I've been noticing that the first drive of the day (engine cold) tends to net somewhat lower fuel economy, especially as compared to the mileage I get if I drive 5-10 miles (enough to get the engine thoroughly warmed up), then stop (engine off) and then drive some more.

I specifically was watching for this today: the real-time meter on the car indicated 34.5 MPG from my house to the gas station (about ten miles), where I stopped to fuel up. From the station to work (another 25 miles or so), the meter indicated 40.8 MPG. The outside temp when I left home was 16°F.

I've noticed this effect going both ways, so it's not like I'm benefiting from a 'downhill to work, uphill back' situation or anything.

Anyone else noticing this effect?

es

 

Will certainly take not of this when and if our temperature drops to match what you are currently experiencing (must admit I hope that doesn't happen anytime soon!!)

16F!!! Great Gobs of Oogity-Boogity! That's cold!

I don't suppose ROTTBOY will be responding to this thread ... on permanent vacation in paradise.

 

That's normal. A cold engine burns more fuel by design. Everything about the engine is designed to run at warm temperatures, so it burns more fuel at the start to hurry up the warming process.

Mini-experiment: cold start fuel consumption and warm-up time - MetroMPG.com

 

Yes, that seems normal. Hence its also recommended to generally drive continuously in the mornings and do the stops for errands later, when the engine has warmed up.

 

I'm familiar with the fact a cold engine burns more fuel than a warm one (which is consistent with what I saw this morning), but my experience seems to indicate something else going on. I've noticed the MPG difference even after the car has sat in the parking lot for hours - the next drive gets 3-5 MPG better mileage for some reason.

Will keep monitoring. It's not a huge deal - more of a curiosity than anything.

es

 

How about this (taken last winter)?



Until we moved to the Middle West, the coldest I'd ever seen was +9°F (Atlanta, GA).

es

 

You learned that electrical plug on the diesel truck wasn't for battery charging?

 

Minnesota got into the -40's last year...
Thank god my wife graduated med school and moved back to California.

 

I hit -10F last year during the winter. Of course my companies Ontario facility got colder than that

 

Oh okay ... then i will look forward what you find or others mention

 

Sitting in a parking lot for hours (however weak the sunlight) doesn't cool the system down more than sitting overnight does, so all else being equal, the morning run will be with a colder start and lower mpg.

 

I thought my fuel economy got nailed this week. Two morning the temps were below 15F and driving into a nasty headwind. I couldn't believe my eyes when my average MPG was like 25, which is usually around 29-30.

 

I made a 17 hour trip last Sunday, and my average (my calculation) was only about 35 - was expecting over 40! Temps were in the high 20s when I left, high 40s where I arrived, with light to moderate rain for about 9-10 hours of the trip.

This afternoon, I took the car to the local Honda dealer here, where they addressed a low-speed odd noise by removing a rock from my brake rotor splash shield - I'm wondering if it was causing enough drag to affect mileage... Will see when I make the return trip.

es

 

I'm just curious, what was your typical speed? Since I've been monitoring my MPG, I've found that wind direction makes a big difference. In my Corolla, which I typically get 29-31 MPG at ~70 MPH, I can get 38 MPG by driving 60 MPH and having a tailwind. But it's also a 3-speed transmission with the overdrive being a 1:1 ratio.

 

Given that my hooning days are well behind me, I pretty much drive the posted speed limit. Most of my trip was interstates, so 65 or 70 MPH, with some 55 stretches at either end. There was some wind, but I don't remember it being severe.

I did end up sitting completely stopped (engine off) for about an hour on I-24 West of Chattanooga - bad accident had all EB lanes closed.

es

 

Could have impressed the drivers when you use the "refresh" mode in the car. lol

Yeah, sucks traffic and accidents these days are getting worse. Seems DOT are behind in upgrading our roads.

 

Its averaging fuel consumption even when your not moving....

 

Which is why I shut down when traffic stopped. Having the truth stare you in the face (zero MPG averaging into your real-time stats) was an eye-opener!

es

 

It's one of the cool features of my old 2012 Civic Hybrid. It shuts the engine down whenever it's at idle and immediately starts up when I lift off the brake pedal. It uses the electric motor / generator in the engine to start it up. It also has a traditional starter only used if the big battery does not have enough juice. I'd imagine the starter was never used. lol