Maximizing MPG driving 10k miles in a rental (minivan or SUV)
 

I am planning on taking a month long cross country road trip this summer with several friends as one last adventure before we all turn 30. The route we are looking at taking is just over 7k miles but I imagine with local driving and side trips that the entire trip could come close to 10k miles in total.

There are 5 (possibly 6) of us going and we all either drive small cars or big inefficient SUVs. In addition to not having enough space the depreciation on a car after adding 10k miles just isn't worth it for any of us to drive our own cars so we are looking at rentals. Based on size requirements it is pretty much required we either get a mini-van or SUV with a mini-van being the most fuel efficient but even they get fairly poor mileage. We checked the rental rates for cities close to our starting point (Lexington, KY) and found the best deals on monthly rentals in Louisville.

Anyway, I'm posting here to try and figure out how to maximize our MPG and reduce our overall fuel cost so we can put that money towards more rewarding expenses. Considering the difference between 14-15 mpg and 20-22 mpg could be a savings of $1000 over the length of the trip it is definitely worth it to invest a couple hundred in modding/tuning the car in the beginning. So I'd like everyone's thoughts on the mods I can and can't do with a rental. I'm willing to devote quite a bit of time into reading & prepping beforehand and willing to spend a day modding/testing at the beginning of the rental.

Requirements:
Has to be 100% reversible
Risk of damage to the mini-van should be almost zero
Can take up to 1 full day to do
Can't require buying model specific parts just in case that year/model isn't what we get
Willing to spend $100-300
Needs to increase efficiency by 10% to be worthwhile

My thoughts:
1) Fold in passenger side mirror (possibly drivers side on straight highways)
2) Remove antenna and store
3) Remove wiper blades and store?
4) DIY tire covers attached using new lugs with screws drilled
5) Use of scangauge (not factoring this into cost since it can be useful to me afterward)
6) Inflate tires to max sidewall
7) Quick partial grill cover (anything better than duct tape to attach it that won't leave adhesive residue?)
8) Tape over seams in lights, grill, front bumper, maybe even hood, etc (again anything better than duct tape that won't leave residue?)
9) Oil change - will definitely do at least 1 during the trip but unsure if I should invest in one before we start to make sure oil & filters are clean

Anything I'm not thinking of? Any of those sound like a bad idea?

PS: Efficient driving will be a top priority but I'm hoping to find a few mechanical things that may help as well

Sounds like you got the basic easy to do and remove mods

as far as non residue duct tape 3M Scotch No Residue High Performance Duct Tape, 1.88-Inch by 20-Yard, 1-Pack - Amazon.com
If i ever do a kamm or wheel skirts i plan on grabbing this

If you use coroplast for wheel covers you could use zip ties to secure them, i had 5k miles on my covers held on by zip-ties b4 i removed the covers to repaint em

You should be able to use zip ties on a grill block too. Also, you might get away with screwing in an air dam, since it's underneath...ain't nobody gonna check there for little extra holes, and wouldn't know what they were if they did see them. I'd think your biggest factor will be the base vehicle...be careful, I once rented an Impala for the 31mpg thing....they gave me the Impala SS......25mpg.

Remember too, going 60mph giving yourself time to get there will put some money in your pocket rather than hammering to and fro at 75-80mph, that seems to be where a fair amount can be saved. But a challange for a bunch of younger guys, it is a definite mindset shift.

I don't think taping the seems would pay itself for the tape you'd have to use, this is an over rated aero enhancement.

maybe a grill block, some seam taping. wouldn't bother with anything else, as i doubt it would be worth the effort

if it is available, gey an odyssey with cylinder deactivization. other may have it as well by now, but, not sure. i guess the toyota with the 4 cylinder would be good also

I wouldn't mess with any of it beyond over-inflating the tires and getting agreement from everyone on board to chill and set the cruise at 50 mph.

Just check your rental agreement. Most of them start to charge you a high rate for the number of miles driven after a certain mileage. In the long run it would be cheaper to drive your own car and then you could do permanent Eco mods. Just a thought.

Oh I made sure to find a rental place with unlimited mileage and no geographical restrictions.

Considering most mini-vans are rated at 25 highway / 17 city and most of our driving will be highway what is a reasonable estimate of actual mpg without any modding and a reasonable estimate for mpg after modding?

Would a trip average of 28-30 mpg be an unreasonable goal?

While cost savings is an important factor I am also interested in seeing how far I can push the limit with cheap/temporary mods as well.

I would suggest;

1) Inflate the tires as high as you dare

2) Do a grille block & watch the temp. on your ScanGauge - block as much as you can get away with.

3) Test rear fender skirts. They may or may not help, depending on the vehicle.

4) Run a quick series of tests with the ScanGauge to see what your best MPG speed is. It might be ridiculously low, like 40 mph, but if you know this, and for every 5 mph increment up to 60 - 70 - whaterver you want to test to, you are then armed with knowledge. While you won't wanna be driving 40 on the freeways, I'm sure, if you happen to be on a street in town that has a speed limit of 30, 40, 50 - - - whatever, you can try to keep 'er at 40 at those times. (or whatever your best mpg speed happens to be). Even on the freeway, if you know you do 2 mpg better at 60 than 70, and even another 1.2 mpg better at 55, if you're not in a particular hurry, you'll know you can save gas at 55 if you're willing to drive that speed. (cruise control really helps keep from inadvertantly going faster than you want - set it & forget it) On the flip side of that coin, if you decide you ARE in a hurry & have to go 70 or higher, you'll at least know what it's costing you.

5) Taping seams and removing radio antennas is probably more trouble than it's worth. My experience with folding the mirror(s) back is the gains are real but very small - and losing the use of your mirrors can be a MAJOR hassle - especially as traffic increases. One day I tried to drive into Sacramento in the RAIN with mirrors folded back - - - WRONG!!! I pulled over quick to pop them back out. I was driving blind, traffic was all around me, and with the rain, I couldn't see squat!!!!

6) If it comes with a roof rack and you don't need it and you can get it off, THAT will save you some. - more than folding the mirrors, in my experience.

7) try to avoid loading it so the back end is "heavy" & "squatting down". This exposes more of the aerodynamically "dirty" underside to the oncoming wind and really increases drag compared to level or slightly nose-down.

They make stuff like "goof-off" that's good at removing the residue from duct tape & isn't supposed to hurt the paint. As long as you can count on it not hurting the paint, that could simplify your life. Laquer thinner is pretty good at removing that kind of goo too, but not sure what effect it would have on paint. I'm guessing you'd bo ok, but that's not the type of thing you wanna find out the "hard way"!!!

Define "reasonable". HAH!!! You could probably reach that goal with modding AND serious hypermiling driving (20 mph below the speed limit on the highway, engine off & coasting up to all stoplights, coasting down all hills in neutral or engine off, etc.)

My 2000 GMC Jimmy has a combined rating of 16, I think (18 highway). I can get the ScanGauge to read 30, but that's at 40 mph with the roof rack off, mirrors folded in, full grille block, and tires at 60 psi). It would be pretty "hard-core" to do a 10,000 mile trip like that!!! But by bumping the speed up to 50 mph, I can still get, like 26-27 mpg, so that might be a better compromize. With that car, folding both mirrors only yielded about 0.15 mpg. - and losing about half my rear visibility is a pretty big price to pay for that!!!!

Ok I may ignore the mirrors then if the benefit doesn't match the added risk/hassle.

wmjinman: You Jimmy is rated 17 mpg combined and you got 24 mpg that is an increase of ~40%. A grand caravan (and most other vans) are rated for 23 combined. Would only need a 30% increase to hit 30mpg. I know it is pushing it but with good driving and a few mods I think that could be attainable (from what I've been reading).

On the issue of roof racks, if the van comes with cross bars I had planned on removing them but what about just the bars running front to back? Do those make much difference if there are no crossbars?

I've read a few aero projects on here and am debating having a good amount of coroplast on hand before picking up the mini-van. Not sure what the best balance of time/effort vs mileage increase would be though. I think a belly pan is out of the question but an air dam on the front or just flaps for both sets of tires may not be.

I think I will also cover the wipers with coroplast instead of trying to take them off. Not sure if I will try and leave it short enough so the wipers can still function without taking it off or whether I will extend it all the way to the window to try and smooth that transition.

Also in regards to tire pressure. Some of the newer vans have tire pressure sensors and I was wondering about the max pressure I could inflate them before setting it off and also whether a rental car company could/would check something like that?

Thinking outside the box for a minute, maybe the best modification you could do would be to take two small (and economical) cars? You also get the benefit of being able to make separate side trips, send one person into town for supplies, etc.

Two small vehicles could make sense as the rental companies sometimes rent their econoboxes very cheaply. But if there are going to be many tolls/parking expenses, better to stay with a single vehicle.

I considered taking 2 vehicles but the cost was more than a benefit.

From an existing vehicle perspective we could save rental fees but would be adding 10k miles to personal vehicles which would add maintanence costs and depriciation in resell value. The only options in personal vehicles would be a 2010 taurus or 2002 Camaro, neither of which are that great an improvement over a rented mini-van in mpg.

From a rental perspective at first I thought it may be a better deal considering most Econo cars are ~$600-650 for a monthly rental and most mini-vans were double that. I happened to shop around enough to find a monthly mini-van rental with unlimited mileage for $980 after tax. So an Econo car would need to get more than 2x the mileage to justify it based on price + fuel costs alone.

Storage in small economy cars may be an issue as well, even with 2. We plan on visiting several national parks and camping in the area so we will probably have a fair amount of extra equipment in addition to a month of normal clothing, etc. With a mini-van it is possible to store/remove one of the middle seats to increase storage space, keep weight balanced, and still fit 5-6 comfortably. Not to mention that several camping places may limit # of vehicles per site and a national park yearly pass covers an entire carload so would need 2 with 2 vehicles.

I created a spreadsheet with vehicle rental rates, epa mpg ratings, and fuel costs for every rental vehicle available and calculated per person total based on a comfortable number of passengers. The best value is a full sized 15 passenger van loaded with 12 people and rear seat removed for storage but we won't have that many people. A Nissan Versa or Ford Focus are both great values but only hold 4-5 so we would need 2 and could have storage issues; it may work if we had 8 people going though. After that comes to deal I found on a Grand Caravan. For 5-6 people it seems like the most economical option.

When I took the roof rack off my Jimmy, I just did the whole thing in one whack, so I don't know how much the cross bars were vs. the longitudinal ones. But from reading the various posts on here, I'm guessing the cross bars are where most of it is - so the gains from doing the rest of it might be minimal.

I'd say experiment with folding the mirrors in. Just 'cuz I didn't see a great improvement doesn't mean it won't be in the van you get. But when you approach congestion, be prepared to either pop them back out, or for it to get "hairy"!!!

On the tires, I guess the "prudent" thing would be to put them to max sidewall & then make sure the tire pressure sensor alarm doesn't go off. If it does, adjust until it goes back off, right?

I didn't look too closely at my Jimmy's percentages vs. what your goal was, so sorry about that. I guess the point I was trying to make was just that EXTREME improvements can be had, but it may take EXTREME efforts to do it! - like driving everywhere at 40 mph!!! But yeah, if my gas logs are showing 40% over EPA, and you wanna get 30% over, then I guess the "shot in the dark guess" would be you could probably do it while being LESS extreme than I was. - and my tanks did include at least 2 or 3 cold starts per day, and probably at least 30% "city" driving with stoplights, etc.

Belly pan - yeah, probably a huge effort for a rental car. I plan to do one for my own car, but due to the huge effort, I haven't done it yet! LOL!!! And I've read a couple reports on here where guys went to all that trouble and then were very dissappointed by seeing much smaller gains than they expected. - That would kinda suck!!

Windshield wipers - don't be surprised if you don't see any improvement. From what I hear, it's miniscule, at best. It's pretty dry where I live, so we can go a week or more without rain. So I thought I'd do an A-B-A test with the blades off vs. on in the Jimmy. - Didn't see any difference at all .... exact same averages both ways. I haven't tried the test on my Swift yet. The way it's hood/windshield interface is shaped, I think there might be more of a chance to see a difference there, so gotta test that.

Air dam - I'd say it depends on what your van looks like when you get it. If you can squat down a few dozen feet in front of it & see all kinds of lumpy machinery hanging down below the line of whatever smooth front end it has - AND - you can figure out a way to attach it without going into "major engineering/manufacturing mode", then yeah - it'll probably help you. If not, then it might not. Hard to say. One of those "play it by ear" things.

You know, if your co-horts are all into the hypermiling thing, you guys could have a really fun game by competing against each other to see who's tank "wins" with the highest MPG. That would tend to keep you all on your toes.