Stop / go traffic vs highway crawl.
 

took a different route for a while. both routes involve severe hill climbing on the return home. the new route was a lot of stop start city like traffic. it is about 2 miles shorter than my usual route but after 2 weeks my mpg plummeted! engine revs are lower here but my speed is also lower. going to stick to the usual route which is more like a highway crawl, 2nd 3rd gear stuff!

Yep, nothing like watching MPG going UP in low speed highway stop/crawl scenarios. It is even more fun watching the impatient drivers deal with it & then driving past them later on. It just doesn't get any better!!

Pop always told me, " Keep the idiots in front of you.

Works great until the car that just whipped by you tosses a connecting rod through it's own oil pan and it hits your new car in the windshield.

regards
mech

always happens! I used to ride a bike before I got my car licence and it tought me a lot in planning ahead and being in the right lane in the right time. always keeping an eye out for the car 5 cars ahead of you!

I don't have any instrumentation to give me immediate results yet I calculate my fe on each tank. fill up about 10 litres a time. that's why it took me a while to figure out I was getting worse mpg when the same 10 litres left the fuel needle nowhere near where it use to be.

first I thought its because here winter is setting in but winter here is like summer for the rest of you. morning temps rarely drop to 10 deg Celsius or 50 deg F compared to the usual 20 def mornings in summer. so I don't think its that.

At what point does going at a crawl / stop and go, out-do a faster pace with more lights ?

I would have thought that the highway crawl would be worse, because you are constantly accelerating and braking ( or coasting in our case )

The secret to low speed highway stop/crawl is you don't accelerate much. Basically a short pulse & glide with the engine on.

Too many long stops or speeds under 10 MPH will not produce satisfactory results. (unless in a hybrid)

Eddie-

You should get a gauge to track fuel consumption. Just because you get worse MPG on one route doesn't mean you consume more fuel by driving that route, especially if it's 2 miles shorter. Efficient route planning minimizes fuel consumption (not necessarily increasing MPG) and time spent driving.

As far as stop and go traffic is concerned, I get better fuel economy in gridlock than I do steady cruise on the freeway. I allow a gap to form ahead of me while I drive the average speed of traffic. When traffic is stopped, the buffer reduces, and when it moves again the buffer increases.

This might only work in Portland traffic as people don't madly change lanes like they do in SoCA. I once counted the number of cars that moved into the gap I created and subtracted the number of cars that moved back out of the gap for an hour-long drive from South Portland all the way through North Portland. The total cumulative number of cars that moved into the gap compared to those that moved out came to 13 cars in 1 hour of driving. That might have cost me an extra 20 seconds in my 3,600 second drive, or about half of 1% of my commute time. I'll gladly arrive at my destination 20 seconds later for the relaxation gained by constantly moving in traffic and gaining fuel economy

gauges are coming! the biggest problem is all the hills in my very underpowered car! coasting home is out of the question its 90% throttle and building speed for the next hill. driving to work is awesome I have almost a 17km or 10 mile coast. http://ecomodder.com/forum/showthrea...ast-31683.html
stop start I always have to use the handbrake when accelerating again. with a crawl I can leave it in gear and not lose my momentum. heres an elevation profile for the return home
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