Gas mileage in the rain

I've noticed quite a hit in the rain, as well. I'm just guessing, but maybe the extra energy required to displace the water from between the tires and road surface does it.

 

Also, having to use the defroster. I've noticed the ICE kicks in when the defroster is going. The windshield wipers probably don't draw that much juice.

 

the extra drag cost about 1 1/2 -2 mpg loss. Living here on the wet coast in heavy rain you do notice it

 

Around here, any precip means near constant stop and go traffic.

And while that's good in small bursts in the Prius, driving 30 miles of stop and go traffic isn't so good - the ICE has to kick in to charge up the battery, but it's not being used to it's full efficency since traffic is at a crawl.

Perhaps this is also part of the problem you're encountering?

-m.

 

Jeff,

Haven't you been off work for the winter break for the past two weeks? Your driving patterns must be different.

My mileage has been about the same. I filled up yesterday and I got 48.2 on that tank. Only once, the immediately preceding tank at 52.7, did I do substantially better.

 

just went back thru my November December spread sheets and it's 2.2 Impmpg, so that's about 1.8 US mpg. That data was the difference for the month of November when it was pretty wet for almost the whole month, a few day's we had over 2 1/1" in 24 hours and the route is the same all the time. Temps were within a few degrees. Heater/ A/C settings the same and for the most part traffic patterns the same other than one day were I had to take a different route because of a serious accident that close the bridge that I normally take. It's slightly longer but at almost the same speed, traffic patterns and the same time because we always have a 1 mile crawl to the bridge the other way just drive. The slow crawl almost never gets me to S4 in the winter. Nomally get the ICE to 70C just as I get to the bridge. And if it's there before the traffic never stops completely for the 6 seconds it needs to go into S4 In the summer no problem I'm in S4 before we come to a stop.

 

I don't usually use my a/c, but lately, when the windows start to fog up in a heavy rain, I just push the auto a/c button on the steering wheel, and my windows clear very quickly. I know that's probably part of my mileage hit. Most of my driving is on the freeway. I go about 60 unless it's really raining hard, then I slow down.

 

I was going to ask the question about rain also.

Last week I had the Tire pressure set to 42/40 and had the oil change and the tires rotated. After that I was expecting to see decent strides in FE. All of last week was rainy and I was thinking that the tire pressure and/or rotation had adversely affected my MPG (I was around 52.6 and went back to about 51.2). I was expecting to get up in the 53 range with the tire pressure change.

Anyway this week no rain, no changes and I am in the 54's for my commute. Then it dawned on me that it might be the rain, and I think this confirms it.

At least I can mark of my driving skills going backwards as the cause!