Rain, rain, go away!
 

Friday evening I drove 180 miles and Saturday evening I drove 180 miles back. I decided I wanted to get a really good FE tank in, so I filled up fresh and whipped out my SG-I (which hadn't seen use since last fall). Unfortunately it was raining cats and dogs on Friday!

Trying to keep speed in the range 52mph-62mph in general, DWL and neutral coasting when appropriate, I found that on the way down I needed to keep LOD around 49, while on the way back (no rain!) I could keep LOD around 37! SG-I reported a difference of 10mpg (45mpg versus 55mpg, though it is about 10-15% optimistic and an early revision so not adjustable).

So I found rain to be a big hinderance to my FE! How do you guys deal with it?

Rain increases rolling resistance and aerodynamic drag. There's nothing you can do besides weight reduction, aeromods, and driving slower.

That, and make sure your engine bay stays dry enough to warm up quickly, and drive on the lowest-RR spots on the road. So, avoid standing water, and try to drive on the tire tracks of the guy in front of you.

Just put a car cover on your car when you drive.

At least wet roads give you a more widely accepted excuse to go slower. One good thing with a stick shift is you can usually slow down some in high gear and still move along just fine, where an automatic will kick you out below a certain speed.

No wonder my fuel logs look so dismal. It's raining almost daily here in Oregon. Not to mention the crosswinds on the highway I drive daily...

Or... stay home! :p :D

AeroModder -

Yup, you're getting hammered. Had a rainy day yesterday on the freeways. There is almost no way to win. As a corollary, some of the best MPG runs I got last year came during the LA forest fires, :eek: !

CarloSW2

I hear you man I'm Portland and yeah it can rain for weeks nonstop.

I've had only one tank with completely dry weather, and that one averaged 26.4 MPG. With this rain I'm struggling to hit 23.

I hear ya too, Michigan is the same way (at least the northern half of the mitt where I'm at). Probably because of all the water just like Oregon. Sometimes we get dry spells, but it's almost always overcast and when it rains it just keeps going for days or sometimes weeks. The wind is almost always cold and gusting from some direction. Every single time I go out on the highway I get pummeled by the wind. A truly warm sunny calm day is a rare occurence and is something we celebrate. I need a heavy shirt 95% of the year. But the plus side is adding clothes is easier than taking away. Then there are all the steep hills when traveling east or west from where the glaciers cut the land, and officially the 2nd worst roads in the USA. I think I do pretty good with mpg, but I always wonder what kind of mpg I could get out of the Celeb if I was in Texas or something.

A note on wet-weather driving: If the road you're on has ruts from tires rolling on it constantly, drive on the higher parts out of the ruts. The ruts will fill with water, so you'll be driving through puddles constantly. You may have to drive closer to the lane next to you, but you'll be getting less rolling resistance from pushing water out of the way and driving on a smoother surface.

Wow, it took a while to find this thread, but I wanted to find an existing one vs. starting a new one if possible. I went out to the next town today and it was raining pretty constantly (fortunately, not too common here). And while I was accustomed to my mileage increasing and increasing as the miles ticked off, I was having a helluva time getting the darned "today" average on the ScanGauge up to 21.

But the road was pretty wet, and although I instinctively tried to stay out of as much of the standing water as I could, I know I was driving mostly through water, anyway. So my question is: how much will a wet road cut your mileage? I would say it was at least "several" MPG for me ..... 21-ish vs. the 26-ish I'd grown accustomed to. I had a passenger this time too, so a couple hundred pounds more weight. Dunno if that effected it other than accelerating & going up hill. ???

A second question I forgot to put in that last post: Will operating windshield wipers add enough drag to reduce MPG? I've read the threads saying that in the "off" position, they're in a "high pressure pocket" where the relative wind doesn't really interact. But when operating, they spend a portion of their time "up" on the windshield. Just wondering how much that's worth? Probably far less than the mirrors being in the "normal" position or "folded back", I imagine. Any thoughts/knowledge?

using wipers will reduce mpg when in use the air is catching on them and now you have a higher electrical load to use them. And one thing not all wipers are in an air pocket, take a leaf and place it under the wiper if you see the leaf moving extremely then air is dragging on the wipers

Thank you, Gealii. Another thing to test - I love it!!! And this is a handy time of year to find just the right leaf!! LOL.

You know, when I got up this morning, I thought DUH!! - when a car drives on a wet road, there is a tremendous amount of spray that comes up. (I know this too well from being a surveyor standing alongside the road and witnessing this many wet times) But if you apply a little "obvious" physics, it takes energy to pump all that water into that spray - and the energy comes from the car - - energy that probably would be pumping water if there was no water, huh?

If you want it to not rain just throw out some grass seed. Works like a charm for me.

regards
Mech

And if you WANT it to rain, wash your car. :) works most of the time here. :D

me and 2 friends just washed our cars so ill get back to you on that theory:D

Don't blame it all on the water. Blame a lot of it on your increased need/want for electricity and a/c for defrost.

This past summer I did an alternator delete with two substantial deep cycle batteries to provide for all the electrical, and also an ac compressor belt delete (after the compressor seized up).

Now I don't get nearly as much of an mpg hit in rain as I used to. Yes I run down the batteries faster running headlights and fan and wipers, but fuel economy doesn't drop as badly as it used to. All that electricity and of course the a/c for defrost used to run off the engine. No more!

Having done those deletes, I can say from experience that a lot of the mpg hit due to rain is from the accessories we want to run in the rain.

I washed both cars today. It was less work than chasing the birds away that were eating the freaking grass seed. Of course I could have just put my crabby wife out on the porch and the birds would have left the country.:thumbup:

regards
Mech

Heh!!! You guys are cracking me up!!

Well, here's a bonehead manuever I just made: It's still stormy weather here, right? Rained all day yesterday, wind blowing this morning and through mid-day, and the weather forecast saying there was another storm out in the Pacific that would be hitting sometime this weekend. Right?

OK, so with all that knowledge, "Mr. Genius" here decided to go see if I could "A-B-A" test my mileage with & without windshield wipers. (I'll bet you can tell where this is headed already, huh?) Yup, you're right!!! I went out & did a series of 3 "out & back" runs for my "A" average, then stopped & took my wiper blades off & headed out again. I swear that within a half a mile, drops started appearing on my windshield!!! Well, I'm not gonna be intimidated easily, so I soldier-on. And of course, the rain got heavier. Before long, the streams of water are streaking up & over the windshield, etc, etc.

So - test aborted, wipers re-installed, and - oh, yeah - the rain stopped. !#$%^&*?!!

So there may be an alternate way to get your grass seed watered, Mech!!! (or maybe idiots just shouldn't try to do "no wiper tests" during stormy weather. HAH!!!! :rolleyes:

Oh, by the way, I DID put some leaves under my wiper blades & they were moving around. Not furiously, but moving, so I'm not too sure if I learned anything from that or not. :confused:

All I can really say is that MOST of the time our rain in these parts is a slow misty kind
which only means that the puddles aren't as deep.

If you are by yourself (not talking throwing out hot air), you can usually get by at least at a constant 45-50mpg. w/o using the fan for your defroster.

Though I'm not driving enough these days to warrant it; this would probably be the time
to throw in a plug for RainX!!!

I have always liked the '70's, and '80's cars/trucks that have the recessed wipers.
Now one of you will probably tell me that there is a reverse airflow eddy just from that lip???

Been using rain-x for close to 40 years, grumpy wife complains about me not turning on the wipers, EVEN THOUGH YOU CAN'T SEE ANY BETTER WITH THEM ON.

regards
Mech

OK, I'll show my ignorance here . . . I've never used "RainX" before. So how's it work? You spray it on your windshiled (I assume), and then it causes the rain to not blind you? What, it beads up and blows off faster or something? How about when you go to the gas station & scrub the bugs off with the squeegee? Do you need to reapply the RainX after that? Does it ever build up & cloud/fog the windshield or anything?

Another unrealted question: I have the stock clutch fan (I think) on my Jimmy. It looks like a little turbine, with like 8 blades or something, made of a milky white plastic of some sort and a really serious looking pitch on the blades. But I spun it by hand, so I guess it's that "viscous coupling" or whatever they call it. Now - is it costing me MPG by being a power parasite, and if so how much? If I just removed it, would I have problems and/or save any gas?

Thanks in advance,
Bill

Rain-x is a silicone based product that causes the water to bead really easily so you can drive without using wipers. If you live in a place that receives LOTS of rain year round, this is a very good product.

BUT: If you live someplace where it rains infrequently, has dirty and grimy roads, lots of bugs, or winter, I'd avoid using it.

I used to use it years back in the early 2000's but stopped. Using the wipers with rainx applied causes a momentary haze as the wiper passes. Bugs and their splatter caused this to worsen. Road grime and winter sand and salt cause it to become useless. All of this combined causes the haze to worsen and linger longer. I gave up on Rain-X years ago and have no desire to test it again.

However, if you live in Vancouver, BC or Seattle or the Oregon coast or some other place that sees much precipitation and no winter, then you should give Rain-X a try!

Just my observation with the product! :cool:

With the rainy season well under way in the Bay Area, I'm starting to get extremely frustrated at the amount of fogging I am getting on the windshield. One thing I heard before was using detergent on the windshield to get the water droplets to disperse, but I did this and I just got a really wet glaze on the windshield that was pretty much just as bad.

Today I went to get some drinks and junk food from Safeway and I couldn't even wipe the windshield clear with paper towels, and had to resort to turning the air conditioning on for a few minutes while parked (wasting a precious 0.02 gallons of fuel) :/

Turning up the fan works but not immediately. With the fan on though (even without air conditioning on) condensation forms on the outside of the window, although this isn't a problem since I can just have the wipers turned on.

Does anyone know of any effective anti fog measures? I suppose this is one of the good points of open cockpit track day cars and motorcycles heh.

Make sure you have the setting so that you're pulling in outside air, NOT recirc!!! Vent to the windshield, of course. Heat...

Some vehicles automatically turn the AC on when you switch the controls to windshield.

Also, buy a GOOD aerosol foaming glass cleaner and polish all the dirt away!

You can buy a good anti-fog for motorcycle faceshields, never tried one myself though.

Heat doesn't work when the engine is cold though >:/

My AC is fully manual control (on a side note, I hate auto climate control so much).

In that case, maybe I'd better pass. Around here, rain is the exception rather than the rule, but bugs, dust, and the spray from the salted/sanded roads to melt ice & help traction would force me to "wipe", anyway. Just thought of that - - better plan on keeping those blades REALLY handy if I ever do decide to go crazy & remove them, huh?

Thanks again for the info! :thumbup:

its a old story guys . Post some recent buzzes..

Sorry - - it was new to me.

I finally went out & did an A-B-A test with and without wiper blades on. My standard testing course and speed (50 mph). 3 sets of 2-way averages (northbound & southbound) for the "control", and then 3 more with the blades off. Finally, one more "control" set;

"A" stock - wiper blades on.
N.B. - S.B. - AVG
27.5 - 28.2 - 27.85
27.6 - 27.9 - 27.75
27.6 - 28.2 - 27.9 - - - 27.869

"B" wiper blades off
27.6 - 28.2 - 27.9
27.6 - 27.9 - 27.75
27.4 - 27.9 - 27.65 - - - 27.767

"A" wiper blades back on
27.3 - 28.0 - 27.65

From this, there certainly doesn't appear to be any benefit to removing the wiper blades. In fact, this tends to suggest taking the blades off makes mileage WORSE. However, since the last "control" set was the worst yet, maybe things were "trending down" for some reason. I don't know why that would be - the outside temp wasn't changing much (29 at the start, and 27 at the end), and I didn't detect any change in the wind. So, I don't know... ???

If I'd had time, I would have done another one or two "A" tests, and then maybe even another "B" test. Of course, if it's not enough to show in the way I do the tests, maybe it's not enough to consider anyway?