 :I took my 2000 avalon  with 189000 miles from ave of 27 mpg to 34 mpg ( trip computer on my xls) new 205/55/16 tires and booster the pressure to 38 psi all around, still rides nice, perhaps a little sharper steering and handling ,also replaced all the rubber sway bar Bush's to polly. Forgot  67 mph in cruise control at all times

If you have a friend with a propane business like me you might be able to buy it at the home heating price and save a bunch of fuel tax. In BC I see used propane conversion kits on craigslist quite often for a couple hundred dollars.

In reply to DeliveryGuy89 :

Couple of things you can do, too- make sure you run the lightest oil for the engine.  Check the manual- it will tell you what Subaru speced out.

And when you go downhill, keep it in gear- the car will turn the fuel off.  which is better than neutral, since fuel is used to keep it running.

Also, keep your speeds down.  It's amazing how much less fuel you use between 45-55 and 55-65.  I know you are a delivery person, so time matters, but given your experience, you also know the distances you travel really well.  Do the calculation to see the time difference dropping a few MPH, find the stretches you can deal with that time, and experiment with going slower to see how much fuel you save.  Especially if you are going up hill at above 65mph- there's a good chance that the engine is going into component protection, so it's running rich just to protect itself.

Do you need the AWD your car offers?  If not, why not just trade for a Prius?  For what you do its the perfect vehicle.  

My Subaru on its best day never got close to the mileage our Prius on its worst day.

Aero mods are definitely where the big gains are, but if you are dealing with a lot of snow, they will be limited.

Speed does have quite the effect on mpgs. My 2018 Cruze gets 36-38 at 70-75 mph (rated 38 hwy) but at 55-60 mph I get 40-43 mpg. Colder weather has droppedit by 1-2 mpg.

Lexan and wipers are a bad combo, wiper will scratch the Lexan in short order. Stick with glass, most modern glass isn't all that heavy compared to older cars.

In reply to ProDarwin :

We regularly get blizzards here, with 6-14 inches of snow dropping in 3-4 hours. The most I've personally seen here is 2 feet, but there were 14 foot drifts covering entire houses in some places. This year has been relatively dry, but even the 3-4 times it has come down, it's been thick and heavy,  which leads to black ice everywhere.

You'd catch me dead in a ditch, in a Prius.

I delivered Papa John's in this. Delivery just doesn't shut down because of snow here.

Last year we had a fog at 35 F, and I watched my external thermometer drop to 27 F within 30 seconds. Was at an offramp, and everyone started to slide downhill, from a complete stop. Only myself and a dude in a big Dodge Ram that popped the curb and drove down into the flood plain avoided the resulting massive pileup at the bottom. It was ridiculous.